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Professor Derek Eamus

Biography

Derek Eamus is a plant physiologist and ecophysiologist who has worked mostly on tree species for the past 15 years. For the decade 1990-2000 he worked on savanna ecophysiology, through the CRC for Tropical Savannas and the Northern Territory University. He has been keen to have projects that integrate measurements over several spatial scales. For example, his lab has undertaken measurements of leaf scale processes (photosynthesis and transpiration) and leaf scale attributes (specific leaf area, foliar Nitrogen content, cost-benefit analyses of leaves); tree-scale processes and attributes (whole tree water-use; growth rate, allometric relationships; hydraulic architecture and xylem embolism); stand –scale processes and attributes (canopy exchange of water and CO2; leaf area index) and catchment scale processes (vegetation and groundwater interactions). He was appointed to the Chair of Environmental Sciences at UTS in 2000 where he continues his interests in plant physiology, ecophysiology and ecohydrology, working at cellular, whole organism and ecosystem scales.

Derek leads the Terrestrial Ecohydrology Research Group within the School of Life Sciences

Image of Derek Eamus
Professor, School of Life Sciences
BSc (Hons) (UK), PhD (Wales)
 
Phone
+61 2 9514 4154

Research Interests

  • CO2 and water flux measurements of leaves and canopies
  • Comparative analyses of groundwater dependent ecosystems
  • Measuring and modelling ecosystem function

Summary of past work
  • Stomatal physiology and function
  • Climate change impacts on tree physiology
  • Hydraulic architecture of trees
  • Eco-hydrology of savannas
  • Plant stress physiology

Can supervise: Yes
Students and topics - Rhys Whitley - modelling water and C exchange from woody landscapes - Sepideh Zolfaghar - a comparative study of the ecophysiology of groundwater dependent ecosystems

Derek's principle areas for teaching are Plant Physiology and Ecophysiology (91270) and a new subject on Ecohydrology to be offered from 2011 onwards. He regularly gives talks to postgraduate students on "how to write your thesis" and "how to write a journal article" for science students. His lab regularly includes Honours, Masters and PhD students working on a range of ecophysiological and ecohydrological studies at sites scattered across Australia.

Textbooks
Derek was the lead and principal author of the textbook entitled (Ecohydrology: vegetation function, water and resource management" published by CISRO (2006).
Derek was also co-editor and a major contributor to award winning text book "Plants in Action", (MacMillan Press). He has also co-written a chapter on north Australian Ecology for an Oxford University Press book on Australian Ecology (2001).

Books

Eamus, D., Hatton, T., Cook, P. & Colvin, C. 2006, Ecohydrology: Vegetation Function, Water and Resource Management, 1, CSIRO Publishing, Collingwood, VIC Australia.
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This book is not a textbook on Australian ecology. The purpose of this text is to reveal and discuss the links between vegetation function and water in landscapes - that is, to discuss ecohydrology.We focus primarily (but not exclusively) on the interactions among the woody components of vegetation, rainfall and changes in groundwater availability.Woody vegetation is the focus because of the centrality of changes in woody vegetation cover to the ecohydrology of Australia over the past 100 to 200 years. Furthermore we focus on vegetation function (ecophysiology) rather than structure, because it is the functioning of vegetation that influences hydrology inthe first instance. Although this book uses Australian examples,the principles, philosophy and methodological approach are applicable worldwide.
EAMUS, D. & JARVIS, P.G. 2004, The Direct Effects of Increase in the Global Atmospheric CO2 Concentration on Natural and Commercial Temperate Trees and Forests.
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Assessing the Impact of the Rise in CO2: A doubling of the present atmospheric CO2 concentration is likely to occur by the end of the next century and will have many effects on trees and forests. There may be major changes in climate, especially temperature and precipitation, that will affect the growth and ecology of trees and forests: there will be substantial effects on the growth and ecology of trees and forests as a result of the direct effects of CO2 on the physiology of trees. To a considerable extent the consequences of an increase in atmospheric CO2 concentration on climate are speculative, whereas many of the direct effects of an increase in CO2 concentration on the physiology and growth of plants have been established through experimentation and are quite well known and understood. There are several reasons for showing active concern about the consequences of the rise in CO2 concentration for trees and forests: to enhance knowledge, at a fundamental level, about the functioning of woodlands and forests; to assess the likely impact on their ecology, productivity and value; and to anticipate any significant downstream, socio-economic consequences. The consequences of the rise in CO2 concentration may be assessed at a range of temporal and spatial scales: from seconds to centuries, from cell to region. Biological information about the effects of CO2 on plants is generally available at short time scales and small spatial scales, whereas ecological and socio-economic concern is largely expressed with respect to the much larger scales of the stand and the forest over tens or hundreds of years. There are major problems with the data currently available. The environmental conditions pertaining in the majority of the experiments (e.g. soil type, temperature) differ significantly from forest conditions throughout the boreal and temperate regions. Secondly, the use of juvenile trees in growth cabinets and rooms makes extrapolation to the field situation difficult...

Chapters

Yunusa, I.A., Veeragathipillai, M., Burchett, M., Eamus, D. & Skilbeck, G. 2007, 'Utilisation of coal combustion products in agriculture' in Gurba, L., Heidrich, C. & Ward, C. (eds), Coal Combustion Products Handbook, Cooperative Research Centre for Coal in Sustainable Development, Australia, pp. 374-409.
Eamus, D. & Christian, K. 2003, 'Monsoonal Tropical Australia' in Attiwill, P. & Wilson, B. (eds), Ecology: an Australian Perspective, Oxford University Press, Melbourne, Australia, pp. 315-331.
Eamus, D. & Ceulemans, R. 2001, 'Effects of Greenhouse Gasses on the Gas Exchange of Forest Trees' in Karnosky, D.F. & Ceulemans, R. (eds), The Impact of Carbon Dioxide and Other Greenhouse Gasses on Forest Ecosystem, CABI International, Wallingford, UK, pp. 17-56.
Eamus, D. 2000, 'Some Tree Responses to CO2 Enrichment' in Singh, S.N. (ed), Trace Gas Emissions and Plants, Kluwer Academic Publishers, Netherlands, pp. 75-95.

Conferences

Ali, M.M., Al-Ani, A., Eamus, D. & Tan, D.K. 2013, 'An Algorithm Based on the RGB Colour Model to Estimate Plant Chlorophyll and Nitrogen Contents', 2013 International Conference on Sustainable Environment and Agriculture, 2013 International Conference on Sustainable Environment and Agriculture, International Association of Computer Science & Information Technology Press, Abu Dhabi, UAE, pp. 52-56.
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Leaf colour gives a good indication of chlorophyll (Ch) and nitrogen (N)status in plants. In this paper we developed a new, easy to use and non-destructive diagnostic approach to detect plantCh and N levels using an image processing technique developed using the RGB (Red, Green and Blue) colour model. The experiment was conducted on tomato (Tommy Toy) in field with three N treatments (0, 60 and 140 kg N / ha), where leaf images were collected using a handheld scanner. The new algorithm achieves superior correlation with the value of Ch and N, measured in laboratory, compared with the existing non-destructive methods of SPAD 502 and Dark green Colour Index (DGCI ).
Huete, A., Eamus, D., Ma, X., Restrepo-Coupe, N., Boulain, N. & Hutley, L. 2011, 'MONITORING PHENOLOGICAL VARIABILITY ACROSS A TROPICAL SAVANNA ARIDITY GRADIENT WITH REMOTE SENSING ACROSS SEASONAL TO ANNUALAND EXTREME EVENTS', ISPRS BHOPAL 2011 WORKSHOP EARTH OBSERVATION FOR TERRESTRIAL ECOSYSTEM, pp. 19-19.
Yunusa, I.A., Fuentes, S., Merrick, N.P. & Eamus, D. 2009, 'Hydrological control on a waste management site', EcoForum 2009, EcoForum 2009, EcoForum, Sydney, Australia.
Yunusa, I., Whitley, R., Zeppel, M., Eamus, D. & IEEE 2009, 'Simulation of Evapotranspiration and Vadose Zone Hydrology Using Limited Soil Data A comparison of Four Computer Models', PROCEEDINGS OF THE SECOND INTERNATIONAL CONFERENCE ON ENVIRONMENTAL AND COMPUTER SCIENCE, pp. 152-155.
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Yunusa, I.A., Veeragathipillai, M., Skilbeck, G. & Eamus, D. 2008, 'Amelioration of soil physical properties and enhancement of root growth with coal fly ash.', Soil â the living skin of the planet earth, Soil â the living skin of the planet earth, Australia and New Zealand joint Soil Science Societies, Massey University, Palmerston North, New Zealand, pp. 1-3.
Yunusa, I.A., Veeragathipillai, M., Burchett, M., Skilbeck, G. & Eamus, D. 2007, 'Australian fly-ashes as an agronomic resource: progress and new opportunities', Contamination Clean-up 07, Adelaide, Australia.
Yunusa, I.A., Veeragathipillai, M., Eamus, D. & Skilbeck, G. 2006, 'Economic and environmental advantages of using fly ash as a soil amendment in agronomy', Environmental Science, Ecosystems & Development: Proceedings of the 5th WSEAS International Conference on Environment, Ecosystems and Development, WSEAS International Conference on Environment, Ecosystems and Development, World Scientific and Engineering Academy and Society, Tenerife, Spain, pp. 294-302.
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Yunusa, I.A., Eamus, D., De Silva, D.L., Murray, B., Burchett, M., Skilbeck, G. & Heidrich, C. 2005, 'Prospects for coal-ash in the management of Australian soils', World of Coal Ash Proceedings, World of Coal Ash 2005, Coal ash Association and the University of Kentucky's Centre for Applied Energy Research, Lexington, USA, p. CD ROM.
Yunusa, I.A., De Silva, D.L., Odeh, I. & Eamus, D. 2004, 'Imbalance water-use in farming systems: the potential for bamboo', Salinity Solutions Conference, Salinity Solutions Working with Science, CRC Dryland Salinity, Bendigo, Australia, pp. 1-5.
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Currently there are few perennials that can maintian all-season water-use and provide ongoing economic benefit in dryland cropping systems. The effectiveness of lucerne in clayey soils and in high rainfall environments has been inconsistent, while the economic potential of native woody species is still uncertain. We suggest in this short discussion the need to explore the use of suitable bamboo species for their rapid growth rates and, hence, water requirement, as well as for their economic benefits. Furthermore, from their morphology we expect bamboos to have a greater capability to open-up dence subsoils to benefit other crops in rotations than the herbaceous species. Out limited undertsnading of the physiology of bamboos is recognised as a major knowledge-gap.
Eamus, D. & Prichard, H. 1998, 'A cost-benefit analysis of leaves of four Australian savanna species', TREE PHYSIOLOGY, pp. 537-545.
EAMUS, D. & NARAYAN, A. 1990, 'ROOT LP AND ION-TRANSPORT RESPONSES TO DROUGHT, CHILLING AND ABA', IMPORTANCE OF ROOT TO SHOOT COMMUNICATION IN THE RESPONSES TO ENVIRONMENTAL STRESS, pp. 288-289.

Journal articles

Eamus, D., Chen, C., Cleverly, J., Zhang, L. & Yu, Q. 2016, 'Modelling Seasonal and Inter-annual Variations in Carbon and Water Fluxes in an arid zone Acacia savanna woodland 1981 - 2012', Ecosystems, vol. 19, no. 2, pp. 625-644.
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Changes in climatic characteristics such as seasonal and inter-annual variability may affect ecosystem structure and function, hence alter carbon and water budgets of ecosystems. Studies of modelling combined with field experiments can provide essential information to investigate interactions between carbon and water cycles and climate. Here we present a first attempt to investigate the long-term climate controls on seasonal patterns and inter-annual variations in water and carbon exchanges in an arid-zone savanna-woodland ecosystem using a detailed mechanistic soil-plant-atmosphere model (SPA), driven by leaf area index (LAI) simulated by an ecohydrological model (WAVES) and observed climate data during 19812012. The SPA was tested against almost three years of eddy covariance flux measurements in terms of gross primary productivity (GPP) and evapotranspiration (ET). The model was able to explain 80% and 71% of the variability of observed daily GPP and ET, respectively. Long-term simulations showed that carbon accumulation rates and ET ranged from 20.6 g C m-2 mon-1 in the late dry season to 45.8 g C m-2 mon-1 in the late wet season, respectively, primarily driven by seasonal variations in LAI and soil moisture. Large climate variations resulted in large seasonal variation in ecosystem water-use efficiency (eWUE). Simulated annual GPP varied between 146.4 and 604.7 g C m-2 yr-1. Variations in annual ET coincided with that of GPP, ranging from 110.2 to 625.8 mm yr-1. Annual variations in GPP and ET were driven by the annual variations in precipitation and vapour pressure deficit (VPD) but not temperature. The linear coupling of simulated annual GPP and ET resulted in eWUE having relatively small year-to-year variation.
Santini, N.S., Cleverly, J., Faux, R., Lestrange, C., Rumman, R. & Eamus, D. 2016, 'Xylem traits and water-use efficiency of woody species co-occuriring in the Ti Tree Basin arid zone', Trees: structure and function, vol. 30, no. 1, pp. 295-303.
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The hydraulic niche separation theory proposes that species co-exist by having a range of traits to allow differential access to resources within heterogeneous environments. Here, we examined variation in branch xylem anatomy and foliar carbon stable isotopes (13C) as a measure of water-use efficiency (WUE) in seven co-occurring species, Acacia aneura, Acacia bivenosa, Corymbia opaca, Eucalyptus camaldulensis, Erythrina vespertilio, Hakea sp., and Psydrax latifolia, in an arid zone open Corymbia savanna on the Ti Tree Basin, Northern Territory, Australia. We test the following hypotheses: (1) Species with large conductive areas exhibit a low density of intact branches, while species with small conductive areas have a significantly higher density of intact branches. (2) Species with smaller conductive areas exhibit more enriched values of 13C and therefore have larger WUE than those with larger conductive areas and (3) there is an inverse correlation between theoretical sapwood hydraulic conductivity and vessel implosion resistance. The results of this study demonstrated significant variation in density of intact branches, ranging from 0.38 to 0.80 g cm3 and this variation was largely explained by variation in sapwood conductive area. Species with low conductive areas (P. latifolia, Hakea sp. and Acacia species) exhibited large values of WUE (r 2 = 0.62, p < 0.05). These species are likely to be less vulnerable to cavitation by having small conductive areas and thicker fibre walls. We demonstrated a significant (r 2 = 0.83, p = 0.004) negative correlation between theoretical sapwood hydraulic conductivity and vessel implosion resistance. These results are discussed in relation to hydraulic niche separation.
Cleverly, J., Eamus, D., Van Gorsel, E., Chen, C., Rumman, R., Luo, Q., Coupe, N.R., Li, L., Kljun, N., Faux, R., Yu, Q. & Huete, A. 2016, 'Productivity and evapotranspiration of two contrasting semiarid ecosystems following the 2011 global carbon land sink anomaly', AGRICULTURAL AND FOREST METEOROLOGY, vol. 220, pp. 151-159.
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Ali, M., Al-Ani, A., Eamus, D. & Tan, D. 2016, 'Leaf Nitrogen Determination Using Non-Destructive Techniques – A Review', Journal of Plant Nutrition.
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The optimisation of plant nitrogen-use-efficiency (NUE) has a direct impact on increasing crop production by optimising use of nitrogen fertiliser. Moreover, it protects environment from negative effects of nitrate leaching and nitrous oxide production. Accordingly, nitrogen (N) management in agriculture systems has been major focus of many researchers. Improvement of NUE can be achieved through several methods including more accurate measurement of foliar N contents of crops during different growth phases. There are two types of methods to diagnose foliar N status: destructive and non-destructive. Destructive methods are expensive and time-consuming as they require tissue sampling and subsequent laboratory analysis. Thus, many farmers find destructive methods to be less attractive. Non-destructive methods are rapid and less expensive but are usually less accurate. Accordingly, improving the accuracy of non-destructive N estimations has become a common goal of many researchers, and various methods varying in complexity and optimality have been proposed for this purpose. This paper reviews various commonly used non-destructive methods for estimating foliar N status of plants.
Cleverly, J., Eamus, D., Luo, Q., Coupe, N.R., Kljun, N., Ma, X., Ewenz, C., Li, L., Yu, Q. & Huete, A. 2016, 'The importance of interacting climate modes on Australia's contribution to global carbon cycle extremes', SCIENTIFIC REPORTS, vol. 6.
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Cleverly, J.R. & Eamus, D. 2016, 'Droughts and flooding rains: it takes three oceans to explain Australia's wild 21st-century weather', The Conversation.
Zhao, W., Liu, B., Chang, X., Yang, Q., Yang, Y., Liu, Z., Cleverly, J. & Eamus, D. 2016, 'Evapotranspiration partitioning, stomatal conductance, and components of the water balance: A special case of a desert ecosystem in China', Journal of Hydrology, vol. 538, pp. 374-386.
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&copy; 2016 Elsevier B.V. Partitioning evapotranspiration (ET) into its components reveals details of the processes that underlie ecosystem hydrologic budgets and their feedback to the water cycle. We measured rates of actual evapotranspiration (ETa), canopy transpiration (Tc), soil evaporation (Eg), canopy-intercepted precipitation (EI), and patterns of stomatal conductance of the desert shrub Calligonum mongolicum in northern China to determine the water balance of this ecosystem. The ETa was 251 &plusmn; 8 mm during the growing period, while EI, Tc, and Eg accounted for 3.2%, 63.9%, and 31.3%, respectively, of total water use (256 &plusmn; 4 mm) during the growing period. In this unique ecosystem, groundwater was the main water source for plant transpiration and soil evaporation, Tc and exceeded 60% of the total annual water used by desert plants. ET was not sensitive to air temperature in this unique desert ecosystem. Partitioning ET into its components improves our understanding of the mechanisms that underlie adaptation of desert shrubs, especially the role of stomatal regulation of Tc as a determinant of ecosystem water balance.
Zhuang, W., Cheng, L., Whitley, R., Shi, H., Beringer, J., Wang, Y., He, L., Cleverly, J.R., Eamus, D. & Yu, Q. 2016, 'How energy and water availability constrain vegetation water-use along the North Australian Tropical Transect', International Journal of Plant Production, vol. 10, no. 3, pp. 403-424.
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Cleverly, J.R., Eamus, D., Restrepo Coupe, N., Chen, C., Maes, W., Li, L., Faux, R., Santini, N.S., Rumman, R., Yu, Q. & Huete, A. 2016, 'Soil moisture controls on phenology and productivity in a semi-arid critical zone', Science of the Total Environment.
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Cleverly, J., Eamus, D., Restrepo Coupe, N., Chen, C., Maes, W., Li, L., Faux, R., Santini, N.S., Rumman, R., Yu, Q. & Huete, A. 2016, 'Soil moisture controls on phenology and productivity in a semi-arid critical zone', Science of the Total Environment.
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&copy; 2016 Elsevier B.V. The Earth's Critical Zone, where physical, chemical and biological systems interact, extends from the top of the canopy to the underlying bedrock. In this study, we investigated soil moisture controls on phenology and productivity of an Acacia woodland in semi-arid central Australia. Situated on an extensive sand plain with negligible runoff and drainage, the carry-over of soil moisture content () in the rhizosphere enabled the delay of phenology and productivity across seasons, until conditions were favourable for transpiration of that water to prevent overheating in the canopy. Storage of soil moisture near the surface (in the top few metres) was promoted by a siliceous hardpan. Pulsed recharge of above the hardpan was rapid and depended upon precipitation amount: 150mm storm-1 resulted in saturation of above the hardpan (i.e., formation of a temporary, discontinuous perched aquifer above the hardpan in unconsolidated soil) and immediate carbon uptake by the vegetation. During dry and inter-storm periods, we inferred the presence of hydraulic lift from soil storage above the hardpan to the surface due to (i) regular daily drawdown of in the reservoir that accumulates above the hardpan in the absence of drainage and evapotranspiration; (ii) the dimorphic root distribution wherein most roots were found in dry soil near the surface, but with significant root just above the hardpan; and (iii) synchronisation of phenology amongst trees and grasses in the dry season. We propose that hydraulic redistribution provides a small amount of moisture that maintains functioning of the shallow roots during long periods when the surface soil layer was dry, thereby enabling Mulga to maintain physiological activity without diminishing phenological and physiological responses to precipitation when conditions were favourable to promote canopy cooling.
Karan, M., Liddell, M., Prober, S., Arndt, S., Beringer, J., Boer, M., Cleverly, J., Eamus, D., Grace, P., van Gorsel, E., Hero, J.-.M., Hutley, L., Macfarlane, C., Metcalfe, D., Meyer, W., Pendall, E., Sebastian, A. & Wardlaw, T. 2016, 'The Australian SuperSite Network: a continental, long-term terrestrial ecosystem observatory', Science of the Total Environment.
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Macinnis-Ng, C.M.O., Zeppel, M.J.B., Palmer, A.R. & Eamus, D. 2016, 'Seasonal variations in tree water use and physiology correlate with soil salinity and soil water content in remnant woodlands on saline soils', Journal of Arid Environments, vol. 129, pp. 102-110.
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&copy; 2016 Elsevier Ltd.Ecophysiological studies of remnant woodlands in saline environments are scarce. We investigated seasonal fluctuations in soil water and salinity together with leaf and branch traits (area-based maximum assimilation (Amax), foliar nitrogen, specific leaf area (SLA) and Huber value (Hv)) and sap velocities of Eucalyptus macrorhyncha at four semi-arid sites in south-eastern Australia. Summer and winter soil salinities (10 cm depth) were 15-35 dS m-1 and 8-10 dS m-1 respectively. Gravimetric soil water content in the upper 20 cm was 2-5% in summer and 7-23% in winter, resulting in a significant inverse correlation between soil water and soil salinity. We found significant correlations between soil conditions and plant traits and function across seasons. Soil water content was significantly correlated with foliar N, SLA, Hv and maximum sap velocity while soil salinity was significantly correlated with Amax, Hv and maximum sap velocity. Correlations indicate co-variation of soil conditions and plant physiology in response to environmental conditions such as solar radiation and vapour pressure deficit (D). E. macrorhyncha tolerates the dual stresses of high salinity and low soil water during summer. While the plants appeared unhealthy, our data show that remnant vegetation can remain functional even in close proximity to saline scalds.
Beringer, J., Hutley, L.B., Abramson, D., Arndt, S.K., Briggs, P., Bristow, M., Canadell, J.G., Cernusak, L.A., Eamus, D., Edwards, A.C., Evans, B.J., Fest, B., Goergen, K., Grover, S.P., Hacker, J., Haverd, V., Kanniah, K., Livesley, S.J., Lynch, A., Maier, S., Moore, C., Raupach, M., Russell-Smith, J., Scheiter, S., Tapper, N.J. & Uotila, P. 2015, 'Fire in Australian savannas: from leaf to landscape', GLOBAL CHANGE BIOLOGY, vol. 21, no. 1, pp. 62-81.
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Togashi, H.F., Prentice, I.C., Evans, B.J., Forrester, D.I., Drake, P., Feikema, P., Brooksbank, K., Eamus, D. & Taylor, D. 2015, 'Morphological and moisture availability controls of the leaf area-to-sapwood area ratio: analysis of measurements on Australian trees', ECOLOGY AND EVOLUTION, vol. 5, no. 6, pp. 1263-1270.
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Lin, Y.-.S., Medlyn, B.E., Duursma, R.A., Prentice, I.C., Wang, H., Baig, S., Eamus, D., Resco de Dios, V., Mitchell, P., Ellsworth, D.S., Op de Beeck, M., Wallin, G., Uddling, J., Tarvainen, L., Linderson, M.-.L., Cernusak, L.A., Nippert, J.B., Ocheltree, T., Tissue, D.T., Martin-St Paul, N.K., Rogers, A., Warren, J.M., De Angelis, P., Hikosaka, K., Han, Q., Onoda, Y., Gimeno, T.E., Barton, C.V.M., Bennie, J., Bonal, D., Bosc, A., Loew, M., Macinins-Ng, C., Rey, A., Rowland, L., Setterfield, S.A., Tausz-Posch, S., Zaragoza-Castells, J., Broadmeadow, M.S.J., Drake, J.E., Freeman, M., Ghannoum, O., Hutley, L.B., Kelly, J.W., Kikuzawa, K., Kolari, P., Koyama, K., Limousin, J.-.M., Meir, P., Lola da Costa, A.C., Mikkelsen, T.N., Salinas, N., Sun, W. & Wingate, L. 2015, 'Optimal stomatal behaviour around the world', NATURE CLIMATE CHANGE, vol. 5, no. 5, pp. 459-464.
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Yunusa, I.A.M., Eamus, D., Taylor, D., Whitley, R., Gwenzi, W., Palmer, A.R. & Li, Z. 2015, 'Partitioning of turbulent flux reveals contrasting cooling potential for woody vegetation and grassland during heat waves', QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, vol. 141, no. 692, pp. 2528-2537.
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Zolfaghar, S., Villalobos-Vega, R., Cleverly, J. & Eamus, D. 2015, 'Co-ordination among leaf water relations and xylem vulnerability to embolism of Eucalyptus trees growing along a depth-to-groundwater gradient', TREE PHYSIOLOGY, vol. 35, no. 7, pp. 732-743.
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Apgaua, D.M.G., Ishida, F.Y., Tng, D.Y.P., Laidlaw, M.J., Santos, R.M., Rumman, R., Eamus, D., Holtum, J.A.M. & Laurance, S.G.W. 2015, 'Functional Traits and Water Transport Strategies in Lowland Tropical Rainforest Trees', PLOS ONE, vol. 10, no. 6.
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Shanafield, M., Cook, P.G., Gutierrez-Jurado, H.A., Faux, R., Cleverly, J. & Eamus, D. 2015, 'Field comparison of methods for estimating groundwater discharge by evaporation and evapotranspiration in an arid-zone playa', JOURNAL OF HYDROLOGY, vol. 527, pp. 1073-1083.
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Zolfaghar, S., Villalobos-Vega, R., Zeppel, M. & Eamus, D. 2015, 'The hydraulic architecture of Eucalyptus trees growing across a gradient of depth-to-groundwater', FUNCTIONAL PLANT BIOLOGY, vol. 42, no. 9, pp. 888-898.
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Ma, X., Huete, A., Moran, S., Ponce-Campos, G. & Eamus, D. 2015, 'Abrupt shifts in phenology and vegetation productivity under climate extremes', Journal of Geophysical Research: Biogeosciences, vol. 120, no. 10, pp. 2036-2052.
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Amplification of the hydrologic cycle as a consequence of global warming is predicted to increase climate variability and the frequency and severity of droughts. Recent large-scale drought and flooding over numerous continents provide unique opportunities to understand ecosystem responses to climatic extremes. In this study, we investigated the impacts of the early 21st century extreme hydroclimatic variations in southeastern Australia on phenology and vegetation productivity using Moderate Resolution Imaging Spectroradiometer Enhanced Vegetation Index and Standardized Precipitation-Evapotranspiration Index. Results revealed dramatic impacts of drought and wet extremes on vegetation dynamics, with abrupt between year changes in phenology. Drought resulted in widespread reductions or collapse in the normal patterns of seasonality such that in many cases there was no detectable phenological cycle during drought years. Across the full range of biomes examined, we found semiarid ecosystems to exhibit the largest sensitivity to hydroclimatic variations, exceeding that of arid and humid ecosystems. This result demonstrated the vulnerability of semiarid ecosystems to climatic extremes and potential loss of ecosystem resilience with future mega-drought events. A skewed distribution of hydroclimatic sensitivity with aridity is of global biogeochemical significance because it suggests that current drying trends in semiarid regions will reduce hydroclimatic sensitivity and suppress the large carbon sink that has been reported during recent wet periods (e.g., 2011 La Ni&ntilde;a).
Cleverly, J., Thibault, J.R., Teet, S.B., Tashjian, P., Hipps, L.E., Dahm, C.N. & Eamus, D. 2015, 'Flooding Regime Impacts on Radiation, Evapotranspiration, and latent energy fluxes over groundwater-dependent riparian cottonwood and saltdedar forests', Advances in Meteorology, vol. 2015, pp. 1-14.
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Radiation and energy balances are key drivers of ecosystem water and carbon cycling. This study reports on ten years of eddy covariance measurements over groundwater-dependent ecosystems (GDEs) in New Mexico, USA, to compare the role of drought and flooding on radiation,water, and energy budgets of forests differing in species composition (native cottonwood versus nonnative saltcedar) and flooding regime. After net radiation (700&#8211;800Wm2), latent heat flux was the largest energy flux, with annual values of evapotranspiration exceeding annual precipitation by 250&#8211;600%. Evaporative cooling dominated the energy fluxes of both forest types, although cottonwood generatedmuch lower daily values of sensible heat flux (<5MJm2 d1). Drought caused a reduction in evaporative cooling, especially in the saltcedar sites where evapotranspiration was also reduced, but without a substantial decline in depth-to-groundwater. Our findings have broad implications on water security and the management of native and nonnative vegetation within semiarid southwestern North America. Specifically, consideration of the energy budgets of GDEs as they respond to fluctuations in climatic conditions can inform the management options for reducing evapotranspiration and maintaining instream flow, which is legally mandated as part of interstate and international water resources agreements.
Eamus, D., Zolfaghar, S., Villalobos-Vega, R., Cleverly, J. & Huete, A. 2015, 'Groundwater-dependent ecosystems: recent insights from satellite and field based studies', Hydrology and Earth System Sciences, vol. 19, pp. 4229-4256.
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Groundwater-dependent ecosystems (GDEs) are at risk globally due to unsustainable levels of groundwater extraction, especially in arid and semi-arid regions. In this review, we examine recent developments in the ecohydrology of GDEs with a focus on three knowledge gaps: (1) how do we locate GDEs, (2) how much water is transpired from shallow aquifers by GDEs and (3) what are the responses of GDEs to excessive groundwater extraction? The answers to these questions will determine water allocations that are required to sustain functioning of GDEs and to guide regulations on groundwater extraction to avoid negative impacts on GDEs. We discuss three methods for identifying GDEs: (1) techniques relying on remotely sensed information; (2) fluctuations in depth-to-groundwater that are associated with diurnal variations in transpiration; and (3) stable isotope analysis of water sources in the transpiration stream. We then discuss several methods for estimating rates of GW use, including direct measurement using sapflux or eddy covariance technologies, estimation of a climate wetness index within a Budyko framework, spatial distribution of evapotranspiration (ET) using remote sensing, groundwater modelling and stable isotopes. Remote sensing methods often rely on direct measurements to calibrate the relationship between vegetation indices and ET. ET from GDEs is also determined using hydrologic models of varying complexity, from the White method to fully coupled, variable saturation models. Combinations of methods are typically employed to obtain clearer insight into the components of groundwater discharge in GDEs, such as the proportional importance of transpiration versus evaporation (e.g. using stable isotopes) or from groundwater versus rainwater sources. Groundwater extraction can have severe consequences for the structure and function of GDEs. In the most extreme cases, phreatophytes experience crown dieback and death following groundwater drawdown.We provide a brief...
Eamus, D. & Cleverly, J.R. 2015, 'Australia's role in the 2011 global carbon sink anomaly', Australasian Science, vol. 36, no. 4, pp. 18-19.
Yu, Q., Li, L., Luo, Q., Eamus, D., Xu, S., Chen, C., Wang, E., Liu, J. & Nielsen, D.C. 2014, 'Year patterns of climate impacts on wheat yields', International Journal of Climatology, vol. 34, pp. 518-528.
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Rainfall, temperature, and solar radiation are important climate factors, which determine crop growth, development and yield from instantaneous to decadal scales. We propose to identify year patterns of climate impact on yield on the basis of rain and non-rain weather. There are inter-related impacts of climatic factors on crop production within a specific pattern. Historical wheat yield data in Queensland during 18892004 were used. The influence of meteorological conditions on wheat yields was derived from statistical yield data which were detrended by 9-year-smoothing averages to remove the effects of technological improvements on wheat yields over time. Climate affects crop growth and development differently over different growth stages. Therefore, we considered the climate effects at both vegetative and reproductive stages (before and after flowering date, respectively) on yield. Cluster analysis was employed to identify the year patterns of climate impact. Five patterns were significantly classified. Precipitation during the vegetative stage was the dominant and beneficial factor for wheat yields while increasing maximum temperature had a negative influence. Crop yields were strongly dependent on solar radiation under normal rainfall conditions.
Zhu, J., Yu, J., Wang, P., Yu, Q. & Eamus, D. 2014, 'Variability in groundwater depth and composition and their impacts on vegetation succession in the lower Heihe River Basin, north-western China', Marine and Freshwater Research, vol. 65, pp. 206-217.
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Plant-community structure and groundwater attributes were investigated in Ejina Delta in north-western China to understand spatial variability of groundwater depth and composition and their impacts on vegetation succession. Geostatistical methods and ordination analysis were performed to analyse the data. In addition, we tried to obtain vegetation successional series by using an approach of spatial sequences instead of temporal sequences. The findings of the present study were as follows: (1) the coefficient of variation for groundwater depth (GWD), salinity (SAL), total dissolved solids (TDS), electrical conductivity (EC), pH, Ca2&thorn; , Mg2&thorn; , K &thorn; , Na &thorn; , SO4 2 , HCO3 , NO3 , Cl and F ranged from 0.04 to 1.53; (2) GWD, Mg2&thorn; , TDS, EC, Ca2&thorn; , HCO3 , NO3 and pH showed strong spatial autocorrelation, whereas K &thorn; and SAL showed moderate spatial autocorrelation; (3) canonical correspondence analysis revealed that groundwater heterogeneity, especially GWD, followed by pH, SAL, TDS, EC and HCO3 , had an important impact on vegetation succession, and thus showed a prevalence of groundwater attributes-based niche differentiation among plant communities; and (4) there were two vegetation successional processes (drought and salinisation) in the lower Heihe River Basin, and salinisation processes increased with drought processes. Our results indicated that high spatial variability of groundwater attributes contributes to promoting maintenance of species and landscape diversity in the lower Heihe River Basin.
Cheng, L., Zhang, L., Wang, Y.-.P., Yu, Q. & Eamus, D. 2014, 'Quantifying the effects of elevated CO2 on water budgets by combining FACE data with an ecohydrological model', ECOHYDROLOGY, vol. 7, no. 6, pp. 1574-1588.
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Duursma, R.A., Barton, C.V.M., Lin, Y.-.S., Medlyn, B.E., Eamus, D., Tissue, D.T., Ellsworth, D.S. & McMurtrie, R.E. 2014, 'The peaked response of transpiration rate to vapour pressure deficit in field conditions can be explained by the temperature optimum of photosynthesis', AGRICULTURAL AND FOREST METEOROLOGY, vol. 189, pp. 2-10.
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Chen, C., Eamus, D., Cleverly, J., Boulain, N., Cook, P., Zhang, L., Cheng, L. & Yu, Q. 2014, 'Modelling vegetation water-use and groundwater recharge as affected by climate variability in an arid-zone Acacia savanna woodland', JOURNAL OF HYDROLOGY, vol. 519, pp. 1084-1096.
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Verma, P., II, L.S.P., Eamus, D. & Daly, E. 2014, 'Root water compensation sustains transpiration rates in an Australian woodland', ADVANCES IN WATER RESOURCES, vol. 74, pp. 91-101.
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Ma, X., Huete, A., Yu, Q., Restrepo-Coupe, N., Beringer, J., Hutley, L.B., Kanniah, K.D., Cleverly, J. & Eamus, D. 2014, 'Parameterization of an ecosystem light-use-efficiency model for predicting savanna GPP using MODIS EVI', REMOTE SENSING OF ENVIRONMENT, vol. 154, pp. 253-271.
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Zolfaghar, S., Villalobos-Vega, R., Cleverly, J., Zeppel, M., Rumman, R. & Eamus, D. 2014, 'The influence of depth-to-groundwater on structure and productivity of Eucalyptus woodlands', AUSTRALIAN JOURNAL OF BOTANY, vol. 62, no. 5, pp. 428-437.
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Cheng, L., Zhang, L., Wang, Y.-.P., Yu, Q., Eamus, D. & O'Grady, A. 2014, 'Impacts of elevated CO2, climate change and their interactions on water budgets in four different catchments in Australia', JOURNAL OF HYDROLOGY, vol. 519, pp. 1350-1361.
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Cheng, L., Zhang, L., Wang, Y.P., Yu, Q. & Eamus, D. 2014, 'Quantifying the effects of elevated CO2 on water budgets by combining FACE data with an ecohydrological model', Ecohydrology, vol. 7, no. 6, pp. 1574-1588.
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&copy; 2014 John Wiley & Sons, Ltd. Response of leaf area index (LAI) is the key determinant for predicting impacts of the elevated CO2 (eCO2) on water budgets. Importance of the changes in functional attributes of vegetation associated with eCO2 for predicting responses of LAI has rarely been addressed. In this study, the WAter Vegetation Energy and Solute (WAVES) model was applied to simulate ecohydrological effects of the eCO2 at two free-air CO2 enrichment (FACE) experimental sites with contrasting vegetation. One was carried out by the Oak Ridge National Laboratory on the forest (ORNL FACE). The other one was conducted by the University of Minnesota on the grass (BioCON FACE). Results demonstrated that changes in functional attributes of vegetation (including reduction in specific leaf area, changes in carbon assimilation and allocation characteristics) and availability of nutrients are important for reproducing the responses of LAI, transpiration and soil moisture at both sites. Predicted LAI increased slightly at both sites because of fertilization effects of the eCO2. Simulated transpiration decreased 105% at ORNL site and 138% at BioCON site because of reduction in the stomatal conductance. Predicted evaporation from interception and soil surface increased slightly (<10mmyear-1) at both sites because of increased LAI and litter production, and increased soil moisture resulted from reduced transpiration. All components of run-off were predicted to increase because of significant decrease in transpiration. Simulated mean annual evapotranspiration decreased about 87% and 108%, and mean annual run-off increased about 111% (593mmyear-1) and 95% (376mmyear-1) at the ORNL and BioCON FACE sites, respectively.
Whitley, R.J., Taylor, D.T., Macinnis-Ng, C.M., Zeppel, M.J., Yunusa, I.A., O'Grady, A., Froend, R., Medlyn, B. & Eamus, D. 2013, 'Developing an empirical model of canopy water flux describing the common response of transpiration to solar radiation and VPD across five contrasting woodlands and forests', Hydrological Processes, vol. 27, no. 8, pp. 1133-1146.
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A modified Jarvis&frac12;Stewart model of canopy transpiration (Ec) was tested over five ecosystems differing in climate, soil type and species composition. The aims of this study were to investigate the model's applicability over multiple ecosystems; to determine whether the number of model parameters could be reduced by assuming that site-specific responses of Ec to solar radiation, vapour pressure deficit and soil moisture content vary little between sites; and to examine convergence of behaviour of canopy water-use across multiple sites. This was accomplished by the following: (i) calibrating the model for each site to determine a set of site-specific (SS) parameters, and (ii) calibrating the model for all sites simultaneously to determine a set of combined sites (CS) parameters. The performance of both models was compared with measured Ec data and a statistical benchmark using an artificial neural network (ANN). Both the CS and SS models performed well, explaining hourly and daily variation in Ec. The SS model produced slightly better model statistics [R2?=?0.75&frac12;0.91; model efficiency (ME)?=?0.53&frac12;0.81; root mean square error (RMSE)?=?0.0015&frac12;0.0280?mm h-1] than the CS model (R2?=?0.68&frac12;0.87; ME?=?0.45&frac12;0.72; RMSE?=?0.0023&frac12;0.0164?mm h-1). Both were highly comparable with the ANN (R2?=?0.77&frac12;0.90; ME?=?0.58&frac12;0.80; RMSE?=?0.0007&frac12;0.0122?mm h-1). These results indicate that the response of canopy water-use to abiotic drivers displayed significant convergence across sites, but the absolute magnitude of Ec was site specific.
Lv, J., Wang, X., Zhou, Y., Qian, K., Wan, L., Eamus, D. & Tao, Z. 2013, 'Groundwater-dependent distribution of vegetation in Hailiutu River catchment, a semi-arid region in China', Ecohydrology, vol. 6, no. 1, pp. 142-149.
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In arid and semi-arid regions, groundwater availability is one of the controls on vegetation distribution. This groundwater-dependent distribution of vegetation has been particularly observed in the Hailiutu River catchment, a semi-arid region in North China. We used remote sensing images of vegetation index (normalized difference vegetation index, NDVI) and field data of depth to water table (DWT) to assess the response of vegetation distribution on increase of DWT at the regional scale. The frequency distribution curves of NDVI with respect to different DWT were obtained. The statistical distributions of NDVI values at different DWT intervals indicate that higher vegetation coverage and more plant diversity exist at places of shallow groundwater. Both the mean and the standard deviation of NDVI values decrease with the increase of groundwater depth when DWT is less than 10?m. Beyond that depth, a low level of vegetation coverage and diversity is maintained. Comparisons of different sub-areas within the region with different dominant species showed that the NDVI of shrubs is sensitive to DWT. In contrast, NDVI of herbs is not significantly influenced by DWT. The relationship between NDVI and groundwater depth in farmlands could not be reliably determined because of disturbance by human activities. We conclude that application of this methodology may significantly improve our ability on sustainable management of land and groundwater resources.
Yunusa, I.A., Veeragathipillai, M., Harris, R., Lawrie, R., Pal, Y., Quiton, J.T., Bell, R. & Eamus, D. 2013, 'Differential growth and yield by canola (Brassica napus L.) and wheat (Triticum aestivum L.) arising from alterations in chemical properties of sandy soils due to additions of fly ash', Journal of the Science of Food and Agriculture, vol. 93, pp. 995-1002.
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Background There is a need for field trials on testing agronomic potential of coal fly ash to engender routine use of this technology. Two field trials were undertaken with alkaline and acidic fly ashes supplied at between 3 and 6 Mg ha1 to acidic soils and sown to wheat and canola at Richmond (Eastern Australia) and to wheat only at Merredin (Western Australia). Results Ash addition marginally (P< 0.10) raised the pH in the top soil layers at both sites. The exceptionally dry season at both sites constrained yields and thwarted any likelihood of gaining yield benefits from ash-induced improvements in soil conditions. Yield improvements due to ash addition were absent at Merredin and only marginal at Richmond, where no elevated accumulation of B, Mo, Se, P or S in either the straw or seeds of wheat was observed; canola increased accumulation of Mo and Se in its shoot with acidic fly ash, but it was well below phyto toxic levels. Simulations of wheat using APSIM at Richmond over a 100-year period (19092008) predicted yield increases in 52% of years with addition of ash at 3.0 Mg ha1 compared with 24% of years with addition of ash at 6.0 Mg ha1. The simulated yield increases did not exceed 40% over the control with addition of 6 Mg ha1 ash, but was between 40% and 50% with an addition rate of 3 Mg ha1. Conclusion We found no evidence of phytotoxicity in either crop in this unusually dry year and there is still a need for further field assessment in years with favourable rainfall to enable development of clear recommendations on fly ash rates for optimum yield benefits
Zhu, J., Yu, J., Wang, P., Yu, Q. & Eamus, D. 2013, 'Distribution patterns of groundwater-dependent vegetation species diversity and their relationship to groundwater attributes in northwestern China', Ecohydrology, vol. 6, no. 2, pp. 191-200.
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The study of the patterns of plant species diversity and the factors influencing these patterns is the basis of ecology and is also fundamental to conservation biology. Groundwater-dependent vegetation (GDV) must have access to groundwater to maintain their growth and function, and this is especially common in arid and semi-arid regions, including north-western China. In this paper, plant species diversity and groundwater attributes (composition and depth) were investigated in 31 plots in the Ejina Delta in north-western China to determine whether groundwater attributes influenced patterns species diversity in GDV. Detrended canonical correspondence analyses and generalised additive models were performed to analyse the data. A total of 29 plant species were recorded in the 31 plots; perennial herbs with deep roots had an advantage over all other groups, and GDV species diversity was primarily affected by groundwater depth (GWD), salinity (SAL) and total dissolved solids (TDS), HCO3, Ca2+, pH, and SO42. The herb layer species diversity and total species diversity reached their maximum in similar, moderate environmental conditions. The diversity of the tree species was influenced by SAL and TDS and was maximal at large values of GWD and low values of SAL and TDS. The diversity of shrub species was affected by Ca2+ and Mg2+ and was maximal low GWD and high SAL and TDS. Patrick's and ShannonWiener's index of the total community diversity presented a bimodal pattern along gradients of GWD and SAL, whilst Simpson's and Pielou's index showed a partially unimodal pattern. On the basis of field investigation and the analysis of field data, we concluded that the perfect combination of GWD and SAL for GDV species diversity is 2m and 1 center dot 8gl1, respectively. The appropriate combination range is 25m and 1 center dot 84 center dot 2gl1, and the critical combination for the damaged GDV species diversity is 5m and 4 center dot 2gl1.
Ponce Campos, G.E., Moran, M.S., Huete, A., Zhang, Y., Bresloff, C., Huxman, T.E., Eamus, D., Bosch, D.D., Buda, A.R., Gunter, S.A., Heartsill Scalley, T., Kitchen, S.G., McClaran, M.P., McNab, W.H., Montoya, D.S., Morgan, J.A., Peters, D.P., Sadler, E.J., Seyfried, S. & Starks, P.J. 2013, 'Ecosystem resilience despite large-scale altered hydroclimatic conditions', Nature, vol. 494, pp. 349-353.
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Climate change is predicted to increase both drought frequency and duration, and when coupled with substantial warming, will establish a new hydroclimatological model for many regions1. Large-scale, warm droughts have recently occurred in North America, Africa, Europe, Amazonia and Australia, resulting in major effects on terrestrial ecosystems, carbon balance and food security2, 3. Here we compare the functional response of above-ground net primary production to contrasting hydroclimatic periods in the late twentieth century (19751998), and drier, warmer conditions in the early twenty-first century (20002009) in the Northern and Southern Hemispheres. We find a common ecosystem water-use efficiency (WUEe: above-ground net primary production/evapotranspiration) across biomes ranging from grassland to forest that indicates an intrinsic system sensitivity to water availability across rainfall regimes, regardless of hydroclimatic conditions. We found higher WUEe in drier years that increased significantly with drought to a maximum WUEe across all biomes; and a minimum native state in wetter years that was common across hydroclimatic periods. This indicates biome-scale resilience to the interannual variability associated with the early twenty-first century droughtthat is, the capacity to tolerate low, annual precipitation and to respond to subsequent periods of favourable water balance. These findings provide a conceptual model of ecosystem properties at the decadal scale applicable to the widespread altered hydroclimatic conditions that are predicted for later this century. Understanding the hydroclimatic threshold that will break down ecosystem resilience and alter maximum WUEe may allow us to predict land-surface consequences as large regions become more arid, starting with water-limited, low-productivity grasslands.
Eamus, D., Cleverly, J.R., Boulain, N.P., Grant, N.M., Faux, R. & Villalobos-Vega, R. 2013, 'Carbon and water fluxes in an arid-zone Acacia savanna woodland: An analyses of seasonal patterns and responses to rainfall events', Agricultural and Forest Meteorology, vol. 182-183, no. 3-4, pp. 225-238.
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The study of landscape gas exchange in arid and semi-arid regions is less common than those of more mesic environments, despite their large geographical extent, their importance to regional climate, their socioeconomic values and the carbon and water balances of such regions. In this study we used eddy covariance measurements to examine net ecosystem exchange and water fluxes of a landscape dominated by a N-fixing tree (Acacia aneura; Mulga) as a function of soil moisture content, vapour pressure deficit, leaf area index and pulses of rain. Seasonal budgets of carbon and water, ecosystem-scale water-use-efficiency (the ratio of net ecosystem exchange to evapotranspiration) and inherent water-use-efficiency (ecosystem water-use-efficiency vapour pressure deficit) were also examined. Across the 12 month study, the landscape was a net sink for carbon, despite prolonged periods of zero rain.
Ma, X., Huete, A., Yu, Q., Restrepo Coupe, N., Davies, K.P., Broich, M., Ratana, P., Beringer, J., Hutley, L.B., Cleverly, J.R., Boulain, N.P. & Eamus, D. 2013, 'Spatial patterns and temporal dynamics in savanna vegetation phenology across the North Australian Tropical Transect', Remote Sensing Of Environment, vol. 139, no. 1, pp. 97-115.
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The phenology of a landscape is a key parameter in climate and biogeochemical cycle models and its correct representation is central to the accurate simulation of carbon, water and energy exchange between the land surface and the atmosphere. Whereas biogeographic phenological patterns and shifts have received much attention in temperate ecosystems, much less is known about the phenology of savannas, despite their sensitivity to climate change and their coverage of approximately one eighth of the global land surface. Savannas are complex assemblages of multiple tree, shrub, and grass vegetation strata, each with variable phenological responses to seasonal climate and environmental variables. The objectives of this study were to investigate biogeographical and inter-annual patterns in savanna phenology along a 1100 km ecological rainfall gradient, known as North Australian Tropical Transect (NATT), encompassing humid coastal Eucalyptus forests and woodlands to xeric inland Acacia woodlands and shrublands. Key phenology transition dates (start, peak, end, and length of seasonal greening periods) were extracted from13 years (20002012) of Moderate Resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI) data using Singular Spectrum Analysis (SSA). Two distinct biogeographical patterns in phenology were observed, controlled by different climate systems. The northern (mesic) portion of the transect, from 12&deg;S, to around 17.7&deg;S, was influenced by the Inter-Tropical Convergence Zone (ITCZ) seasonal monsoon climate system, resulting in strong latitudinal shifts in phenology patterns, primarily associated with the functional response of the C4 grass layer.
Morales, P.K., Yunusa, I.A., Lugg, G., Li, Z., Gribben, P.E. & Eamus, D. 2013, 'Belowground eco-restoration of a suburban waste-storage landscape: Earthworm dynamics in grassland and in a succession of woody vegetation covers', Landscape And Urban Planning, vol. 120, no. 1, pp. 16-24.
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Restoration of belowground ecology is seldom a priority in designing revegetation strategies for disturbed landscapes. We determined earthworm abundance and diversity in a 16-year old grass sward (grassland), a 6-year old (Plantation-04) and a 4-year old (Plantation-06) plantation, both of mixed woody species, on a reclaimed waste disposal site, and in nearby remnant woodland, in suburban Sydney, Australia. While no catches were made in autumn, more earthworms were found in spring (21 &plusmn; 8.6 m2) than in winter (10.2 &plusmn; 5.9 m2) or summer (14.4 &plusmn; 5.5 m2). Earthworm abundance in spring was in the order grassland Plantation-04 (35.2 m2) > woodland (12.8 m2) > Plantation-06 (0.8 m2). None of the revegetated covers had restored earthworm diversity to levels found in the woodland. Exotic species, mostly Microscolex dubius, dominated in the four vegetation covers at any time; the only two native species (Heteroporodrilus sp. and Megascoleceides sp.) found were in the woodland. We also assessed how quality of the evolving soils from the three revegetated covers, compared with that from the woodland, impacted viability of common exotic earthworm species. Both weight gain and cocoon production by the exotic earthworms were higher in the soil from Plantation-04 than in soils from the other vegetation covers, including the woodland; the two variables were positively correlated with the pH and mineral nutrient content (as indicated by electrical conductivity that was in turn correlated with clay content) of the soil. Age of vegetation rather than its composition explained differences in the level of earthworm recovery observed.
Eamus, D., Yunusa, I.A., Taylor, D.T. & Whitley, R.J. 2013, 'Design of store-release covers to minimize deep drainage in the mining and waste-disposal industries: results from a modelling analyses based on ecophysiological principles', Hydrological Processes, vol. 27, no. 26, pp. 3815-3824.
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Sustainable long-term storage of municipal waste and waste rock from mining activities in waste dumps (either above or below the land surface) requires minimization of percolation of rainwater into and then through stored waste material. There has been increasing attention given to the use of store-release covers (transpirational covers) to achieve this. However, the design of such covers remains problematic because of the unique combinations of weather, vegetation composition, soils and their interactions that determine the efficacy of each design that could be available for the construction of the covers. The aim of the work described here was to use ecophysiological knowledge of soil-plant-atmosphere (SPA) interactions through the application of a detailed mechanistic model of the SPA continuum. We examined the relative influence of soil depth, soil texture, leaf area index and rainfall as determinants of rates of evapotranspiration and water budget for several different theoretical cover designs. We show that minimizing deep drainage requires a cover that has the following attributes: (i) a water storage capacity that is large enough to store the volume of water that is received as rainfall in above-average wet months/seasons; (ii) a root distribution that explores the entire depth of the cover; (iii) a leaf area index that is present all year sufficient to evapotranspire monthly rainfall; and (iv) takes into account the intra-annual and inter-annual variability in rainfall and other climatic variables that drive ET
Chen, C., Greene, A.M., Robertson, A.W., Baethgen, W.E. & Eamus, D. 2013, 'Scenario development for estimating potential climate change impacts on crop production in the North China Plain', International Journal of Climatology, vol. 33, no. 15, pp. 3124-3140.
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It is important to investigate potential changes in temperature, precipitation and solar radiation for assessing the impacts of future climate change on agricultural production for specific regions. In this study, climate scenarios of precipitation, temperature and solar radiation for the North China Plain (NCP) were constructed in terms of stochastic daily weather sequences. A nonhomogeneous hidden Markov model (NHMM) was used to downscale daily precipitation projections at 32 stations during winter wheat and summer maize growing seasons for a baseline (19662005) and a 21st century (20802099) A1B scenario, using selected general circulation models (GCMs). A climatological seasonal cycle of regional-averaged daily reanalysis precipitation was used as input to the down-scaling for the baseline simulation; this input was then scaled by the precipitation changes from GCM projections to generate down-scaled stochastic simulations of precipitation in the 21st century. Temperature was generated using a weakly stationary generating process, conditional on precipitation occurrence, with 21st century additive changes taken from the GCMs at the regional scale. Three hypotheses about changes in solar radiation (-20%, 0% and 20%) were made considering the large uncertainty in its future change. The down-scaled simulations exhibit station increases in the mean daily rainfall of 13.969.7% in the scenarios driven by the GCM with the projected largest and multi-model mean precipitation increase for the wheat season, with changes of 0.429.9% for the maize season. In the scenario driven by the GCM with the largest projected precipitation decrease, the simulated rainfall decreases at all stations, with changes ranging from -24.6 to -0.1% for the wheat and maize seasons, respectively. Temperature increases by about 3.7?&deg;C for the wheat season and 3.6?&deg;C for the maize season.
Eamus, D., Boulain, N.P., Cleverly, J.R. & Breshears, D.D. 2013, 'Global change-type drought-induced tree mortality: vapor pressure deficit is more important than temperature per se in causing decline in tree health', Ecology and Evolution, vol. 3, no. 8, pp. 2711-2729.
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Drought-induced tree mortality is occurring across all forested continents and is expected to increase worldwide during the coming century. Regional-scale forest die-off influences terrestrial albedo, carbon and water budgets, and land-surface energy partitioning. Although increased temperatures during drought are widely identified as a critical contributor to exacerbated tree mortality associated with global-change-type drought, corresponding changes in vapor pressure deficit (D) have rarely been considered explicitly and have not been disaggregated from that of temperature per se. Here, we apply a detailed mechanistic soilplantatmosphere model to examine the impacts of drought, increased air temperature (+2&deg;C or +5&deg;C), and increased vapor pressure deficit (D; +1 kPa or +2.5 kPa), singly and in combination, on net primary productivity (NPP) and transpiration and forest responses, especially soil moisture content, leaf water potential, and stomatal conductance. We show that increased D exerts a larger detrimental effect on transpiration and NPP, than increased temperature alone, with or without the imposition of a 3-month drought. Combined with drought, the effect of increased D on NPP was substantially larger than that of drought plus increased temperature. Thus, the number of days when NPP was zero across the 2-year simulation was 13 or 14 days in the control and increased temperature scenarios, but increased to approximately 200 days when D was increased. Drought alone increased the number of days of zero NPP to 88, but drought plus increased temperature did not increase the number of days. In contrast, drought and increased D resulted in the number of days when NPP = 0 increasing to 235 (+1 kPa) or 304 days (+2.5 kPa). We conclude that correct identification of the causes of global change-type mortality events requires explicit consideration of the influence of D as well as its interaction with drought and temperature
Cleverly, J.R., Boulain, N.P., Villalobos-Vega, R., Grant, N.M., Faux, R., Wood, C., Cook, P., Yu, Q., Leigh, A. & Eamus, D. 2013, 'Dynamics of component carbon fluxes in a semi-arid Acacia woodland, central Australia', Journal of Geophysical Research: Biogeosciences, vol. 118, no. 3, pp. 1168-1185.
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Vast areas in the interior of Australia are exposed to regular but infrequent periods of heavy rainfall, interspersed with long periods at high temperatures, but little is known of the carbon budget of these remote areas or how they respond to extreme precipitation. In this study, we applied three methods to partition net ecosystem photosynthesis into gross primary production (GPP) and ecosystem respiration (Re) during two years of contrasting rainfall. The first year was wet (>250 mm above average rainfall), while little precipitation fell during the second year (>100 mmbelow average). During the first year of study, rates of GPP were large (793 g C m_2 yr_1) in this semi-arid Mulga (Acacia aneura) and grass savanna due to complementary photosynthetic responses by the canopy and C4 understorey to cycles of heavy rainfall. Patterns in GPP during the summer and autumn matched those in leaf area index (LAI), photosynthetic activity, and autotrophic respiration. During the dry year, small but positive photosynthetic uptake by Mulga contributed to the neutral carbon budget (GPP / Re = 1.06 &plusmn; 0.03). Small rates of photosynthesis by evergreen Mulga when dry were supported by storage of soil moisture above a relatively shallow hardpan. Little soil organic matter (1.1%) was available to support heterotrophic respiration (Rh) without input of fresh substrate. The two largest sources of Re in this study were autotrophic respiration by the seasonal understorey and Rh through decomposition of fresh organic matter supplied by the senescent understorey.
Cleverly, J.R., Chen, C., Boulain, N.P., Villalobos-Vega, R., Faux, R., Grant, N.M., Yu, Q. & Eamus, D. 2013, 'Aerodynamic resistance and Penman-Monteith evapotranspiration over a seasonally two-layered canopy in semi-arid central Australia', Journal of Hydrometeorology, vol. 14, no. 1, pp. 1562-1570.
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Accurate prediction of evapotranspiration E depends upon representative characterization of meteoro- logical conditions in the boundary layer. Drag and bulk transfer coefficient schemes for estimating aero- dynamic resistance to vapor transfer were compared over a semiarid natural woodland ecosystem in central Australia. Aerodynamic resistance was overestimated from the drag coefficient, resulting in limited E at intermediate values of vapor pressure deficit. Large vertical humidity gradients were present during the summer, causing divergence between momentum and vapor transport within and above the canopy surface. Because of intermittency in growth of the summer-active, rain-dependent understory and physiological re- sponses of the canopy, leaf resistance varied from less than 50 sm21 to greater than 106 sm21, in which the particularly large values were obtained from inversion of drag coefficient resistance. Soil moisture limitations further contributed to divergence between actual and reference E. Unsurprisingly, inclusion of site-specific meteorological (e.g., vertical humidity gradients) and hydrological (e.g., soil moisture content) information improved the accuracy of predicting E when applying PenmanMonteith analysis. These results apply re- gardless of canopy layering (i.e., even when the understory was not present) wherever atmospheric humidity gradients develop and are thus not restricted to two-layer canopies in semiarid regions.
Breshears, D.D., Adams, H.D., Eamus, D., McDowell, N.G., Law, D.J., Will, R.E., Williams, A.P. & Zou, C.B. 2013, 'The critical amplifying role of increasing atmospheric moisture demand on tree mortality and associated regional die-off', Frontiers in Plant Science, vol. 4, no. 1, pp. 1-4.
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Drought-induced tree mortality, including large-scale die-off events and increases in background rates of mortality, is a global phenomenon (Allen et al., 2010) that can directly impact numerous earth system properties and ecosystem goods and services (Adams et al., 2010; Breshears et al., 2011; Anderegg et al., 2013). Tree mortality is particularly of concern because of the likelihood that it will increase in frequency and extent with climate change (McDowell et al., 2008, 2011; Adams et al., 2009; McDowell, 2011; Williams et al., 2013). Recent plant science advances related to drought have focused on understanding the physiological mechanisms that not only affect plant growth and associated carbon metabolism, but also the more challenging issue of predicting plant mortality thresholds (McDowell et al., 2013). Although some advances related to mechanisms of mortality have been made and have increased emphasis on interrelationships between carbon metabolism and plant hydraulics (McDowell et al., 2011), notably few studies have specifically evaluated effects of increasing atmospheric demand for moisture (i.e., vapour pressure deficit; VPD) on rates of tree death. In this opinion article we highlight the importance of considering the key risks of future large-scale tree die-off and other mortality events arising from increased VPD. Here we focus on mortality of trees, but our point about the importance of VPD is also relevant to other vascular plants.
Zhao, C., Liu, C., Zhao, J., Xia, J., Yu, Q. & Eamus, D. 2013, 'Zooplankton in highly regulated rivers: Changing with water environment', Ecological Engineering, vol. 58, no. 1, pp. 323-334.
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The Huai River Basin (HRB) of China is well-known globally for the extent of severe human activities (e.g., waste disposal and water project construction) which have resulted in severe water pollution and subsequently degraded water ecosystem quality in recent decades. However, influence of water pollution on water ecosystems has not yet been fully realized due to lack of water ecosystem data. In food webs of freshwater ecosystems, zooplankton occupy a critical position but they are highly susceptible to pollutants and temperature which in turn impact the community structure and biodiversity of zooplankton to a great extent. This paper aimed to assess impact of water chemistry variation on zooplankton through ecological-niche models and spatial heterogeneity of zooplankton along with water chemistry in the HRB. We investigated the impacts of nine dominant water chemistry indicators on zooplankton distribution and composition via ecological niche models based on water chemistry status and zooplankton communities at 71 typical sites of the HRB. A fuzzy clustering method (FCM) was employed to help study the impact characteristics and the spatial heterogeneity. Results indicate that across the nine water chemistry indicators, changes in water temperature has minimal impact on the zooplankton community of the Huai River while small variation in ammonianitrogen exerts significant stress on the community; with respect to water temperature and total phosphorous zooplankton species in the HRB are coexisting with little competition; as to spatial heterogeneity of zooplankton communities, communities in the southwest and southeast mountainous regions may adapt well to habitat variations, while those in the middle and northeast areas have a weak adaptability to habitat changes.
Zhao, C., Liu, C., Xia, J., Zhang, Y., Yu, Q. & Eamus, D. 2012, 'Recognition of key regions for restoration of phytoplankton communities in the Huai River basin, China', Journal Of Hydrology, vol. 420-421, pp. 292-300.
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Healthy phytoplankton communities are the basis of healthy water ecosystems, and form the foundation of many freshwater food webs. Globally many freshwater ecosystems are degraded because of intensive human activities, so water ecosystem restoration is a
Barton, C., Duursma, R.A., Medlyn, B.E., Ellsworth, D.S., Eamus, D., Tissue, D., Adams, M.A., Conroy, J.P., Crous, K.Y., Liberloo, M., Low, M., Linder, S. & McMurtrie, R.E. 2012, 'Effects of elevated atmospheric [CO2] on instantaneous transpiration efficiency at leaf and canopy scales in Eucalyptus saligna', Global Change Biology, vol. 18, no. 2, pp. 585-595.
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Rising atmospheric concentrations of CO2 (Ca) can reduce stomatal conductance and transpiration rate in trees, but the magnitude of this effect varies considerably among experiments. The theory of optimal stomatal behaviour predicts that the ratio of pho
Yunusa, I.A., Loganathan, L., Nissanka, S.P., Manoharan, V., Burchett, M., Skilbeck, G. & Eamus, D. 2012, 'Application of coal fly ash in agriculture: A strategic perspective', Critical Reviews in Environmental Science and Technology, vol. 42, no. 6, pp. 559-600.
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Fly ash is a major waste of coal-power generation and its management is a major environmental and economic challenge, and it will become even more critical with a projected increase in the reliance on coal for power generation. The authors discuss how th
Zhao, Z., Eamus, D., Yu, Q., Li, Y., Yang, H. & Li, J. 2012, 'Climate constraints on growth and recruitment patterns of Abies faxoniana over altitudinal gradients in the Wanglang Natural Reserve, eastern Tibetan Plateau', Australian Journal Of Botany, vol. 60, no. 7, pp. 602-614.
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The radial growth and recruitment patterns of trees in subalpine areas are subject to the influence of changing environmental conditions associated with changes in elevation. To investigate responses of fir radial growth and recruitment to climate factors at different elevations, tree-ring width chronologies and age structures of Abies faxoniana were developed from five sampling sites at ~28003300 m elevation on the north-western and south-eastern aspects in the Wanglang Natural Reserve on the eastern edge of Tibetan Plateau. Statistical characteristics of the chronologies indicated that expressed population signal and signal-to-noise ratio increased with increasing elevation in the north-western aspect; the reverse was observed on the south-eastern aspect. Correlation analysis between chronologies and climate variables showed that fir radial growth was negatively correlated with previous growing season mean temperatures and was positively correlated with January precipitation in all plots. The amount of precipitation in the growing season (June and July) greatly influenced radial growth in the two lower sites of both the aspects. The three plots on the north-western aspect were characterised by significant rates of tree recruitment in the past five decades.
Li, L., Wang, Y., Yu, Q., Pak, B., Eamus, D., Yan, J., van Gorsel, E. & Baker, I.T. 2012, 'Improving the responses of the Australian community land surface model (CABLE) to seasonal drought', Journal of Geophysical Research: Biogeosciences, vol. 117, p. G04002.
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Correct representations of root functioning, such as root water uptake and hydraulic redistribution, are critically important for modeling the responses of vegetation to droughts and seasonal changes in soil moisture content. However, these processes are poorly represented in global land surface models. In this study, we incorporated two root functions: a root water uptake function which assumes root water uptake efficiency varies with rooting depth, and a hydraulic redistribution function into a global land surface model, CABLE. The water uptake function developed by Lai and Katul (2000) was also compared with the default one (see Wang et al., 2010) that assumes that efficiency of water uptake per unit root length is constant. Using eddy flux measurements of CO2 and water vapor fluxes at three sites experiencing different patterns of seasonal changes in soil water content, we showed that the two root functions significantly improved the agreement between the simulated fluxes of net ecosystem exchange and latent heat flux and soil moisture dynamics with those observed during the dry season while having little impact on the model simulation during the wet seasons at all three sites. Sensitivity analysis showed that varying several model parameters influencing soil water dynamics in CABLE did not significantly affect the model's performance. We conclude that these root functions represent a valuable improvement for land surface modeling and should be implemented into CABLE and other land surface models for studying carbon and water dynamics where rainfall varies seasonally or interannually.
Yunusa, I.A., Zolfaghar, S., Zeppel, M.J., Li, Z., Palmer, A. & Eamus, D. 2012, 'Fine root biomass and its relationship to evapotranspiration in woody and grassy vegetation covers for ecological restoration of waste storage and mining landscapes', Ecosystems, vol. 15, no. 1, pp. 113-127.
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Production and distribution of fine roots (<= 2.0 mm diameter) are central to belowground ecological processes. This is especially true where vegetation serves as a pump to prevent saturation of soil and possible drainage of excess water into or from potentially toxic waste material stored underground or in mounds aboveground. In this study undertaken near Sydney in Australia, we determined fine root biomass and evapotranspiration (ET) on a waste disposal site restored with either a 15-year-old grass sward or plantations of mixed woody species that were either 5 years old (plantation-5) with a vigorous groundcover of pasture legumes and grasses, or 3 years old (plantation-3) with sparse groundcover. These sites were compared with nearby remnant woodland; all four were located within 0.5-km radius at the same site. Ranking of fine root biomass was in the order woodland (12.3 Mg ha(-1)) > plantation-5 (8.3 Mg ha(-1)) > grass (4.9 Mg ha(-1)) > plantation-3 (1.2 Mg ha(-1)) and was not correlated with nutrient contents in soil or plants, but reflected the form and age of the vegetation covers. Trends in root length density (RLD) and root area index (RAI) followed those in root biomass, but the differences in RAI were larger than those in biomass amongst the vegetation covers. Annual ET in the dry year of 2009 was similar in the three woody vegetation covers (652-683 mm) and was at least 15% larger than for the grass (555 mm), which experienced restrained growth in winter and periodic mowing. This resulted in drainage from the grass cover while there was no drainage from any of the woody vegetation covers.
Ali, M.M., Al-Ani, A., Eamus, D. & Tan, D.K. 2012, 'A New Image-Processing-Based Technique for Measuring Leaf Dimensions', American-Eurasian J. Agric. & Environ. Sci., vol. 12, no. 12, pp. 1588-1594.
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We propose in this paper a new method for measuring a number of leaf dimension parameters including height, width, average width, perimeter and area. A digital scanner is utilized to acquire leaf images, which unlike digital cameras, requires no calibration in terms of size and angle of the acquired images. Edge detection, filtering and thresholding algorithms are applied to identify the leaf section of the image against the background. Forty leaves that differ in shape and size were used to validate the estimated parameters against the true values and parameters produced by the popular Li-Cor 3100. Data indicated that the proposed method achieved a constantly high accuracy
Ali, M.M., Al-Ani, A., Eamus, D. & Tan, D.K. 2012, 'A New Image Processing Based Technique to Determine Chlorophyll in Plants', American-Eurasian J. Agric. & Environ. Sci., vol. 12, no. 10, pp. 1323-1328.
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Leaf colour is usually used as a guide for assessments of nutrient status and plant health. We propose a new inexpensive, hand-held and easy-to-use technique for the detection of chlorophyll content and foliar nitrogen content in plants based on leaf colour. This method provides a rapid analysis and data storage at minimal cost and does not require any technical or laboratory skills. Most of the existing methods that examined relationships between chlorophyll status and leaf colour were developed for particular species. These methods acquire leaf images using digital cameras, which can be sensitive to lighting conditions (colour, angle, flux density) and hence, require proper calibration. Our method analyses leaf colour images obtained from a digital scanner that requires minimal calibration compared as it has its one light source and the angle and distance between light and leaf are constant. Our new algorithm produced superior correlations with the true value of foliar chlorophyll content measured in the laboratory compared with existing non-destructive methods when applied to three different species (lettuce, broccoli and tomato).
Medlyn, B.E., Duursma, R.A., Eamus, D., Ellsworth, D.S., Prentice, I.C., Barton, C.V.M., Crous, K.Y., De Angelis, P., Freeman, M. & Wingate, L. 2012, 'Reconciling the optimal and empirical approaches to modelling stomatal conductance (vol 17, pg 2134, 2011)', GLOBAL CHANGE BIOLOGY, vol. 18, no. 11, pp. 3476-3476.
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Medlyn, B.E., Duursma, R., Eamus, D., Ellsworth, D.S., Prentice, I., Barton, C., Crous, K., De Angelis, P., Freeman, M. & Wingate, L. 2011, 'Reconciling the optimal and empirical approaches to modelling stomatal conductance', Global Change Biology, vol. 17, no. 6, pp. 2134-2144.
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Models of vegetation function are widely used to predict the effects of climate change on carbon, water and nutrient cycles of terrestrial ecosystems, and their feedbacks to climate. Stomatal conductance, the process that governs plant water use and carbon uptake, is fundamental to such models
Yunusa, I.A., Fuentes, S., Palmer, A., Macinnis-Ng, C.M., Zeppel, M.J. & Eamus, D. 2011, 'Latent Heat Fluxes During Two Contrasting Years From A Juvenile Plantation Established Over A Waste Disposal Landscape', Journal Of Hydrology, vol. 399, no. 1-2, pp. 48-56.
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Revegetation to restore hydrological function to highly disturbed landscapes used for waste disposal or mining is often constrained by the initial low rates of water-use during the early phases of the developing vegetation. This problem is especially pronounced for revegetation that relies on trees due to their prolonged lead-time to achieve canopy closure. Initial low rates of water-use can however be overcome if a groundcover of quick-growing herbaceous species is planted first. To demonstrate the significance of groundcover in the early phase of revegetation, we undertook an energy balance analysis using the Bowen ratio technique for a juvenile plantation growing over a heavy groundcover of herbaceous species on a waste disposal site in 2006/2007 and 2007/2008. Latent heat flux (kE) from the landscape (trees plus groundcover and soil) fluctuated widely between 0.5 and 22 MJ m2 d1 and accounted for between 60% and 90% of available energy at the site; this percentage exceeded 100% during periods with significant advection.
Macinnis-Ng, C.M., Zeppel, M.J., Williams, M. & Eamus, D. 2011, 'Applying a SPA model to examine the impact of climate change on GPP of open woodlands and the potential for woody thickening', Ecohydrology, vol. 4, no. 3, pp. 379-393.
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Woody thickening is a global phenomenon that influences landscape C density, regional ecohydrology and biogeochemical cycling. The aim of the work described here is to test the hypothesis that increased atmospheric CO2 concentration, with or without photosynthetic acclimation, can increase gross primary production (GPP) and that this can explain woody thickening. We examine mechanisms underlying the response of GPP and highlight the importance of changes in soil water content by applying a detailed soil-plant-atmosphere model. Through this model, we show that CO2 enrichment with decreased or increased D and photosynthetic acclimation results in decreased canopy water use because of reduced gs. The decline in water use coupled with increased photosynthesis resulted in increased GPP, water-use efficiency and soil moisture content. This study shows that this is a valid mechanism for GPP increase because of CO2 enrichment coupled with either a decrease or an increase in D, in water-limited environments. We also show that a large increase in leaf area index could be sustained in the future as a result of the increased soil moisture content arising from CO2 enrichment and this increase was larger if D decreases rather than increases in the future. Large-scale predictions arising from this simple conceptual model are discussed and found to be supported in the literature. We conclude that woody thickening in Australia and probably globally can be explained by the changes in landscape GPP and soil moisture balance arising principally from the increased atmospheric CO2 concentration.
Yunusa, I.A., Manoharan, V., Odeh, I., Shrestha, S., Skilbeck, G. & Eamus, D. 2011, 'Structural And Hydrological Alterations Of Soil Due To Addition Of Coal Fly Ash', Journal of Soils Sediments, vol. 11, no. 3, pp. 423-431.
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We tested the potential of using coal fly ash for improving the physical and hydrological characteristics of coarse and medium-textured agricultural soils. Acidic (FWA) and alkaline (FNSW) fly ashes were used to amend a range of representative agricultural soils. In the first experiment, fly ash was applied to the top 10 cm of 1-m long intact cores of a sandy loam soil at rates of 0, 12, 36 or 108 Mg/ha and sown with canola; after harvest, bulk density (BD), aggregate stability and mean weight diameter (MWD) were measured on the soil. In the second experiment, we assessed water retention at field capacity (-300 kPa) and permanent wilting point (-1,500 kPa) for sandy and loamy soils amended with FNSW at 0.0-16% (w/w). The third experiment used rainfall simulation to assess erodibility of sandy and loamy soils mixed with FNSW at rates of 0, 5 or 20 Mg/ha.
Whitley, R.J., Macinnis-Ng, C.M., Hutley, L.B., Beringer, J., Zeppel, M.J., Williams, M., Taylor, D.T. & Eamus, D. 2011, 'Is productivity of mesic savannas light limited or water limited? Results of a simulation study', Global Change Biology, vol. 17, no. 10, pp. 3130-3149.
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A soil-plant-atmosphere model was used to estimate gross primary productivity (GPP) and evapotranspiration (ET) of a tropical savanna in Australia. This paper describes model modifications required to simulate the substantial C4 grass understory together with C3 trees. The model was further improved to include a seasonal distribution of leaf area and foliar nitrogen through 10 canopy layers. Model outputs were compared with a 5-year eddy covariance dataset. Adding the C4 photosynthesis component improved the model efficiency and root-mean-squared error (RMSE) for total ecosystem GPP by better emulating annual peaks and troughs in GPP across wet and dry seasons. The C4 photosynthesis component had minimal impact on modelled values of ET. Outputs of GPP from the modified model agreed well with measured values, explaining between 79% and 90% of the variance and having a low RMSE (0.003-0.281 g C m(-2) day(-1)). Approximately, 40% of total annual GPP was contributed by C4 grasses. Total (trees and grasses) wet season GPP was approximately 75-80% of total annual GPP. Light-use efficiency (LUE) was largest for the wet season and smallest in the dry season and C4 LUE was larger than that of the trees. A sensitivity analysis of GPP revealed that daily GPP was most sensitive to changes in leaf area index (LAI) and foliar nitrogen (N-f) and relatively insensitive to changes in maximum carboxylation rate (V-cmax), maximum electron transport rate (J(max)) and minimum leaf water potential (Psi(min)). The modified model was also able to represent daily and seasonal patterns in ET, (explaining 68-81% of variance) with a low RMSE (0.038-0.19 mm day(-1)). Current values of N-f, LAI and other parameters appear to be colimiting for maximizing GPP. By manipulating LAI and soil moisture content inputs, we show that modelled GPP is limited by light interception rather than water availability at this site.
Zeppel, M.J., Lewis, J.D., Medlyn, B.E., Barton, C., Duursma, R., Eamus, D., Adams, M.A., Phillips, N., Elsworth, D.S., Forster, M.A. & Tissue, D. 2011, 'Interactive effects of elevated CO2 and drought on nocturnal water fluxes in Eucalyptus saligna', Tree Physiology, vol. 31, no. 9, pp. 932-944.
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Nocturnal water flux has been observed in trees under a variety of environmental conditions and can be a significant contributor to diel canopy water flux. Elevated atmospheric CO 2 (elevated [CO 2]) can have an important effect on day-time plant water fluxes, but it is not known whether it also affects nocturnal water fluxes. We examined the effects of elevated [CO 2] on nocturnal water flux of field-grown Eucalyptus saligna trees using sap flux through the tree stem expressed on a sapwood area (J s) and leaf area (E t) basis. After 19 months growth under well-watered conditions, drought was imposed by withholding water for 5 months in the summer, ending with a rain event that restored soil moisture. Reductions in J s and E t were observed during the severe drought period in the dry treatment under elevated [CO 2], but not during moderate- and post-drought periods. Elevated [CO 2] affected night-time sap flux density which included the stem recharge period, called 'total night flux' (19:00 to 05:00, J s,r), but not during the post-recharge period, which primarily consisted of canopy transpiration (23:00 to 05:00, J s,c). Elevated [CO 2] wet (EW) trees exhibited higher J s,r than ambient [CO 2] wet trees (AW) indicating greater water flux in elevated [CO 2] under well-watered conditions. However, under drought conditions, elevated [CO 2] dry (ED) trees exhibited significantly lower J s,r than ambient [CO 2] dry trees (AD), indicating less water flux during stem recharge under elevated [CO 2]. J s,c did not differ between ambient and elevated [CO 2]. Vapour pressure deficit (D) was clearly the major influence on night-time sap flux. D was positively correlated with J s,r and had its greatest impact on J s,r at high D in ambient [CO 2]. Our results suggest that elevated [CO 2] may reduce night-time water flux in E. saligna when soil water content is low and D is high. While elevated [CO 2] affected J s,r, it did not affect day-time water flux in wet soil, suggestin...
Barton, C., Duursma, R., Medlyn, B.E., Ellsworth, D.S., Eamus, D., Tissue, D., Adams, M.A., Conroy, J.P., Crous, K., Liberloo, M., Low, M., Linder, S. & McMurtrie, R.E. 2011, 'Effects of elevated atmospheric (CO2) on instantaneous transpiration efficiency at leaf and canopy scales in Eucalyptus saligna', Global Change Biology, vol. 17.
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Rising atmospheric concentrations of CO2 (Ca) can reduce stomatal conductance and transpiration rate in trees, but the magnitude of this effect varies considerably among experiments. The theory of optimal stomatal behaviour predicts that the ratio of photosynthesis to transpiration (instantaneous transpiration efficiency, ITE) should increase in proportion to Ca. We hypothesized that plants regulate stomatal conductance optimally in response to rising Ca. We tested this hypothesis with data from young Eucalyptus saligna Sm. trees grown in 12 climate-controlled whole-tree chambers for 2 years at ambient and elevated Ca. Elevated Ca was ambient + 240 ppm, 60% higher than ambient Ca. Leaf-scale gas exchange was measured throughout the second year of the study and leaf-scale ITE increased by 60% under elevated Ca, as predicted. Values of leaf-scale ITE depended strongly on vapour pressure deficit (D) in both CO2 treatments. Whole-canopy CO2 and H2O fluxes were also monitored continuously for each chamber throughout the second year. There were small differences in D between Ca treatments, which had important effects on values of canopy-scale ITE. However, when Ca treatments were compared at the same D, canopy-scale ITE was consistently increased by 60%, again as predicted. Importantly, leaf and canopy-scale ITE were not significantly different, indicating that ITE was not scale-dependent. Observed changes in transpiration rate could be explained on the basis that ITE increased in proportion to Ca. The effect of elevated Ca on photosynthesis increased with rising D. At high D, Ca had a large effect on photosynthesis and a small effect on transpiration rate. At low D, in contrast, there was a small effect of Ca on photosynthesis, but a much larger effect on transpiration rate. If shown to be a general response, the proportionality of ITE with Ca will allow us to predict the effects of Ca on transpiration rate.
Duursma, R.A., Barton, C., Eamus, D., Medlyn, B.E., Ellsworth, D.S., Forster, M.A., Tissue, D., Linder, S. & McMurtrie, R.E. 2011, 'Rooting depth explains [CO2] x drought interaction in Eucalyptus saligna', Tree Physiology, vol. 31, no. 9 Special Issue, pp. 922-931.
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Elevated atmospheric [CO2] (eC(a)) often decreases stomatal conductance, which may delay the start of drought, as well as alleviate the effect of dry soil on plant water use and carbon uptake. We studied the interaction between drought and eC(a) in a whole-tree chamber experiment with Eucalyptus saligna. Trees were grown for 18 months in their C-a treatments before a 4-month dry-down. Trees grown in eC(a) were smaller than those grown in ambient C-a (aC(a)) due to an early growth setback that was maintained throughout the duration of the experiment. Pre-dawn leaf water potentials were not different between C-a treatments, but were lower in the drought treatment than the irrigated control. Counter to expectations, the drought treatment caused a larger reduction in canopy-average transpiration rates for trees in the eC(a) treatment compared with aC(a). Total tree transpiration over the dry-down was positively correlated with the decrease in soil water storage, measured in the top 1.5 m, over the drying cycle; however, we could not close the water budget especially for the larger trees, suggesting soil water uptake below 1.5 m depth. Using neutron probe soil water measurements, we estimated fractional water uptake to a depth of 4.5 m and found that larger trees were able to extract more water from deep soil layers. These results highlight the interaction between rooting depth and response of tree water use to drought. The responses of tree water use to eC(a) involve interactions between tree size, root distribution and soil moisture availability that may override the expected direct effects of eC(a). It is essential that these interactions be considered when interpreting experimental results.
Whitley, R.J., Macinnis-Ng, C.M.O., Hutley, L.B., Beringer, J., Zeppel, M., Williams, M., Taylor, D. & Eamus, D. 2011, 'Is productivity of mesic savannas light limited or water limited? Results of a simulation study', Global Change Biology, vol. 17, no. 10.
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A soil-plant-atmosphere model was used to estimate gross primary productivity (GPP) and evapotranspiration (ET) of a tropical savanna in Australia. This paper describes model modifications required to simulate the substantial C4 grass understory together with C3 trees. The model was further improved to include a seasonal distribution of leaf area and foliar nitrogen through 10 canopy layers. Model outputs were compared with a 5-year eddy covariance dataset. Adding the C4 photosynthesis component improved the model efficiency and root-mean-squared error (RMSE) for total ecosystem GPP by better emulating annual peaks and troughs in GPP across wet and dry seasons. The C4 photosynthesis component had minimal impact on modelled values of ET. Outputs of GPP from the modified model agreed well with measured values, explaining between 79% and 90% of the variance and having a low RMSE (0.003-0.281gCm-2day-1). Approximately, 40% of total annual GPP was contributed by C4 grasses. Total (trees and grasses) wet season GPP was approximately 75-80% of total annual GPP. Light-use efficiency (LUE) was largest for the wet season and smallest in the dry season and C4 LUE was larger than that of the trees. A sensitivity analysis of GPP revealed that daily GPP was most sensitive to changes in leaf area index (LAI) and foliar nitrogen (Nf) and relatively insensitive to changes in maximum carboxylation rate (Vcmax), maximum electron transport rate (Jmax) and minimum leaf water potential (min). The modified model was also able to represent daily and seasonal patterns in ET, (explaining 68-81% of variance) with a low RMSE (0.038-0.19mmday-1). Current values of Nf, LAI and other parameters appear to be colimiting for maximizing GPP. By manipulating LAI and soil moisture content inputs, we show that modelled GPP is limited by light interception rather than water availability at this site. &copy; 2011 Blackwell Publishing Ltd.
Veeragathipillai, M., Yunusa, I.A., Loganathan, L., Lawrie, R., Skilbeck, G., Burchett, M., Murray, B. & Eamus, D. 2010, 'Assessments of Class F fly ashes for amelioration of soil acidity and their influence on growth and uptake of Mo and Se by canola', Fuel, vol. 89, no. 11, pp. 3498-3504.
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Coal fly ash can be used to ameliorate productivity constraints in agricultural soils, but their efficacy still remains highly variable. To ascertain the capacity of Class F fly ashes to modify pH of acidic soils, and their effects on the yield and uptake of molybdenum (Mo) and selenium (Se) by canola (Brassica napus L.), we applied two acidic and two alkaline Class F ashes at rates equivalent to 0, 12, 36, and 108 Mg/ ha to the top layer (0&acirc;10 cm) of 100 cm long intact cores of acidic sandy clay and clay loam soils. Only the alkaline ash which had the highest calcium carbonate equivalent (2.43%) increased the pH of the top 10 cm of the sandy clay soil. However, this ash was also highly saline and when applied at P36 Mg/ha it increased the electrical conductivity in the top soil layer. Increases in soil pH as a result of alkaline ash addition also elevated concentrations of Se in the plant shoot. The ashes with high concentrations of Mo and Se generally increased uptake of these elements in the plant shoot and/or seed. When these ashes were applied at 108 Mg/ha they increased the concentrations of these elements in the treated topsoil.
Veeragathipillai, M., Yunusa, I.A., Loganathan, L., Lawrie, R., Murray, B., Skilbeck, G. & Eamus, D. 2010, 'Boron contents and solubility in Australian fly ashes and its uptake by canola (Brassica napus L.) from the ash-amended soils', Australian Journal of Soil Research, vol. 48, no. 5, pp. 480-487.
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Phytotoxicity due to excessive boron (B) uptake by plants impedes routine agronomic utilisation of coal fly ash. We assessed 11 fly ashes (pH 3.14&acirc;10.77) having total B content (Bt) of 12&acirc;136 mg/kg, of which 20&acirc;30% was hot water soluble (Bs) in the acidic ashes (pH <5) and 5&acirc;10% in the alkaline ashes, for their potential to supply B to plants and their risk associated with phytotoxicity. We found the Bs/Bt to be negatively correlated (R2 = 0.63**, N = 11) with ash pH. We conducted two trials in which canola was grown in soils amended with fly ash. In the first trial, an alkaline fly ash (Bt 66 mg/kg) was incorporated at 5 rates of up to 625 Mg/ha into the top 50mm of 2 acidic soils in 0.30-m-long intact cores, and sown with canola. Boron concentration in leaves at flowering reached the phytotoxic threshold, and both plant growth and seed yield were reduced, only at 625 Mg/ha. In the second trial, 4 fly ashes (pH 3.29&acirc;10.77, Bt 12&acirc;127 mg/kg) were incorporated at 4 rates of up to 108 Mg/ha into the top 0.10mof 2 acidic soils in 1.0-m-long intact cores and then sown with canola. Ashes with highest Bt, when applied at 108 Mg/ha, increased B concentration in the topsoil only. Of the 2 ashes with the highest Bt, only that which produced low soil pH and applied at 108 Mg/ha increased B concentration in the shoot, but was still below phytotoxic threshold. The results suggest that B derived from these ashes may not cause phytotoxicity and excessive soil B accumulation if the ashes are applied at modest rates (<36 Mg/ha) to the topsoil layers.
Yunusa, I.A., Aumann, C., Rab, M.A., Merrick, N.P., Fisher, P.R., Eberbach, P. & Eamus, D. 2010, 'Topographical And Seasonal Trends In Transpiration By Two Co-Occurring Eucalyptus Species During Two Contrasting Years In A Low Rainfall Environment', Agricultural and Forest Meteorology, vol. 150, no. 9, pp. 1234-1244.
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Understanding the strategies that confer resilience on natural woodlands in drought prone environments is important for the conservation of these and similar ecosystems. Our main aim in this 2-year study was to assess traits (sapwood area, sapwood densit
Zeppel, M.J., Tissue, D., Taylor, D.T., Macinnis-Ng, C.M. & Eamus, D. 2010, 'Rates Of Nocturnal Transpiration In Two Evergreen Temperate Woodland Species With Differing Water-Use Strategies', Tree Physiology, vol. 30, no. 8, pp. 988-1000.
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Nocturnal fluxes may be a significant factor in the annual water budget of forested ecosystems. Here, we assessed sap flow in two co-occurring evergreen species (Eucalyptus parramattensis and Angophora bakeri) in a temperate woodland for 2 years in order
Yunusa, I.A., Zeppel, M.J., Fuentes, S., Macinnis-Ng, C.M., Palmer, A. & Eamus, D. 2010, 'An Assessment Of The Water Budget For Contrasting Vegetation Covers Associated With Waste Management', Hydrological Processes, vol. 24, no. 9, pp. 1149-1158.
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Revegetation is critical to restoring hydrological function on waste disposal sites in order to minimize runoff and drainage and safeguard the water quality of the catchment. In this study, we determined the components of soil-water balance between late
Palmer, A., Fuentes, S., Taylor, D.T., Macinnis-Ng, C.M., Zeppel, M.J., Yunusa, I.A. & Eamus, D. 2010, 'Towards A Spatial Understanding Of Water Use Of Several Land-Cover Classes: An Examination Of Relationships Amongst Pre-Dawn Leaf Water Potential, Vegetation Water Use, Aridity And Modis Lai', Ecohydrology, vol. 3, no. 1, pp. 1-10.
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Leaf area index (LAI) is a key physical variable which controls the exchange of water and CO, between the earth and the atmosphere. Recent improvements in the quality of satellite-derived estimates of LAI, specifically the MODIS LAI product, have led to
Barton, C., Ellsworth, D.S., Medlyn, B.E., Duursma, R., Tissue, D., Adams, M., Eamus, D., Conroy, J.P., McMurtrie, R.E., Parsby, J. & Linder, S. 2010, 'Whole-Tree Chambers For Elevated Atmospheric Co2 Experimentation And Tree Scale Flux Measurements In South-Eastern Australia: The Hawkesbury Forest Experiment', Agricultural And Forest Meteorology, vol. 150, no. 7-8, pp. 941-951.
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Resolving ecophysiological processes in elevated atmospheric CO2 (C-a) at scales larger than single leaves poses significant challenges. Here, we describe a field-based experimental system designed to grow trees up to 9m tall in elevated C-a with the cap
Macinnis-Ng, C.M., Fuentes, S., O'Grady, A.P., Palmer, A., Taylor, D.T., Whitley, R.J., Yunusa, I.A., Zeppel, M.J. & Eamus, D. 2010, 'Root Biomass Distribution And Soil Properties Of An Open Woodland On A Duplex Soil', Plant And Soil, vol. 327, no. 1-2, pp. 377-388.
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Data on the distribution of root biomass are critical to understanding the ecophysiology of vegetation communities. This is particularly true when models are applied to describe ecohydrology and vegetation function. However, there is a paucity of such in
O'Grady, A.P., Cook, P., Eamus, D., Duguid, A., Wischusen, J., Fass, T. & Worldege, D. 2009, 'Convergence of tree water use within an arid-zone woodland', Oecologia, vol. 160, no. 4, pp. 643-655.
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We examined spatial and temporal patterns of tree water use and aspects of hydraulic architecture in four common tree species of central Australia-Corymbia opaca, Eucalyptus victrix, E. camaldulensis and Acacia aneura-to better understand processes that constrain water use in these environments. These four widely distributed species occupy contrasting niches within arid environments including woodlands, floodplains and riparian environments. Measurements of tree water use and leaf water potential were made at two sites with contrasting water table depths during a period of high soil water availability following summer rainfall and during a period of low soil water availability following 7 months of very little rainfall during 2007. There were significant differences in specific leaf area (SLA), sapwood area to leaf area ratios and sapwood density between species. Sapwood to leaf area ratio increased in all species from April to November indicating a decline in leaf area per unit sapwood area. Despite very little rainfall in the intervening period three species, C. opaca, E. victrix and E. camaldulensis maintained high leaf water potentials and tree water use during both periods. In contrast, leaf water potential and water use in the A. aneura were significantly reduced in November compared to April. Despite contrasting morphology and water use strategies, we observed considerable convergence in water use among the four species. Wood density in particular was strongly related to SLA, sapwood area to leaf area ratios and soil to leaf conductance, with all four species converging on a common relationship. Identifying convergence in hydraulic traits can potentially provide powerful tools for scaling physiological processes in natural ecosystems.
Whitley, R.J., Medlyn, B.E., Zeppel, M.J., Macinnis-Ng, C.M. & Eamus, D. 2009, 'Comparing the Penman-Monteith equation and a modified Jarvis-Stewart model with an artificial neural network to estimate stand-scale transpiration and canopy conductance', Journal Of Hydrology, vol. 373, no. 1-2, pp. 256-266.
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The responses of canopy conductance to variation in solar radiation, vapour pressure deficit and soil moisture have been extensively modelled using a Jarvis-Stewart (JS) model. Modelled canopy conductance has then often been used to predict transpiration using the Penman-Monteith (PM) model. We previously suggested an alternative approach in which the JS model is modified to directly estimate transpiration rather than canopy conductance. In the present study we used this alternative approach to model tree water fluxes from an Australian native forest over an annual cycle. For comparative purposes we also modelled canopy conductance and estimated transpiration via the PM model. Finally we applied an artificial neural network as a statistical benchmark to compare the performance of both models. Both the PM and modified JS models were parameterised using solar radiation, vapour pressure deficit and soil moisture as inputs with results that compare well with previous studies. Both models performed comparably well during the summer period. However, during winter the PM model was found to fail during periods of high rates of transpiration. In contrast, the modified JS model was able to replicate observed sapflow measurements throughout the year although it too tended to underestimate rates of transpiration in winter under conditions of high rates of transpiration. Both approaches to modelling transpiration gave good agreement with hourly, daily and total sums of sapflow measurements with the modified JS and PM models explaining 87% and 86% of the variance, respectively. We conclude that these three approaches have merit at different time-scales.
Yunusa, I.A., Burchett, M., Veeragathipillai, M., DeSilva, L., Eamus, D. & Skilbeck, G. 2009, 'Photosynthetic Pigment Concentrations, Gas Exchange and Vegetative Growth for Selected Monocots and Dicots Treated with Two Contrasting Coal Fly Ashes', Journal of Environmental Quality, vol. 38, no. 4, pp. 1466-1472.
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There is uncertainty as to the races of coal fly ash needed for optimum physiological processes and growth. In the current study we tested the hyothesis that photosynthetic pigments concentrations and CO2 assimilation (A) are more sensitive than dry weights in plants grown on media amended with coal fly ash. We applied the Terrestrial Plant Growth Test (Guideline 208) protocols of the Organization for Economic Cooperation and Development (OECD) to monocots [barley (Hordeum vulgare) and ryegrass (Secale cereale)] and dicots [canola (Brasica napus), radish (Raphanus sativus), field peas (Pisum sativum), and lucerne (Medicago sativa)] on media amended with fly ashes derived from semi-bituminous (gray ash) or lignite (red ash) coals at rates of 0, 2.5, 5.0, 10, or 20 Mg ha(-1). The red ash had higher elemental concentrations and salinity than the gray ash. Fly ash addition had no significant effect on germination by any of the six species. At moderate rates (<= 10 Mg ha(-1)) both ashes increased (P < 0.05) growth rates and concentrations of chlorophylls a and b, but reduced carotenoid concentrations. Addition of either ash increased A in radish and transpiration in barley Growth rates and final dry weights were reduced for all of the six test species when addition rates exceeded 10 Mg ha(-1) for gray ash and 5 Mg ha(-1) for red ash. We concluded that plant dry weights, rather than pigment concentrations and/or instantaneous rates of photosynthesis, are more consistent for assessing subsequent growth in plants Supplied with fly ash. Copyright (C) 2009 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher.
Zeppel, M., Macinnis-Ng, C., Palmer, A., Taylor, D., Whitley, R., Fuentes, S., Yunusa, I., Williams, M. & Eamus, D. 2009, 'An analysis of the sensitivity of sap flux to soil and plant variables assessed for an Australian woodland using a soil-plant-atmosphere model (vol 35, pg 509, 2008)', FUNCTIONAL PLANT BIOLOGY, vol. 36, no. 12, pp. 1120-U108.
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Zeppel, M.J. & Eamus, D. 2008, 'Co-ordination of leaf area, sapwood area and canopy conductance leads to species convergence of tree water use in a remnant evergreen woodland.', Australian Journal Of Botany, vol. 36, no. 2, pp. 97-108.
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This paper compares rates of tree water use, Huber value, canopy conductance and canopy decoupling of two disparate, co-occurring tree species, in a stand of remnant native vegetation in temperate Australia in order to compare their relative behaviour seasonally and during and after a drought. The study site was an open woodland dominated by Eucalyptus crebra F.Muell. (a broad-leaved species) and Callitris glaucophylla J.Thompson & L.A.S. Johnson (a needle-leaved tree species). Tree water use was measured with sapflow sensors and leaf area and sapwood area were measured destructively on felled trees. The Huber value was calculated as the ratio of sapwood area to leaf area. Diameter at breast height (DBH) of the stem was used as a measure of tree size. Canopy conductance was calculated with an inversion of the PenmanMonteith equation, whereas canopy decoupling) was calculated as described by Lu et al. (2003). The relationship between DBH and daily total water use varied during the four measurement periods, with largest rates of water use observed in summer 20032004, following a large rainfall event and the smallest maximum water use observed in winter 2003 when monthly rainfall was much less than the long-term mean for those months. Despite differences in the relationship between sapwood area and DBH for the two species, the relationship between daily total water use and DBH did not differ between species at any time. The same rates of water use for the two species across sampling periods arose through different mechanisms; the eucalypt underwent significant changes in leaf area whereas the Callitris displayed large changes in canopy conductance, such that tree water use remained the same for both species during the 2-year period.
Whitley, R.J., Zeppel, M.J., Armstrong, N.G., Macinnis-Ng, C.M., Yunusa, I.A. & Eamus, D. 2008, 'A modified Jarvis-Stewart model for predicting stand-scale transpiration of an Australian native forest', Plant and Soil, vol. 305, no. 1-2, pp. 35-47.
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Rates of water uptake by individual trees in a native Australian forest were measured on the Liverpool Plains, New South Wales, Australia, using sapflow sensors. These rates were up-scaled to stand transpiration rate (expressed per unit ground area) using sapwood area as the scalar, and these estimates were compared with modelled stand transpiration. A modified Jarvis-Stewart modelling approach (Jarvis 1976), previously used to calculate canopy conductance, was used to calculate stand transpiration rate. Three environmental variables, namely solar radiation, vapour pressure deficit and soil moisture content, plus leaf area index, were used to calculate stand transpiration, using measured rates of tree water use to parameterise the model. Functional forms for the model were derived by use of a weighted non-linear least squares fitting procedure. The model was able to give comparable estimates of stand transpiration to those derived from a second set of sapflow measurements. It is suggested that short-term, intensive field campaigns where sapflow, weather and soil water content variables are measured could be used to estimate annual patterns of stand transpiration using daily variation in these three environmental variables. Such a methodology will find application in the forestry, mining and water resource management industries where long-term intensive data sets are frequently unavailable.
Zeppel, M.J., Macinnis-Ng, C.M., Ford, C.R. & Eamus, D. 2008, 'The response of sap flow to pulses of rain in a temperate Australian woodland', Plant and Soil, vol. 305, no. 1-2, pp. 121-130.
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In water-limited systems, pulses of rainfall can trigger a cascade of plant physiological responses. However, the timing and size of the physiological response can vary depending on plant and environmental characteristics, such as rooting depth, plant size, rainfall amount, or antecedent soil moisture. We investigated the influence of pulses of rainfall on the response of sap flow of two dominant evergreen tree species, Eucalyptus crebra (a broadleaf) and Callitris glaucophylla (a needle leaved tree), in a remnant open woodland in eastern Australia. Sap flow data were collected using heat-pulse sensors installed in six trees of each species over a 2 year period which encompassed the tail-end of a widespread drought. Our objectives were to estimate the magnitude that a rainfall pulse had to exceed to increase tree water use (i.e., define the threshold response), and to determine how tree and environmental factors influenced the increase in tree water use following a rainfall pulse. We used data filtering techniques to isolate rainfall pulses, and analysed the resulting data with multivariate statistical analysis. We found that rainfall pulses less than 20 mm did not significantly increase tree water use (P>0.05). Using partial regression analysis to hold all other variables constant, we determined that the size of the rain event (P<0.05, R 2=0.59), antecedent soil moisture (P<0.05, R 2=0.29), and tree size (DBH, cm, P<0.05, R 2=0.15), all significantly affected the response to rainfall. Our results suggest that the conceptual Threshold-Delay model describing physiological responses to rainfall pulses could be modified to include these factors. We further conclude that modelling of stand water use over an annual cycle could be improved by incorporating the T-D behaviour of tree transpiration.
Zeppel, M.J., Macinnis-Ng, C.M., Palmer, A., Taylor, D.T., Whitley, R.J., Fuentes, S., Yunusa, I.A., Williams, M. & Eamus, D. 2008, 'An analysis of the sensitivity of sap flux to soil and plant variables assessed for an Australian woodland using a soil-plant-atmosphere model', Functional Plant Biology, vol. 35, no. 6, pp. 509-520.
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Daily and seasonal patterns of tree water use were measured for the two dominant tree species, Angophora bakeri E.C.Hall (narrow-leaved apple) and Eucalyptus sclerophylla (Blakely) L.A.S. Johnson & Blaxell (scribbly gum), in a temperate, open, evergreen woodland using sap flow sensors, along with information about soil, leaf, tree and micro-climatological variables. The aims of this work were to: (a) validate a soilplantatmosphere (SPA) model for the specific site; (b) determine the total depth from which water uptake must occur to achieve the observed rates of tree sap flow; (c) examine whether the water content of the upper soil profile was a significant determinant of daily rates of sap flow; and (d) examine the sensitivity of sap flow to several biotic factors. It was found that: (a) the SPA model was able to accurately replicate the hourly, daily and seasonal patterns of sap flow; (b) water uptake must have occurred from depths of up to 3 m; (c) sap flow was independent of the water content of the top 80 cm of the soil profile; and (d) sap flow was very sensitive to the leaf area of the stand, whole tree hydraulic conductance and the critical water potential of the leaves, but insensitive to stem capacitance and increases in root biomass. These results are important to future studies of the regulation of vegetation water use, landscape-scale behaviour of vegetation, and to water resource managers, because they allow testing of large-scale management options without the need for large-scale manipulations of vegetation cover.
Eamus, D., Taylor, D.T., Macinnis-Ng, C.M., Shanahan, S. & De Silva, D.L. 2008, 'Comparing model predictions and experimental data for the reponse of stomatal conductance and guard cell turgor to manipulations of cuticular conductance, leaf-to-air vapour pressure difference and temperature: feedback mechanisms are able to account', Plant, Cell and Environment, vol. 31, no. 3, pp. 269-277.
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Stomata respond to increasing leaf-to-air vapour pressure difference (LAVPD) ( D) by closing. The mechanism by which this occurs is debated. A role for feedback and peristomatal transpiration has been proposed. In this paper, we apply a recent mechanistic model of stomatal behaviour, and compare model and experimental data for the influence of increasing D on stomatal conductance. We manipulated cuticular conductance ( g<sub>c</sub>) by three independent methods. First, we increased g<sub>c</sub> by using a solvent mixture applied to both leaf surfaces prior to determining stomatal responses to D; second, we increased g<sub>c</sub> by increasing leaf temperature at constant D; and third, we coated a small area of leaf with a light oil to decrease g<sub>c</sub>. In all three experiments, experimental data and model outputs showed very close agreement. We conclude, from the close agreement between model and experimental data and the fact that manipulations of g<sub>c</sub>, and hence cuticular transpiration, influenced g<sub>s</sub> in ways consistent with a feedback mechanism, that feedback is central in determining stomatal responses to D
Palmer, A., Fuentes, S., Taylor, D.T., Macinnis-Ng, C.M., Zeppel, M.J., Yunusa, I.A., February, E. & Eamus, D. 2008, 'The use of pre-dawn leaf water potential and MODIS LAI to explore seasonal trends in the phenology of Australian and southern African woodlands and savannas', Australian Journal Of Botany, vol. 56, no. 7, pp. 557-563.
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Trends in global soil moisture are needed to inform models of soilplantatmosphere interactions. Predawn leaf water potential (?pd), a surrogate for soil moisture and an index of plant water stress, has been routinely collected in Australian forests, woodlands and savannas, but the associated leaf area index (LAI) has seldom been available to enable the preparation of a ?pd on LAI relationship. Following an analysis of ?pd and MODIS LAI data from Australian forests, woodlands and savannas, we identified patterns in ?pd which provide an understanding of the role of soil-moisture status in controlling LAI. In the savanna of northern Australia, the MODIS LAI product had a basal value of 0.96 during the dry season as compared with a mean value of 2.5 for the wet season. The dry season value is equivalent to the LAI of the tree component and corresponds with ground-truthed LAI. ?pd is lowest (more negative) during the height of the dry season (late October) at -2.5 MPa, and highest (-0.1 MPa) during the wet season (early March). We present two models which predict ?pd from the MODIS LAI product. These may be useful surrogates for studying trends in soil moisture in highly seasonal climates and may contribute to climate change research.
Leal, S., Eamus, D., Grabner, M., Wimmer, R. & Cherubini, P. 2008, 'Tree rings of Pinus nigra from the Vienna basin region (Austria) show evidence of change in climatic sensitivity in the late 20th century', Canadian Journal Of Forest Research-Revue Canadienne De Recherche Forestiere, vol. 38, no. 4, pp. 744-759.
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The width of tree rings of Pinus nigra Arn. trees growing near the ecological limits for the species, in the Vienna basin, Austria, showed a strong and positive correlation with spring-summer precipitation, indicating a dependence of growth on water avai
Grigg, A., MacFarlane, C., Evangelista, C., Eamus, D. & Adams, M. 2008, 'Does initial spacing influence crown and hydraulic architecture of Eucalyptus marginata?', Tree Physiology, vol. 28, no. 5, pp. 753-760.
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Long-term declines in rainfall in south-western Australia have resulted in increased interest in the hydraulic characteristics of jarrah (Eucalyptus marginata Donn ex Smith) forest established in the region's drinking water catchments on rehabilitated ba
Taylor, D.T. & Eamus, D. 2008, 'Coordinating leaf functional traits with branch hydraulic conductivity: resource substitution and implications for carbon gain', Tree Physiology, vol. 28, no. 8, pp. 1169-1177.
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We Studied relationships among branch hydraulic conductivity, xylem embolism, stomatal conductance (g(s)), foliar nitrogen (N) concentration and specific leaf area (SLA) of seven tree species growing at four temperate woodland sites spanning a 464-1350 m
Zeppel, M.J., Macinnis-Ng, C.M., Yunusa, I.A., Whitley, R.J. & Eamus, D. 2008, 'Long term trends of stand transpiration in a remnant forest during wet and dry years', Journal Of Hydrology, vol. 349, pp. 200-213.
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Daily and annual rates of stand transpiration in a drought year and a non-drought year are compared in order to understand the adaptive responses of a remnant woodland to drought and predict the effect of land use change. Two methods were used to estimat
Fuentes, S., Palmer, A., Taylor, D.T., Zeppel, M.J., Whitley, R.J. & Eamus, D. 2008, 'An automated procedure for estimating the leaf area index (LAI) of woodland ecosystems using digital imagery, MATLAB programming and its application to an examination of the relationship between remotely sensed and field measurements of LAI.', Functional Plant Biology, vol. 35, no. 9-10, pp. 1070-1079.
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Leaf area index (LAI) is one of the most important variables required for modelling growth and water use of forests. Functional-structural plant models use these models to represent physiological processes in 3-D tree representations. Accuracy of these models depends on accurate estimation of LAI at tree and stand scales for validation purposes. A recent method to estimate LAI from digital images (LAI(D)) uses digital image capture and gap fraction analysis (Macfarlane et al. 2007b) of upward-looking digital photographs to capture canopy LAI(D) (cover photography). After implementing this technique in Australian evergreen Eucalyptus woodland, we have improved the method of image analysis and replaced the time consuming manual technique with an automated procedure using a script written in MATLAB7.4 (LAI(M)). Furthermore, we used this method to compare MODIS LAI values with LAI(D) values for a range of woodlands in Australia to obtain LAI at the forest scale. Results showed that the MATLAB script developed was able to successfully automate gap analysis to obtain LAI(M). Good relationships were achieved when comparing averaged LAI(D) and LAI(M) (LAI(M) = 1.009-0.0066 LAI(D); R(2) = 0.90) and at the forest scale, MODIS LAI compared well with LAI(D) (MODIS LAI = 0.9591 LAI(D)-0.2371; R(2) = 0.89). This comparison improved when correcting LAI(D) with the clumping index to obtain effective LAI (MODIS LAI = 1.0296 LAI(e) + 0.3468; R(2) = 0.91). Furthermore, the script developed incorporates a function to connect directly a digital camera, or high resolution webcam, from a laptop to obtain cover photographs and LAI analysis in real time. The later is a novel feature which is not available on commercial LAI analysis softwares for cover photography. This script is available for interested researchers.
Yunusa, I.A., Nuberg, I., Fuentes, S., Lu, P. & Eamus, D. 2008, 'A simple field validation of daily transpiration derived from sapflow using a porometer and minimal meteorological data', Plant And Soil, vol. 305, no. 1-2, pp. 15-24.
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Heat-pulse techniques are routinely used to estimate transpiration from canopies of woody plants typically without any local calibration, mainly because of the difficulty of doing so in the field and, frequently, lack of detailed weather data. This is de
Yunusa, I.A., Veeragathipillai, M., DeSilva, L., Eamus, D., Murray, B. & Nissanka, S. 2008, 'Growth and elemental accumulation by canola on soil amended with coal fly ash', Journal Of Environmental Quality, vol. 37, no. 3, pp. 1263-1270.
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To explore the agronomic potential of an Australian coal fly ash, we conducted two glasshouse experiments in which we measured chlorophyll fluorescence, CO2 assimilation (A), transpiration, stomatal conductance, biomass accumulation, seed yield, and elem
Pepper, D., McMurtrie, R.E., Medlyn, B.E., Keith, H. & Eamus, D. 2008, 'Mechanisms linking plant productivity and water status for a temperate Eucalyptus forest flux site: analysis over wet and dry years with a simple model', Functional Plant Biology, vol. 35, no. 6, pp. 493-508.
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A simple process-based model was applied to a tall Eucalyptus forest site over consecutive wet and dry years to examine the importance of different mechanisms linking productivity and water availability. Measured soil moisture, gas flux (CO2, H2O) and me
Yunusa, I.A.M., Nuberg, I.K., Fuentes, S., Lu, P. & Eamus, D. 2008, 'A simple field validation of daily transpiration derived from sapflow using a porometer and minimal meteorological data (vol 305, pg 15, 2008)', PLANT AND SOIL, vol. 310, no. 1-2, pp. 269-269.
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Zeppel, M. & Eamus, D. 2008, 'Coordination of leaf area, sapwood area and canopy conductance leads to species convergence of tree water use in a remnant evergreen woodland', AUSTRALIAN JOURNAL OF BOTANY, vol. 56, no. 2, pp. 97-108.
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MacFarlane, C., Hoffman, M.J., Eamus, D., Kerp, N., Higginson, S., McMurtrie, R.E. & Adams, M. 2007, 'Estimation of leaf area index in eucalypt forest using digital photography', Agricultural And Forest Meteorology, vol. 143, no. 3-4, pp. 176-188.
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We tested whether leaf area index (L) in eucalypt vegetation could be accurately estimated from gap fraction measurements made using both fisheye and non-fisheye digital photography. We compared methods that measure the gap fraction at a single zenith angles. We applied these methods in an unthinned stand of the broadleaf tree species Ecualyptus marginata that had an intial L of 3. We removed one-third of the trees and reapplied the methods, and then removed another one-third of the trees and applied the methods a tjird time. L from the photographic methods was compared to L obtained from destrictive sampling and allometry. We found that L was accurately estimated from non-fisheye images taken at the zenith, providing thaty the total gap fraction was divided into large, between-crown gaps and smaller, within-crown gaps, prior to using the Beer-Lambert law to estimate L. This rapid and simpel method corrected for foliage clumping and provided estimates of crown porosity, crown cover, foliage cover and the foliage clumping index at the zenith, but required an assumption about the lgiht extenction coefficient at the zenith. Fisheye photography also provided good estimates of L bit only if the images were corrected for the gamma function of the digital camera, and the combined Chen-Chilar and Lang-Xiang method of correcting for foliage prjection coefficient was. Method of obtaining and analysising gap fraction and gap size distributions from fisheye photography need further improvement to separate the effects of foliage clumping and leaf angle distribution.
Jahansooz, M., Yunusa, I.A., Coventry, D., Palmer, A. & Eamus, D. 2007, 'Radiation- And Water-Use Associated With Growth And Yields Of Wheat And Chickpea In Sole And Mixed Crops', European Journal Of Agronomy, vol. 26, no. 3, pp. 275-282.
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A renewed interest in mixed cropping for its potential to boost yields through increased capture and use of solar radiation and soil-water by the component species. This led to the present study, in which we assessed the performance of wheat and chickpea
Kelley, G., O'Grady, A.P., Hutley, L.B. & Eamus, D. 2007, 'A comparison of tree water use in two contiguous vegetation communities of the seasonally dry tropics of northern Australia: the importance of site water budget to tree hydraulics', Australian Journal Of Botany, vol. 55, no. 7, pp. 700-708.
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Tree water use in two contiguous communities (eucalypt open-forest and Melaleuca paperbark forest) was measured in tropical Australia, over a 2-year period. The aims of the study were to (1) quantify daily and seasonal patterns of water use in each community, (2) compare patterns of water use among the communities and (3) compare relationships among tree size, sapwood area and water use within the two contrasting vegetation communities. Access to deep soil water stores and the effect of run-on from the eucalypt forest resulted in a relatively high pre-dawn water potential throughout the year, particularly for Melaleuca forest. There were no differences in daily rates of water use, expressed on a sapwood area (Q s) basis, between the two eucalypt species examined (Eucalyptus miniata Cunn. Ex Schauer and E. tetrodonta F.Muell) at any time in the eucalypt forest. For both the eucalypt and Melaleuca forests, there was less seasonal variation in water use expressed on a leaf area (Q l) basis than on a Q s basis, and neither year nor season were significant factors in Q l. In the mono-specific Melaleuca forest, Q s was not significantly different between years or seasons. Water use on a Q l basis was similarly not significantly different between years or seasons in the Melaleuca forest. Leaf area index (LAI) of the eucalypt forest was about half of that of the Melaleuca forest throughout the year but sapwood area per hectare was 33% larger in the eucalypt than the Melaleuca forest, despite the basal area of the Melaeuca forest being almost double that of the eucalypt forest.
MacFarlane, C., Arndt, S.K., Livesley, S., Edgar, A., White, D., Adams, M. & Eamus, D. 2007, 'Estimation of leaf area index in eucalypt forest with vertical foliage, using cover and fullframe fisheye photography', Forest Ecology And Management, vol. 242, no. 2-3, pp. 756-763.
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This study compared fullframe fisheye photography and cover photography with destructive leaf area index (L) estimation and the Licor LAI-2000 plant canopy analyser (PCA) in plantations of the vertical leaved species Eucalyptus globulus. Fullframe fisheye photography differs from circular fisheye photography in that the images have reduced field of view such that the zenithal range of 0-90 degrees extends to the corners of the rectangular image, roughly doubling image resolution compared to circular images. Cover images instead are obtained by pointing a 70mm equivalent focal length lens (in 35mm format) straight upwards. Measurements of cover and indirect estimates of plant area index (Lt) were made in 12 stands of 6-8 years old Eucalyptus glubulus. L was measured using destructive sampling and allometry in nine of these stands and ranged from 2.5 to 6.6. Both foliage cover and Lt from the PCA were well correlated with L from allometry, but fullframe fisheye photography provided poor estimates of L despite corrections fro foliage clumping. Sampling location had a significant effect on estimates of crown porosity, crown cover and zenithal clumping index from cover photography. The zenithal extinction coefficient (k), calculated from L, crown porosity and cover, ranged from 0.14 to 0.025 and appeared to decrease as L increased; hence, we were unable to obtain an unambiguous estimate of k for E. globulus stands. Nonetheless, the study showed that L can be estimated from foliage cover with similar certainty to that of the PCA. We conclude that the greatest challenge facing indirect estimation of L in forests using photographic methods is to separate the effects of foliage angle from those of foliage clumping.
Yunusa, I.A., Eamus, D., De Silva, D.L., Murray, B., Burchett, M., Skilbeck, G. & Heidrich, C. 2006, 'Fly-ash: An exploitable resource for management of Australian agricultural soils', Fuel, vol. 85, no. 16, pp. 2337-2344.
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Agricultural soils in Australia have inherent limitations of structural and nutritional nature that pose major constraints to crop productivity. These soils are still productive due to intensive management that involves routine treatments with lime and g
O'Grady, A.P., Eamus, D., Cook, P. & Lamontagne, S. 2006, 'Groundwater use by riparian vegetation in the wet-dry tropics of northern Australia', Australian Journal of Botany, vol. 54, pp. 145-154.
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Within Australian and globally there is considerable concern about the potential impacts of groundwater extraction on ecosystems dependent on groundwater. In this study we have combined heat pulse and isotopic techniques to assess groundwater use by riparian vegetation along the Daly River in the Northern Territory. The riparian forests of the Daly River exhibited considerable structural and floristic complexity. More than 40 tress species were recorded during vegetation surveys and these exhibited a range of leaf phonologies, implying complex patterns of water resource partitioning within the riparian forests. Water use was afunction of species and season, and stand water use varied between 1.8 and 4.1 mm day-1. In general, however, water use tended to be igher in the wet season than suring the dry season, reflecting the contribution to stand water use bu dr-season deciduous tree sepcies. There was a strong relationship between stand basal area and stabd water use in the wet season, but the strength of this relationship was lower inthe dry season. The amount of groundwater use, as determined by analysis of deuterium concentrations in xylem sap, was principally a function of position in the landscape. Trees at lower elevations, closer to the river, used more groundwater than trees higher on the levees. By using a combination of techniques we showed that riparian vegetation along the Daly River was highly groundwater dependent and that these water-use requirements need to be considered in regional management plans for groundwater.
O'Grady, A.P., Eamus, D., Cook, P. & Lamontagne, S. 2006, 'Comparative water use by the riparian trees Melaleuca argentea and Corymbia bella in the wet-dry tropics of northern Australia', Tree Physiology, vol. 26, no. 2, pp. 219-228.
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We examined sources of water and daily and seasonal water use patterns in two riparian tree species occupying contrasting niches within riparian zones throughout the wet-dry tropics of northern Australia: Corymbia bella Hill and Johnson is found along th
Eamus, D. & Froend, R. 2006, 'Groundwater-dependent ecosystems the where, what and why of GDEs', Australian Journal Of Botany, vol. 54, no. 2, pp. 91-96.
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Murray, B., Hose, G.C., Eamus, D. & Licari, D.D. 2006, 'Valuation of groundwater-dependent ecosystems: a functional methodology incorporating ecosystem services', Australian Journal Of Botany, vol. 54, no. 2, pp. 221-229.
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Groundwater-dependent ecosystems (GDEs) are ecosystems that must have access to groundwater to maintain their ecological structure and function. Rapidly expanding numbers of humans are placing increased demands on groundwater for consumption, industry an
Zeppel, M.J., Yunusa, I.A. & Eamus, D. 2006, 'Daily, seasonal and annual patterns of transpiration from a stand of remnant vegetation dominated by a coniferous Callitris species and a broad-leaved Eucalyptus species', Physiologia Plantarum, vol. 127, no. 3, pp. 413-422.
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Quantifying water use of native vegetation is an important contribution to understanding landscape ecohydrology. Few studies provide long-term (more than one growing season) estimates of water use and even fewer quantify interseasonal and interannual var
Eamus, D., Froend, R., Loomes, R., Hose, G.C. & Murray, B. 2006, 'A functional methodology for determining the groundwater regime needed to maintain the health of groundwater-dependent vegetation', Australian Journal Of Botany, vol. 54, no. 2, pp. 97-114.
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In the past, the phrase environmental allocations of water has most often been taken to mean allocation of water to rivers. However, it is now accepted that groundwater-dependent ecosystems are an important feature of Australian landscapes and require an
Chen, X., Hutley, L.B. & Eamus, D. 2005, 'Soil organic carbon content at a range of north Australian tropical savannas with contrasting site histories', Plant And Soil, vol. 268, no. 1, pp. 161-171.
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Soils play an important role in the global carbon cycle, and can be major source or sink of CO2 depending upon land use, vegetation type and soil management practices. Natural and human impact on soil carbon concentration and storage is poorly understood
Lamontagne, S., Cook, P., O'Grady, A.P. & Eamus, D. 2005, 'Groundwater use by vegetation in a tropical savanna riparian zone (Daly River, Australia)', Journal Of Hydrology, vol. 310, no. 1-4, pp. 280-293.
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Soil water matric potentials (Psi(m)) and the deuterium (delta(2)H) composition at natural abundance levels of xylem water, soil water, river water and groundwater were used to evaluate whether trees use groundwater during the dry season in the riparian
Yunusa, I.A., Lu, P., Eamus, D. & Walker, R.R. 2005, 'Matching irrigation to vine-water requirements: limitations of using sap-flow technology for scheduling irrigation', Acta Horticulturae, vol. 694, pp. 165-171.
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Mismatch between water applied during irrigation and that required by the crop for transpiration is a major cause of poor returns per unit water use and of land degradation. Advances in commercial sap-flow gauges should provide opportunities for improving water management in tree-horticulture, but this has not been widely explored. In this study we tested the capabilit of sap-flow guages to detect water stress and, hence a need for irrigation, by withholding water for two months from actively growing, mature grapevines. Withholding irrigation reduced soil-water content in the 1.8m soil-profile by almost 40% compared to where irrigation was maintianed, by the reduced soil-water resulted in only a small decrease in the transpirationdeduced from sap flow throughout the 2-month period. This was despite a 3-fold increase in stomatal resistance and a rise of 1.0 C in leaf temperature for the stressed compred to the continuously irrigated vines. Reasons for this response are not clear, but it is possible that the stressed vines accessed water either directly from the waterble or from its capillary fringe. Withdrawal of irrigation also did not result in yield for the stressed-vines. Other implications of these finding are explored including proposals on weighted crop factor to match irrigation with grape-vine water requirements.
Zeppel, M.J. & Eamus, D. 2005, 'Tree water use under conditions of drought.', vol. 17, pp. 8-11.
Prior, L.D., Bowman, D. & Eamus, D. 2005, 'Intra-specific variation in leaf attributes of four savanna tree species across a rainfall gradient in tropical Australia', Australian Journal Of Botany, vol. 53, no. 4, pp. 323-335.
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Leaf attributes of four savanna tree species were measured along a rainfall gradient (1650-950mm per annum) in the Australian monsoon tropics. As the mean annual rainfall decreased, leaf thickness increased for three of these four species. However, a cor
Eamus, D., Macinnis-Ng, C.M., Hose, G.C., Zeppel, M.J., Taylor, D.T. & Murray, B. 2005, 'Ecosystem services: an ecophysiological examination', Australian Journal Of Botany, vol. 53, no. 1, pp. 1-19.
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This review aims to discuss ecosystem services, provide illustrative case studies at catchment and local scales and present future research needs. This review discusses the following: ( 1) Ecosystem services (ES) are those goods and services that are pro
Chave, J., Andalo, C., Brown, S., Cairns, M.A., Chambers, J.Q., Eamus, D., Folster, H., Fromard, F., Puig, H., Higuchi, N., Nelson, B.W., Kira, T., Lescure, J., Ogawa, H., Yamakura, T. & Riera, B. 2005, 'Tree allometry and improved estimation of carbon stocks and balance in tropical forests', Oecologia, vol. 145, no. 1, pp. 87-99.
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Tropical forests hold large stored of carbonyet uncertainty remains regarding their quantitative contribution to the global carbon cycle. One approach to quantifying carbon biomass stores consists in inferrinng changes from long-term forsts inventory data ito an estimate of aboveground biomass (AGB). We provide a critical reassessment of the quality and the robustness of these models across tropical forest types, using a large dataset of 2,410 trees- 5cm diameter, directly harvested in 27 study sites across the tropics. Proportional relationships between aboveground biomass and the product of wood density, trunk corss-sectional area, and total height are constructed. We also develop aregression model involving wood density and stem diameter only. Our models were tested for secondary and old-growth forets, for dry, moist and wet forests, for lowland and motane forests, and for mangrove forets, Themost important repdicators of AGB of a tree were, in decreasing order of importance, its truck diameter wood specific gravity, total height, and forest type (dry, moist, or wet). Overestimates prevailed, giving a bias of 0.5-6.5% when errors were averaged across all stands. Our regression models can be used reliably to predict aboveground tree biomass across a broad range of tropical forests. Because they are based on an unprecedented dataset, these models should imporve the quality of tropical biomass estimates, and bring consensus about the contribution of the tropical forest biome and tropical deforestation to the global carbon cycle.
McPherson, S., Eamus, D. & Murray, B. 2004, 'Seasonal impacts on leaf attributes of several tree species growing in three diverse ecosystems of south-eastern Australia', Australian Journal Of Botany, vol. 52, pp. 293-301.
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Patterns of leaf attributes were examined for six woody species growing in a eucalypt woodland, a mangorve, or a heathland in coastal NSW, Australia, during winter and summer. It was found that the rate of assimilation per unit of dry mass (Amass) of the mangrove species was largest, woodland species exhibiting an intermedaite rate and heathland species the smallest values of Amass. Mean habitat Amass did not change from winter to summer in the woodland or mangrove species but increased significantly in the heathland species. Averag specific leaf area (SLA) was largest for the mangrove species and smallest for the heathland species, with woodland species showing intermediate values. SLA of all species within a habitat did not change from winter to summer.Mean foliar nitrogen content (Nmass of the mangrove species was highest, intermediate for woodland species and lowest for heathland species. NMass was significantly related to Amass in both summer and winter and the individual slopes for this relationship in the summer and winter differed. In contrast, a common slope waws fitted to the relationship between SLA and Amass for the two seasons. A common slope between seasons was also shown for the relationship between SLA and NMass. There was no significant diffeence in slope elevation between summer and winter for the SLA v. Nmass relationship. Trends within relationships among leaf attributes were the same as those found for a wide range of plant species worldwide, but the absolute values were loer than those foudn elsewhere. Therefore the global relationships in terms of trends (positive or negative) that have been determined overseas apply in Australia but the elevation of th sloep and the magnitidue of the slope are reduced (Amass v. Nmass) or increased (Amass v. SLA and Nmass v. SLA) compared with global trends.
Cardoso-Vilhena, J., Balaguer, L., Eamus, D., Ollerenshaw, J. & Barnes, J. 2004, 'Mechanisms underlying the amelioration of O-3-induced damage by elevated atmospheric concentrations of CO2', Journal Of Experimental Botany, vol. 55, pp. 771-781.
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Prior, L.D., Bowman, D. & Eamus, D. 2004, 'Seasonal differences in leaf attributes in Australian tropical tree species: family and habitat comparisons', Functional Ecology, vol. 18, pp. 707-718.
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Hose, G.C., Murray, B. & Eamus, D. 2004, 'Water quality guidelines to protect groundwater-dependent ecosystems', Ecological Management & Restoration, vol. 5, pp. 78-80.
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Zeppel, M.J., Murray, B., Barton, C. & Eamus, D. 2004, 'Seasonal responses of xylem sap velocity to VPD and solar radiation during drought in a stand of native trees in temperate Australia', Functional Plant Biology, vol. 31, pp. 461-470.
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Xylem sap velocity of two dominant tree species, Eucalyptus crebra F. Muell and Callitris glaucophylla J. Thopson & LAS Johnson, in a native remnant forest of eastern Australia was measured in winter and summer during a rpolonged (> 12 months) and extensive drought. The influence of vapour pressure deficit (VPD) and solar radiation levels onthe velocity of sap was determined. Pronounced hysteresis in sap velocity was observed in both species as a function of VPD and solar radiation. However the rotation of the hysteresis curve was clockwise for the response of sap velocity to VPD but anti-clockwise in the response of sap bvelocity to radiation levels. A possible reason for this difference is discussed. The degree of hysteresis (area bounded by the curve) was larger for the VPD response than the response to solar radiation and also varied with season. A simple linear model was able to predict sap velocity from knowledge of VPD and solar radiation in winter and summer. The consistent presence of hysteresis in the response to sap velocity to VPD and solar radiation suggests that large temporal and spatial models of vegetation water use may require soem provision for the different responses of sap velocity, and hence water use, to VPD and solar radiation, between morninga nd afternoon and between seasons.
Chen, X., Eamus, D. & Hutley, L.B. 2004, 'Seasonal patterns of fine-root productivity and turnover in a tropical savanna of northern Australia', Journal of Tropical Ecology, vol. 20, pp. 221-224.
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Macinnis-Ng, C.M., McClenahan, K. & Eamus, D. 2004, 'Convergence in hydraulic architecture, water relations and primary productivity amongst habitats and across seasons in Sydney', Functional Plant Biology, vol. 31, no. 5, pp. 429-439.
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Convergence in leaf traits across biomes demonstrates generality in plant functioning. Relationships between hydraulic architecture and photosynthesis are less well studied. We investigated convergence in minimum leaf water potential (?min), conductivity per sapwood area (ks), Huber value (Hv) and xylem embolism and photosynthesis of several plant species in four habitats (heathland, woodland (ridge-top), woodland (below ridge) and mangrove) across two seasons (summer and winter) in the Sydney region, New South Wales, Australia. The studied species were: Banksia oblongifolia, Angophora hispida and Persoonia lanceolata (heathland); Eucalyptus haemastoma, Angophora hispida and B. oblongifolia (woodland, ridge-top); B. integrifolia, Cissus hypoglauca and Glochidion ferdinandi (woodland, below ridge); and Avicennia marina and Aegiceras corniculatum (mangrove). Seasonality strongly influenced all parameters in all habitats. Winter ?min values were lower than those for summer in the heathland and both woodland habitats, but summer ?min values were lower than those for winter in the mangrove. Summer ks values were higher than winter values in all habitats, while Hv was higher in winter than summer for all habitats.
McClenahan, K., Macinnis-Ng, C.M. & Eamus, D. 2004, 'Hydraulic architecture and water relations of several species at diverse sites around Sydney', Australian Journal of Botany, vol. 52, pp. 509-518.
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Seasonal comparisons of leaf eater potential, root biomass, hydraulic architecture, xylem embolism and xylem dimensions were made for eight woody species in four diverse habitats (mangroves, coastal heathland, ridge-top woodland and river-flat woodland). In most comparisons, pre-dawn and minimum leaf water potentials were lower in winter than in summer, a result attributed tolower raifall and a smaller root biomass in winter tha in summer. Branch hydraulic conductivities (per unit transverse area, sapwood area or leaf area) were generally larger in summer than in winter across all species in all habutats. An invese relationship between Huber value and conductivity was observed across all four habitats. Increased solar radiation and evaportative deman in the summer was associated with an increased percentage loss of xylem conductance arising from embolism, compared with winter. These results are discussed in the context of patterns and relationships among water relations, microcliate and hydraulic architecture.
Prior, L.D., Eamus, D. & Bowman, D. 2004, 'Tree growth rates in north Australian savanna habitats: seasonal patterns and correlations with leaf attributes', Australian Journal Of Botany, vol. 52, pp. 303-314.
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We demonstate a significant relationship between leaf attributes and growth rates of mature trees under natural conditions in northern Australia, a pattern that has not been widely reported before in the literature. Increase in diameter at breast height (DBH) was measured every 3 months for 2 years for 21 tree species from four habitats near Darwin: Eucalyotus open forest, mixed woodland, Melaleuca swamp and dry monsoon rainforest. Assimilation rates and foliar chlorophyll, nitrogen and phosphorus concentrations were positively correlated with growth rate and negatively correlated with leaf mass per area. For most species, increases inDBH were confined to the wet-season (summer) period between November and May. Average annual increases in DBH were larger in the dry monsoon rainforest (0.87 cm) and the Melaleuca swamp (0.65 cm) than in Myrtaceous species (0.25 cm). These results are discussed in relation to the frequent fire regime prevailing over much of northern Australia which causes the marked contrast between the small pockets of fire-tender closed monsoon rainforest and the surrounding large expanses of fr=ire-tolerant savanna.
Eamus, D. 2003, 'How does ecosystem water balance affect net primary productivity of woody ecosystems?', Functional Plant Biology, vol. 30, no. 2, pp. 187-205.
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Murray, B., Zeppel, M.J., Hose, G.C. & Eamus, D. 2003, 'Groundwater-dependent ecosystems in Australia: it's more than just water for rivers', Ecological Management & Restoration, vol. 4, no. 2, pp. 110-113.
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Chen, X., Hutley, L.B. & Eamus, D. 2003, 'Carbon balance of tropical savanna of northern Australia', Oecologia, vol. 137, pp. 405-416.
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Zeppel, M.J., Murray, B. & Eamus, D. 2003, 'The potential impact of dryland salinity on the threatened flora and fauna of New South Wales', Ecological Management & Restoration, vol. 4 (Sup.), pp. 53-59.
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Choinski, J.S., Ralph, P.J. & Eamus, D. 2003, 'Changes in photosynthesis during leaf expansion in Corymbia gummifera', Australian Journal Of Botany, vol. 51, no. 1, pp. 111-118.
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Prior, L.D., Eamus, D. & Bowman, D. 2003, 'Leaf attributes in the seasonally dry tropics: a comparison of four habitats in northern Australia', Functional Ecology, vol. 17, no. 4, pp. 504-515.
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Chen, X., Eamus, D. & Hutley, L.B. 2002, 'Seasonal pattens of soil carbon dioxide efflux from a wet-dry tropical savanna of northern Australia', Australian Journal of Botany, vol. 50, no. N/A, pp. 43-51.
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Eamus, D., Chen, X., Hutley, L.B. & Kelly, G. 2002, 'Root biomass and root fractal analyses of an open Eucalyptus forest in a savanna of north Australia', Australian Journal of Botany, vol. 50, no. N/A, pp. 31-41.
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Thomas, D.D. & Eamus, D. 2002, 'Seasonal patterns of xylem sap pH, cylem abscisic acid concentration, leaf water potential and stomatal conductance of six evergreen and deciduous Australian savanna tree species', Australian Journal of Botany, vol. 50, no. N/A, pp. 229-236.
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Chen, X.Y., Eamus, D. & Hutley, L.B. 2002, 'Seasonal patterns of soil carbon dioxide efflux from a wet-dry tropical savanna of northern Australia (vol 50, pg 43, 2002)', AUSTRALIAN JOURNAL OF BOTANY, vol. 50, no. 3, pp. 373-U20.
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Eamus, D. & Shanahan, S.T. 2002, 'A rate equation model of stomatal responses to vapour pressure deficit and drought.', BMC ecology, vol. 2, p. 8.
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BACKGROUND: Stomata respond to vapour pressure deficit (D) - when D increases, stomata begin to close. Closure is the result of a decline in guard cell turgor, but the link between D and turgor is poorly understood. We describe a model for stomatal responses to increasing D based upon cellular water relations. The model also incorporates impacts of increasing levels of water stress upon stomatal responses to increasing D. RESULTS: The model successfully mimics the three phases of stomatal responses to D and also reproduces the impact of increasing plant water deficit upon stomatal responses to increasing D. As water stress developed, stomata regulated transpiration at ever decreasing values of D. Thus, stomatal sensitivity to D increased with increasing water stress. Predictions from the model concerning the impact of changes in cuticular transpiration upon stomatal responses to increasing D are shown to conform to experimental data. Sensitivity analyses of stomatal responses to various parameters of the model show that leaf thickness, the fraction of leaf volume that is air-space, and the fraction of mesophyll cell wall in contact with air have little impact upon behaviour of the model. In contrast, changes in cuticular conductance and membrane hydraulic conductivity have significant impacts upon model behaviour. CONCLUSION: Cuticular transpiration is an important feature of stomatal responses to D and is the cause of the 3 phase response to D. Feed-forward behaviour of stomata does not explain stomatal responses to D as feedback, involving water loss from guard cells, can explain these responses.
Eamus, D., Chen, X., Kelley, G. & Hutley, L.B. 2002, 'Root biomass and root fractal analyses of an open Eucalyptus forest in a savanna of north Australia', AUSTRALIAN JOURNAL OF BOTANY, vol. 50, no. 1, pp. 31-41.
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Chen, X., Eamus, D. & Hutley, L.B. 2002, 'Erratum: Seasonal patterns of soil carbon dioxide efflux from a wet-dry tropical savanna of northern Australia (Australian Journal of Botany)', Australian Journal of Botany, vol. 50, no. 3, p. 373.
Chen, X.Y., Eamus, D. & Hutley, L.B. 2002, 'Seasonal patterns of soil carbon dioxide efflux from a wet-dry tropical savanna of northern Australia', AUSTRALIAN JOURNAL OF BOTANY, vol. 50, no. 1, pp. 43-51.
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Thomas, D.S. & Eamus, D. 2002, 'Seasonal patterns of xylem sap pH, xylem abscisic acid concentration, leaf water potential and stomatal conductance of six evergreen and deciduous Australian savanna tree species', AUSTRALIAN JOURNAL OF BOTANY, vol. 50, no. 2, pp. 229-236.
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Eamus, D., Hutley, L.B. & O'Grady, A.P. 2001, 'Daily and Seasonal Patterns of Carbon and Water Fluxes Above a North Australian Savanna', Tree Physiology, vol. 21, pp. 977-988.
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Daily and seasonal fluxes of carbon dioxide and water vapor above a north Australian savanna were recorded over a complete dry seasonwet season annual cycle using the eddy covariance technique. Wet season rates of photosynthesis and transpiration were larger than those measured in the dry season and were dominated by the presence of the grassy understory. As the dry season progressed and the grass understory died, ecosystem rates of assimilation and water vapor flux declined substantially. By the end of the dry season, canopy assimilation and evapotranspiration rates were 2025% of wet season values. Assimilation was light saturated in the dry season but not in the wet season. Stomatal control of transpiration increased between the wet and dry season. This was revealed by the decline in the slope of E with increasing leaf-to-air vapor pressure difference (D) between wet and dry seasons, and also by the significant decrease in the ratio of boundary to canopy conductance observed between the wet and dry seasons. A simple pan-tropical modeling of leaf area index or wet season canopy CO2 flux was undertaken. It was shown that with readily available data for foliar N content and the ratio of rainfall to potential evaporation, leaf index and wet season canopy CO2 flux can be successfully estimated for a number of tropical ecosystems, including north Australian savannas.
Eamus, D. & Prior, L.D. 2001, 'Ecophysiology of Trees of Seasonally Dry Tropics: Comparisons Among Phenologies', Advances in Ecological Research, vol. 32, pp. 113-197.
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Hutley, L.B., O'Grady, A.P. & Eamus, D. 2001, 'Monsoonal Influences on Evapotranspiration of Savanna Vegetation of Northern Australia', Oecologia, vol. 126, pp. 434-443.
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Prior, L.D. & Eamus, D. 2000, 'Seasonal Changes In Hydraulic Conductance, Xylem Embolism And Leaf Area In Eucalyptus Tetrodonta And Eucalyptus Miniata Saplings In A North Australian Savanna', Plant Cell And Environment, vol. 23, no. 9, pp. 955-965.
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Eucalypt saplings in north Australian savannas commonly die back, sometimes to ground level, during the 5 months of the long dry season, Wafer potentials are lower in saplings than large trees during the dry season, and we hypothesized that low water pot
Fordyce, I., Eamus, D. & Duff, G. 2000, 'Episodic Seedling Growth In Allosyncarpia Ternata, A Lignotuberous, Monsoon Rainforest Tree In Northern Australia', Austral Ecology, vol. 25, no. 1, pp. 25-35.
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On the western Arnhem Land Plateau, Northern Territory, Australia, seedlings of the canopy tree Allosyncarpia ternata S.T. Blake typically spend many years (perhaps decades) as small (< 1 m), multistemmed plants on the forest floor. In this establishment
Thomas, D.W., Eamus, D. & Shanahan, S. 2000, 'Influence Of Season, Drought And Xylem Aba On Stomatal Responses To Leaf-To-Air Vapour Pressure Difference Of Trees Of The Australian Wet-Dry Tropics', Australian Journal Of Botany, vol. 48, no. 2, pp. 143-151.
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This paper reports the results of two experiments undertaken to investigate the influence of season and soil drying on stomatal responses to leaf-to-air vapour pressure differences. We examined the response of stomatal conductance to increasing leaf-to-a
O'Grady, A.P., Chen, X., Eamus, D. & Hutley, L.B. 2000, 'Composition, Leaf Area Index And Standing Biomass Of Eucalypt Open Forests Near Darwin In The Northern Territory, Australia', Australian Journal Of Botany, vol. 48, no. 5, pp. 629-638.
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Savanna communities dominate the wet dry tropical regions of the world and are an important community type in monsoonal northern Australia. As such they have a significant impact on the water and carbon balance of this region. Above the 1200-mm isohyet,
Eamus, D., O'Grady, A.P. & Hutley, L.B. 2000, 'Dry Season Conditions Determine Wet Season Water Use In The Wet-Dry Tropical Savannas Of Northern Australia', Tree Physiology, vol. 20, no. 18, pp. 1219-1226.
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Daily and seasonal patterns of transpiration were measured in evergreen eucalypt trees growing at a wet (Darwin), intermediate (Katherine) and dry site (Newcastle Waters) along a steep rainfall gradient in a north Australian savanna. Relationships betwee
Hutley, L.B., O'Grady, A.P. & Eamus, D. 2000, 'Evapotranspiration From Eucalypt Open-Forest Savanna Of Northern Australia', Functional Ecology, vol. 14, no. 2, pp. 183-194.
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1. Using three independent methods (eddy covariance, heat pulse and open-top chambers), diurnal and seasonal measurements of evapotranspiration were made in a wet-dry Eucalypt savanna of the Northern Territory, Australia. 2. Total annual dry-canopy water
Fordyce, I.R., Eamus, D. & Duff, G.A. 2000, 'Episodic seedling growth in Allosyncarpia ternata, a lignotuberous, monsoon rainforest tree in northern Australia', Austral Ecology, vol. 25, no. 1, pp. 25-35.
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On the western Arnhem Land Plateau, Northern Territory, Australia, seedlings of the canopy tree Allosyncarpia ternata S.T. Blake typically spend many years (perhaps decades) as small (< 1 m), multistemmed plants on the forest floor. In this establishment phase, long periods of apparent inactivity are interrupted by episodes of rapid growth. This paper describes a 5-year field-monitoring program to examine the pattern of seedling growth and survival in allosyncarpia forest, and field and shadehouse measurements of lignotuber size. Individual seedlings may produce, each wet season, a number of fast-growing stems, which then die back in the following dry season. As a result, mean annual above-ground growth during this life stage is negligible. With each wet season, however, the seedling extends its below ground parts - a large lignotuber and a deep root system. After a number of years, when the lignotuber has grown large enough to sustain massive shoot growth, when a suitable light gap becomes available, and presumably when roots reach reliable dry-season water supplies, the seedling grows rapidly. Thus, the shortage of saplings in allosyncarpia forest is due to the short time that individual plants spend at that particular growth-stage, rather than to any dysfunction in recruitment.
Williams, R.P., Myers, B., Eamus, D. & Duff, G. 1999, 'Reproductive Phenology Of Woody Species In A North Australian Tropical Savanna', Biotropica, vol. 31, no. 4, pp. 626-636.
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Interspecific and interannual variation in reproductive phenology was quantified for 50 common species of trees and shrubs from a mesic savanna near Darwin, northern Australia. The presence of buds, Bowers, and fruit was noted over a 30-month period, fro
Eamus, D., Myers, B., Duff, G. & Williams, D.J. 1999, 'Seasonal Changes In Photosynthesis Of Eight Savanna Tree Species', Tree Physiology, vol. 19, no. 10, pp. 665-671.
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Seasonal variations in carbon assimilation of eight tree species of a north Australian tropical savanna were examined over two wet seasons and one dry season (18 months). Assimilation rates (A) in the two evergreen species, Eucalyptus tetrodonta F Muell.
O'Grady, A.P., Eamus, D. & Hutley, L.B. 1999, 'Transpiration Increases During The Dry Season: Patterns Of Tree Water Use In Eucalypt Open-Forests Of Northern Australia', Tree Physiology, vol. 19, no. 9, pp. 591-597.
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Australian savannas exhibit marked seasonality in precipitation, with more than 90% of the annual total falling between October and May. The dry season is characterized by declining soil water availability and high vapor pressure deficits (up to 2.5 kPa)
Thomas, D.W., Eamus, D. & Bell, D.R. 1999, 'Optimization Theory Of Stomatal Behaviour - Ii. Stomatal Responses Of Several Tree Species Of North Australia To Changes In Light, Soil And Atmospheric Water Content And Temperature', Journal Of Experimental Botany, vol. 50, no. 3, pp. 393-400.
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In a companion paper several methods of calculating the marginal unit water cost of plant carbon gain (partial derivative E/partial derivative A) were tested to determine whether stomata were behaving optimally in relation to regulating leaf gas exchange
Eamus, D., Myers, B., Duff, G. & Williams, R.P. 1999, 'A Cost-Benefit Analysis Of Leaves Of Eight Australian Savanna Tree Species Of Differing Leaf Life-Span', Photosynthetica, vol. 36, no. 4, pp. 575-586.
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Cost-benefit analyses of foliar construction and maintenance costs and of carbon assimilation of leaves of differing life-span were conducted using two evergreen, three semi-deciduous, and three deciduous tree species of savannas of north Australia. Rate
Eamus, D. 1999, 'Ecophysiological Traits Of Deciduous And Evergreen Woody Species In The Seasonally Dry Tropics', Trends In Ecology & Evolution, vol. 14, no. 1, pp. 11-16.
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Seasonally dry tropical ecosystems occur in the Americas, Africa, India and Australia. They sustain large human populations, determine regional climate, are sites of biological and cultural conservation, and have significant economic value. Evergreen, de
Thomas, D.W. & Eamus, D. 1999, 'The Influence Of Predawn Leaf Water Potential On Stomatal Responses To Atmospheric Water Content At Constant C-I And On Stem Hydraulic Conductance And Foliar Aba Concentrations', Journal Of Experimental Botany, vol. 50, no. 2, pp. 243-251.
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Stomatal and photosynthetic responses to increasing leaf-to-air vapour pressure difference (V) were investigated in watered and droughted Eucalyptus tetrodonta when either ambient CO2 (C-a) or internal CO2 concentration (C-i) were constant, Stem hydrauli
Prior, L.D. & Eamus, D. 1999, 'Seasonal Changes In Leaf Water Characteristics Of Eucalyptus Tetrodonta And Terminalia Ferdinandiana Saplings In A Northern Australian Savanna', Australian Journal Of Botany, vol. 47, no. 4, pp. 587-599.
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The monsoonal areas of northern Australia experience extreme seasonal variations in rainfall, with an annual dry season of 7 months or more. Seasonal changes in leaf water relations were investigated for saplings of two tree species common in northern Au
Thomas, D.W., Eamus, D. & Bell, D.R. 1999, 'Optimization Theory Of Stomatal Behaviour - I. A Critical Evaluation Of Five Methods Of Calculation', Journal Of Experimental Botany, vol. 50, no. 3, pp. 385-392.
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There are two principal aims in this first manuscript, first, to compare five methods for calculating the marginal unit water cost of plant carbon gain (partial derivative E/partial derivative A) of leaves of two Australian tropical tree species, and sec
Thomas, D.S., Eamus, D. & Bell, D. 1999, 'Optimization theory of stomatal behaviour - I. A critical evaluation of five methods of calculation', JOURNAL OF EXPERIMENTAL BOTANY, vol. 50, no. 332, pp. 385-392.
Thomas, D.S., Eamus, D. & Bell, D. 1999, 'Optimization theory of stomatal behaviour - II. Stomatal responses of several tree species of north Australia to changes in light, soil and atmospheric water content and temperature', JOURNAL OF EXPERIMENTAL BOTANY, vol. 50, no. 332, pp. 393-400.
Thomas, D.S. & Eamus, D. 1999, 'The influence of predawn leaf water potential on stomatal responses to atmospheric water content at constant C-i and on stem hydraulic conductance and foliar ABA concentrations', JOURNAL OF EXPERIMENTAL BOTANY, vol. 50, no. 331, pp. 243-251.
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Eamus, D. & Prichard, H. 1998, 'A Cost-Benefit Analysis Of Leaves Of Four Australian Savanna Species', Tree Physiology, vol. 18, no. 8-Sep, pp. 537-545.
We conducted a cost-benefit analysis of the contrasting phenologies of two evergreen and two deciduous species of the savannas of north Australia. Stomatal conductance, rates of light-saturated assimilation (A(max)) and dark respiration were measured for
Myers, B., Williams, R.P., Fordyce, I., Duff, G. & Eamus, D. 1998, 'Does Irrigation Affect Leaf Phenology In Deciduous And Evergreen Trees Of The Savannas Of Northern Australia?', Australian Journal Of Ecology, vol. 23, no. 4, pp. 329-339.
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Soil moisture was augmented experimentally during two successive dry seasons and the intervening wet season in a humid tropical savanna in Danwin, northern Australia. Leaf phenology was monitored in four common tree species Terminalia ferdinandiana and P
Thomas, D.W., Turner, D.W. & Eamus, D. 1998, 'Independent Effects Of The Environment On The Leaf Gas Exchange Of Three Banana (Musa Sp.) Cultivars Of Different Genomic Constitution', Scientia Horticulturae, vol. 75, no. 1-2, pp. 41-57.
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Circumstantial evidence suggests that the Musa balbisiana (B) genome confers greater drought tolerance to bananas and plantains than the Musa acuminata (A) genome. Hence the genetic makeup of bananas and plantains may affect the response of leaf gas exch
Cook, P., Hatton, T., Pidsley, D., Herczeg, A., Held, A., O'Grady, A.P. & Eamus, D. 1998, 'Water Balance Of A Tropical Woodland Ecosystem, Northern Australia: A Combination Of Micro-Meteorological, Soil Physical And Groundwater Chemical Approaches', Journal Of Hydrology, vol. 210, no. 1-4, pp. 161-177.
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A combination of micro-meteorological, soil physical and groundwater chemical methods enabled the water balance of a tropical eucalypt savanna ecosystem in Northern Australia to be estimated. Heat pulse and eddy correlation were used to determine oversto
Eamus, D. & Prichard, H. 1998, 'A cost-benefit analysis of leaves of four Australian savanna species.', Tree physiology, vol. 18, no. 8_9, pp. 537-545.
We conducted a cost-benefit analysis of the contrasting phenologies of two evergreen and two deciduous species of the savannas of north Australia. Stomatal conductance, rates of light-saturated assimilation (A(max)) and dark respiration were measured for six leaves from each of five or six trees. These leaves were then analyzed for total nitrogen, ether-soluble lipids, ash content, and heat of combustion. Construction and maintenance costs, nitrogen-use efficiencies and instantaneous transpiration efficiencies were then calculated from these data. Evergreen species had significantly lower specific leaf area, leaf nitrogen and leaf ash content than deciduous species. Evergreen species also had significantly higher heat of combustion and lipid content of crude extracts than deciduous species. Light-saturated assimilation rates were higher in evergreen species on a leaf area basis, but were higher in deciduous species on a leaf dry weight basis. In both evergreen and deciduous species, A(max) and total Kjeldahl nitrogen were linearly related. Similarly, nitrogen-use efficiency did not differ among species. Leaf construction costs were significantly higher for evergreen species than for deciduous species, but maintenance costs did not differ among species. Evergreen species had a higher cost:benefit ratio than deciduous species but because of their longer-lived leaves, the payback interval was longer in evergreen species than in deciduous species. These results support the hypotheses that: (1) longer-lived leaves are more expensive to construct than shorter-lived leaves, and (2) there is a higher investment of nitrogen into short-lived leaves to support a higher A(max) over a shorter payback interval. We conclude that deciduous and evergreen species partition resources both temporally and spatially, thereby reducing interspecies competition.
Fordyce, I., Eamus, D., Duff, G. & Williams, R.P. 1997, 'The Role Of Seedling Age And Size In The Recovery Of Allosyncarpia Ternata Following Fire', Australian Journal Of Ecology, vol. 22, no. 3, pp. 262-269.
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This paper examines the effects of seedling size and age on fire tolerance of Allosyncarpia ternata (Myrtaceae), a dominant tree in patches of monsoon rainforest of the wet-dry tropics in the Northern Territory, Australia. We address the following questi
Goodfellow, J., Eamus, D. & Duff, G. 1997, 'The Impact Of Co2 Enrichment On Assimilation, Stomatal Conductance And Growth In A Long-Term Study Of Mangifera Indica In The Wet-Dry Tropics Of Australia.', Plant Physiology, vol. 114, no. 3, pp. 480-480.
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Prior, L.D., Eamus, D. & Duff, G. 1997, 'Seasonal and Diurnal Patterns of Carbon Assimilation, Stomatal Conductance and Leaf Water Potential in Eucalyptus tetrodonta Saplings in a WetDry Savanna in Northern Australia', Australian Journal Of Botany, vol. 45, no. 2, pp. 241-258.
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Seasonal and diurnal trends in carbon assimilation, stomatal conductance and leaf water potential were studied using 1-3 m tall saplings of Eucalyptus tetrodonta (F.Muell.). The study site was in an unburnt savanna near Darwin, where rainfall is strongly
Fordyce, I., Duff, G. & Eamus, D. 1997, 'The Water Relations Of Allosyncarpia Ternata (Myrtaceae) At Contrasting Sites In The Monsoonal Tropics Of Northern Australia', Australian Journal Of Botany, vol. 45, no. 2, pp. 259-274.
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Allosyncarpia ternata S.T.Blake (Myrtaceae) is an evergreen tree, restricted largely to rocky habitats on the Arnhem Land Plateau in the wet-dry tropics of northern Australia. Allosyncarpia ternata grows in a wide range of habitats, including sites near
Eamus, D. & Cole, S. 1997, 'Diurnal And Seasonal Comparisons Of Assimilation, Phyllode Conductance And Water Potential, Of Three Acacia And One Eucalyptus Species In The Wet-Dry Tropics Of Australia', Australian Journal Of Botany, vol. 45, no. 2, pp. 275-290.
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Four species of tropical tree (Acacia auriculiformis Cunn. ex Benth., A. mangium Willd., A. crassicarpa Cunn. ex Benth. and Eucalyptus pellita F.Muell.) were studied at a site on Melville Island, off the north coast of the Northern Territory of Australia
Goodfellow, J., Eamus, D. & Duff, G. 1997, 'Diurnal And Seasonal Changes In The Impact Of CO2 Enrichment On Assimilation, Stomatal Conductance And Growth In A Long-Term Study Of Mangifera Indica In The Wet-Dry Tropics Of Australia', Tree Physiology, vol. 17, no. 5, pp. 291-299.
We studied assimilation, stomatal conductance and growth of Mangifera indica L. saplings during long-term exposure to a CO2-enriched atmosphere in the seasonally wet-dry tropics of northern Australia. Grafted saplings of M. indica were planted in the gro
Williams, R.P., Myers, B., Muller, W.J., Duff, G. & Eamus, D. 1997, 'Leaf Phenology Of Woody Species In A North Australian Tropical Savanna', Ecology, vol. 78, no. 8, pp. 2542-2558.
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Leaf phenology was monitored for 49 woody species (trees and tall shrubs) each month over a 2.5-year period in a humid, wet-dry tropical eucalypt savanna at Solar Village, near Darwin, Australia. In the 10 most common species, which spanned the range of
Myers, B., Duff, G., Eamus, D., Fordyce, I., O'Grady, A.P. & Williams, R.P. 1997, 'Seasonal Variation In Water Relations Of Trees Of Differing Leaf Phenology In A Wet-Dry Tropical Savanna Near Darwin, Northern Australia', Australian Journal Of Botany, vol. 45, no. 2, pp. 225-240.
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The seasonal variation in leaf xylem pressure potential at dawn (psi(dawn)), leaf tissue water characteristics and daily maximum leaf conductance was measured in eight woody species in a wet-dry tropical savanna near Darwin, northern Australia, between O
Prior, L.D., Eamus, D. & Duff, G. 1997, 'Seasonal Trends In Carbon Assimilation, Stomatal Conductance, Pre-Dawn Leaf Water Potential And Growth In Terminalia Ferdinandiana, A Deciduous Tree Of Northern Australian Savannas', Australian Journal Of Botany, vol. 45, no. 1, pp. 53-69.
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Seasonal trends in pre-dawn leaf water potential and morning and afternoon rates of light-saturated assimilation and stomatal conductance were studied in saplings of the deciduous tree Terminalia ferdinandiana Excell. Mean daily maximum assimilation rate
Duff, G., Myers, B., Williams, R.P., Eamus, D., O'Grady, A.P. & Fordyce, I. 1997, 'Seasonal Patterns In Soil Moisture, Vapour Pressure Deficit, Tree Canopy Cover And Pre-Dawn Water Potential In A Northern Australian Savanna', Australian Journal Of Botany, vol. 45, no. 2, pp. 211-224.
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The wet-dry tropics of northern Australia are characterised by extreme seasonal variation in rainfall and atmospheric vapour:pressure deficit, although temperatures are relatively constant throughout the year. This seasonal variation is associated with m
Williams, J.S. & Eamus, D. 1997, 'Plant Ecophysiology: Linking Pattern And Process - A Review', Australian Journal Of Botany, vol. 45, no. 2, pp. 351-357.
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The Symposium `Plant Ecophysiology: Linking Pattern and Process was held as part of the 1995 meeting of the Ecological Society of Australia (ESA). The aim of the Symposium was to highlight work that examined mechanisms underlying ecological patterns and linked them to ecological and/or evolutionary processes. Another aim was to expose ecologists to the methods available to examine the mechanistic and functional basis of the organisms and systems under study. Much early ecological research has been concerned with the description and classification of vegetation types, with relatively little effort devoted to understanding the underlying processes that determined distribution. A more quantitative approach based on knowledge of the underlying mechanisms can further improve understanding of systems. This was amply demonstrated in a Symposium on the effects of elevated atmospheric CO2 on vegetation dynamics, also held in conjunction with an ESA meeting (see papers in Australian Journal of Botany, Volume 40(2)). Recent technological advances have stimulated rapid progress in the field of ecophysiology and hence an increasing process-based understanding is developing.
Landrigan, M., Morris, S.C., Eamus, D. & McGlasson, B. 1996, 'Postharvest Water Relationships And Tissue Browning Of Rambutan Fruit', Scientia Horticulturae, vol. 66, no. 3-Apr, pp. 201-208.
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The water status of excised spinterns or spintern plus pericarp and attached endocarp of rambutan fruits was measured three times during storage at 20 degrees C, Changes in fruit colour were also recorded. The development of browning was preceded by wate
Eamus, D. 1996, 'Tree Responses To Co2 Enrichment: Co2 And Temperature Interactions, Biomass Allocation And Stand-Scale Modeling', Tree Physiology, vol. 16, no. 1-2, pp. 43-47.
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In this review, I focus on modeling studies of tree responses to CO2 enrichment. First, I examine leaf-scale models of assimilation with respect to the interaction between low temperature and CO2 enrichment. Second, because changes in allocation within a
O'Grady, A.P., Mcguinness, K. & Eamus, D. 1996, 'The Abundance And Growth Of Avicennia Marina And Rhizophora Stylosa In The Low Shore Zone Of Darwin Harbour, Northern Territory', Australian Journal Of Ecology, vol. 21, no. 3, pp. 272-279.
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The growth and distribution of the two mangrove seedling species, Avicennia marina (Forsk.) Vierh, and Rhizophora stylosa Griff., were studied in the low-shore zone at three locations along two estuaries of Darwin Harbour to determine how growth varied a
O'Grady, A.P., Mcguinness, K.A. & Eamus, D. 1996, 'The abundance and growth of Avicennia marina and Rhizophora stylosa in the low shore zone of Darwin Harbour, Northern Territory', Austral Ecology, vol. 21, no. 2, pp. 272-279.
The growth and distribution of the two mangrove seedling species, Avicennia marina (Forsk.) Vierh. and Rhizophora stylosa Griff., were studied in the low-shore zone at three locations along two estuaries of Darwin Harbour to determine how growth varied along the estuary and within the habitats of the low shore zone. The low shore environment was heterogenous for factors such as salinity and light, with substantial variation within and between locations. Seedlings of Avicennia were in higher densities in light gaps than in the adjacent forest, and density in both habitats decreased towards the mouth of the estuary. Growth of Avicennia seedlings, as measured through in situ growth trials and plant harvests, increased towards the mouth of the estuary. Results for Rhizophora seedlings were more complex although some similar trends were evident. This may have been due to the greater early survival of Rhizophora seedlings compared to Avicennia seedlings. The importance of propagule origin was investigated, for Rhizophora, by transplanting propagules between locations along one estuary. Increased seedling survival was observed at the propagule source site; however, this effect was subtle and probably not the most important factor affecting seedling survival at a site.
Eamus, D. 1996, 'Responses of field grown trees to CO2 enrichment', Commonwealth Forestry Review, no. 240, pp. 39-47.
The concentration of atmospheric CO2 has increased substantially since the start of the Industrial Revolution. CO2 is central to the growth and physiology of plants and thus changes in its concentration influence plants directly and indirectly. Trees, because of their longevity, economic importance and role in the global carbon cycle, have been extensively studied in relation to vegetation responses to climate change. To date, the majority of investigations have relied upon juvenile material because of the physical problems of working with large mature trees. However recent developments in techniques, including open-top-chambers, branch bags and free-air-carbon-enrichment studies have allowed more mature tissue to be studied than previously. This review briefly describes these techniques and discusses some recent results. Recent developments in the understanding of potential mechanisms underlying tree responses to CO2 enrichment are reported.
Eamus, D. 1996, 'Responses of field grown trees to CO2 enrichment', Commonwealth Forestry Review, vol. 75, no. 1, pp. X3-X4.
The concentration of atmospheric CO2 has increased substantially since the start of the Industrial Revolution. CO2 is central to the growth and physiology of plants and thus changes in its concentration influence plants directly and indirectly. Trees, because of their longevity, economic importance and role in the global carbon cycle, have been extensively studied in relation to vegetation responses to climate change. To date, the majority of investigations have relied upon juvenile material because of the physical problems of working with large mature trees. However recent developments in techniques, including open-top-chambers, branch bags and free-air-carbon-enrichment studies have allowed more mature tissue to be studied than previously. This review briefly describes these techniques and discusses some recent results. Recent developments in the understanding of potential mechanisms underlying tree responses to CO2 enrichment arc reported.
Eamus, D. 1996, 'Tree responses to CO(2) enrichment: CO(2) and temperature interactions, biomass allocation and stand-scale modeling.', Tree physiology, vol. 16, no. 1_2, pp. 43-47.
In this review, I focus on modeling studies of tree responses to CO(2) enrichment. First, I examine leaf-scale models of assimilation with respect to the interaction between low temperature and CO(2) enrichment. Second, because changes in allocation within a tree may be significant in determining the growth response of trees to CO(2) enrichment and low temperatures, I review models of the control of allocation in plants. Finally, models of stand-scale processes are discussed with respect to their ability to make reliable estimates of likely vegetation responses to predicted climate change. I conclude that our ability to make reliable predictions is hindered by our lack of understanding of several processes, namely: the interaction between increased atmospheric CO(2) concentration and low temperatures; the control of allocation in plants; and the modeling of stand-scale processes.
Fordyce, I., Duff, G. & Eamus, D. 1995, 'The Ecophysiology Of Allosyncarpia-Ternata (Myrtaceae) In Northern Australia - Tree Physiognomy, Leaf Characteristics And Assimilation At Contrasting Sites', Australian Journal Of Botany, vol. 43, no. 4, pp. 367-377.
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Allosyncarpia ternata S.T.Blake, a large, evergreen tree endemic to the northern part of the Northern Territory, Australia, dominates the canopy in a wide variety of habitats, including monsoon rainforest on ravine floors, open forest and woodland on cli
Eamus, D., Berryman, C. & Duff, G. 1995, 'The Impact Of Co2 Enrichment On Water Relations In Maranthes-Corymbosa And Eucalyptus-Tetrodonta', Australian Journal Of Botany, vol. 43, no. 3, pp. 273-282.
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Seeds of Maranthes corymbosa Blume and Eucalyptus tetrodonta F.Muell were sown under ambient or CO2 enriched conditions (two replicate tents per treatment) in tropical Australia and allowed to grow, rooted in the ground, for 20 months. For both species,
Eamus, D., Duff, G. & Berryman, C. 1995, 'Photosynthetic Responses To Temperature, Light Flux-Density, Co2 Concentration And Vapor-Pressure Deficit In Eucalyptus Tetrodonta Crown Under Co2 Enrichment', Environmental Pollution, vol. 90, no. 1, pp. 41-49.
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Seeds of Eucalyptus tetrodonta were sown under ambient or CO2 enriched (700 mu l litre(-1)) conditions in tropical Australia. Four sets of measurements were made, the first two after 12 months, on trees growing either in pots or planted in the ground. Th
Cole, S., Woo, K., Eamus, D., Harwood, C. & Haines, M. 1994, 'Field-Measurements Of Net Photosynthesis And Related Parameters In 4 Provenances Of Acacia-Auriculiformis', Australian Journal Of Botany, vol. 42, no. 4, pp. 457-470.
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Tree diameter at breast height (DBH), tree height, maximum light saturated assimilation (A(max)), phyllode conductance (g(s)), and phyllode water potential (psi(W)) were determined in trees of Acacia auriculiformis A. Cunn. ex Benth., 3-4 years old. Tree
Duff, G., Berryman, C. & Eamus, D. 1994, 'Growth, Biomass Allocation And Foliar Nutrient Contents Of 2 Eucalyptus Species Of The Wet Dry Tropics Of Australia Grown Under Co2 Enrichment', Functional Ecology, vol. 8, no. 4, pp. 502-508.
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1. Seeds of Eucalyptus tetrodonta and E. miniata were sown in duplicated air-conditioned tents which were ventilated with either ambient or CO2-enriched (700 mumol mol-1) air. Growth, foliar nutrient content, soluble protein and biomass allocation were i
Berryman, C., Eamus, D. & Duff, G. 1994, 'Stomatal Responses To A Range Of Variables In 2 Tropical Tree Species Grown With Co2, Enrichment', Journal Of Experimental Botany, vol. 45, no. 5, pp. 539-546.
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Seedlings of Maranthes corymbosa (Blume) and Eucalyptus tetrodonta (F. Muell) were grown with or without CO2 enrichment (700 mu mol CO2 mol(-1)). The response of stomatal conductance (g(s)) to leaf drying, exogenous abscisic acid and calcium ions was inv
Berryman, C.A., Eamus, D. & Duff, G.A. 1994, 'Stomatal responses to a range of variables in two tropical tree species grown with CO2 enrichment', Journal of Experimental Botany, vol. 45, no. 5, pp. 539-546.
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Seedlings of Maranthes corymbosa (Blume) and Eucalyptus tetrodonta (F. Muell) were grown with or without CO2 enrichment (700mol CO2 mol-1 The response of stomatal conductance (g2) to leaf drying, exogenous absclslc acid and calcium ions was investigated in M. corymbosa. Reciprocal transfer experiments were also conducted whereby plants were grown in one treatment and then transferred to the other before g, was measured.Stomatal conductance in M. corymbosa was more sensitive (a greater percentage decline in g2 per unit percentage decline in leaf fresh weight) to leaf water status under conditions of CO2 enrichment compared to ambient conditions. However, the rate of reduction of g2 in response to exogenous abscisic acid was not influenced by CO2 treatment. In contrast, the rate of reduction of g2, in response to exogenous CaCl2 was decreased under conditions of CO2 enrichment.Reciprocal transfer experiments showed that expo sure to CO2 enrichment results in a short-term, reversible decline in g2, as a result of decreased stomatal aperture and a long-term, irreversible decline in g2 as a result of a decreased stomatal density.Seedlings of E. tetrodonta were used to investigate the response of g2 to light flux density, leaf-to-air vapour pressure difference (LAVPD), leaf internal CO2 concentration (C1 and temperature. Reciprocal transfer experiments were also conducted. CO2 enrichment did not influence the pattern or sensitivity of response of g to LAVPD and C in E. tetrodonta. In contrast, the slope of the response of g2, to temperature decreased for trees grown under elevated [CO2]a conditions and the equilibrium g2 attained at saturating light was also decreased for plants grown under elevated [CO2a. conditions. &copy; 1994 Oxford University Press.
Eamus, D., Berryman, C. & Duff, G. 1993, 'Assimilation, Stomatal Conductance, Specific Leaf-Area And Chlorophyll Responses To Elevated Co2 Of Maranthes Corymbosa, A Tropical Monsoon Rain-Forest Species', Australian Journal Of Plant Physiology, vol. 20, no. 6, pp. 741-755.
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Seeds of Maranthes corymbosa Blume, a monsoon rain forest species of northern Australia, were sown under ambient or elevated CO2 concentrations in tropical Australia. Seedlings were grown under conditions of photon flux density, temperature and atmospher
Wiebel, J., Eamus, D., Chacko, E.K., Downton, W. & Ludders, P. 1993, 'Gas-Exchange Characteristics Of Mangosteen (Garcinia-Mangostana L) Leaves', Tree Physiology, vol. 13, no. 1, pp. 55-69.
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Gas exchange responses of mangosteen (Garcinia mangostana L.) leaves to photosynthetic photon flux density (PPFD), internal CO2 concentration (C(i)), leaf-air vapor pressure deficit (VPD), leaf temperature (T(l)) and time of day were investigated in plan
Berryman, C., Eamus, D. & Duff, G. 1993, 'The Influence Of CO2 Enrichment On Growth, Nutrient Content And Biomass Allocation Of Maranthes-Corymbosa', Australian Journal Of Botany, vol. 41, no. 2, pp. 195-209.
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Seedlings of Maranthes corymbosa Blume, an evergreen tree of tropical Australia and Indonesia were grown for 32 weeks under conditions of ambient and elevated (700 mumol CO2 mol-1) CO2 in tropical northern Australia. Seedlings were exposed to ambient tem
Eamus, D. 1993, 'Assimilation And Stomatal Conductance Responses Of Red Spruce To Midwinter Frosts And The Constituent Ions Of Acid Mist', Tree Physiology, vol. 13, no. 2, pp. 145-155.
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Red spruce (Picea rubens Sarg.) seedlings growing outside in open-top chambers were sprayed twice weekly with artificial mists at either pH 2.5 or 5.6, for five months during the 1988 growing season. The mists contained one of the following: (water, pH 5
Eamus, D. & Murray, M. 1993, 'The Impact Of Constituent Ions Of Acid Mist On Assimilation And Stomatal Conductance Of Norway Spruce Prior And Post Midwinter Freezing', Environmental Pollution, vol. 79, no. 2, pp. 135-142.
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Norway spruce seedlings were sprayed twice weekly with one of a range of artificial mists at either pH 2.5, 3.0 or 5.6, for three months. The mists consisted of either (NH4)2SO4 (pH 5-6), NH4NO3 (pH 5-6), water (pH 5-6), HNO3 (Ph 2.5), HSO4 (pH 2-5 or pH
Eamus, D. 1991, 'The Interaction Of Rising CO2 And Temperatures With Water-Use Efficiency', Plant Cell And Environment, vol. 14, no. 8, pp. 843-852.
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Recent data concerning the impact of elevated atmospheric CO2 upon water use efficiency (WUE) and the related measure, instantaneous transpiration efficiency (ITE), are reviewed. It is concluded from both short and long-term studies that, at the scale of
Berryman, C., Eamus, D. & Farrar, J. 1991, 'Water Relations Of Leaves Of Barley Infected With Brown Rust', Physiological And Molecular Plant Pathology, vol. 38, no. 6, pp. 393-405.
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The water balance of brown rust (Puccinia hordei) infected barley seedlings was investigated. It was found that with the progression of the disease, the infected leaves lost their ability to maintain a favourable water status. This was attributed to tears in the cuticle, which occurred from day 5 after infection. In addition, a decreasing responsiveness of leaf diffusion resistance to bulk leaf water content was observed, probably due to the increasing proportion of water loss via the tears in the cuticle. An increase in leaf dry weight per unit area which was not associated with an increase in tissue volume, was found in diseased leaves. These responses to infection were cumulative with disease development, with no sudden effect of sporulation. Leaf turgor and water potentials were found to be lower in diseased leaves than in control leaves.
Eamus, D. & Murray, M. 1991, 'Photosynthetic And Stomatal Conductance Responses Of Norway Spruce And Beech To Ozone, Acid Mist And Frost - A Conceptual-Model', Environmental Pollution, vol. 72, no. 1, pp. 23-44.
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Two-year-old beech and Norway spruce seedlings were exposed to a combination of ozone and acid mist treatments in open-top chambers in Scotland during the months of July through to September 1988. Replicate pairs of chambers received charcoal-filtered a
Berryman, C., Eamus, D. & Farrar, J. 1991, 'Variations In Epidermal-Cell Turgor Of Rust-Infected Barley Seedlings', New Phytologist, vol. 119, no. 4, pp. 535-540.
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Barley [Hordeum distichum (L.) Lam.] seedlings were infected with urediniospores of rust, Puccinia hordei Otth., 10 d after germination and the Zimmermann micro-pressure probe was used to measure the turgor potential of individual epidermal and palisade
Berryman, C., Eamus, D. & Farrar, J. 1991, 'The Hydraulic Conductivity Of Roots Of Rust-Infected Barley Seedlings', Physiological And Molecular Plant Pathology, vol. 38, no. 6, pp. 407-415.
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The influence of Puccinia hordei (rust) infection on the root hydraulic conductivity (Lp) of excised roots of Hordeum distichum cv. Maris Mink (barley) was investigated using the Scholander pressure chamber technique. The solute potential of the root exudate was also measured to determine the contribution of the osmotic component to the total driving force for water flow across the roots. The root Lp of infected plants was significantly lower than control plants on days 5, 6 and 7 after infection. On days 4 and 8 after infection, Lp did not differ significantly. Root Lp increased with time for both control and infected plants from days 5 to 8 after infection. Root Lp varied between 14 and 36 10-5 cm s-1 MPa-1 for roots of infected plants, and between 23 and 40 10-5 cm s-1 MPa-1 for control plants. The solute potential of root xylem sap exudate was significantly higher (less negative) than that of control sap on days 6, 7 and 8 after infection, reflecting a decrease in the transport of solutes into the root xylem of roots of diseased plants. In control and infected plants, as the applied pressure increased, solute potential root exudate increased. These results are discussed in relation to the known susceptibility of rust infected plants to drought and the mechanisms by which rust infection increases such susceptibility
Cape, J., Leith, I., Fowler, D., Murray, M., Sheppard, L., Eamus, D. & Wilson, R. 1991, 'Sulfate And Ammonium In Mist Impair The Frost Hardening Of Red Spruce Seedlings', New Phytologist, vol. 118, no. 1, pp. 119-126.
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Two-year-old seedlings of red spruce [Picea rubens Sarg. syn. P. rubra (Du Roi) Link] were grown in open-top chambers supplied with charcoal-filtered air near Edinburgh, Scotland. Between May and November 1988, plants were exposed to mists containing NH
Eamus, D. & Fowler, D. 1990, 'Photosynthetic And Stomatal Conductance Responses To Acid Mist Of Red Spruce Seedlings', Plant Cell And Environment, vol. 13, no. 4, pp. 349-357.
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Two-year-old seedlings of Picea rubens, growing in open-top chambers in Scotland were treated twice weekly from July 1987 to December 1987, with mist containing ammonium sulphate and nitric acid at a pH of either 2.5 or 5.0. The response of photosynthesis and stomatal conductance to light flux density and carbon dioxide concentration were measured in March 1989. Leaf chlorophyll a and b contents were also measured. Acid mist (pH 2.5) resulted in several significant changes. First, both the rate of light saturated photosynthesis (Amax) and CO2- saturated rate of photosynthesis (J) were substantially increased, when expressed per unit leaf area. Second, the apparent quantum yield and chlorophylls a and b content increased. Third, as a consequence of the greater chlorophyll content of the leaves treated with acid mist, the rate of Amax, and J, expressed per unit chlorophyll, was substantially reduced in pH 2.5 treated branches. Stomatal conductance was enhanced at all but the highest light flux densities, and was independent of the CO2 concentration, remaining high for all values of CO2 concentration used. These results show that acid mist caused a number of responses in the gas exchange and photosynthetic properties of red spruce.
Eamus, D. & Narayan, A. 1990, 'A pressure-volume analysis of Solanum-Melongena Leaves', Journal Of Experimental Botany, vol. 41, no. 6, pp. 661-668.
A pressure-volume analysis of aubergine (Solanum melongena) leaves following water stress was undertaken to determine a possible role of changes in cellular water relations in influencing stomatal conductance responses to water stress. A comparison of two methods of rehydrating the leaves was also undertaken. It was shown that the rehydration of excised leaves did not reveal osmoregulation, whilst rehydration of intact plants did reveal osmoregulation following water stress. An increase in the bulk volumetric elastic modulus and the bound water fraction also occurred in response to water stress. These results are discussed in relation to pressure-volume technique and stomatal conductance responses to drought
Barnes, J., Eamus, D. & Brown, K.R. 1990, 'The Influence Of Ozone, Acid Mist And Soil Nutrient Status On Norway Spruce [Picea-Abies (L) Karst] .2. Photosynthesis, Dark Respiration And Soluble Carbohydrates Of Trees During Late Autumn', New Phytologist, vol. 115, no. 1, pp. 149-156.
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Three-year old Norway spruce [Picea abies (L.) Karst.] trees of clonal stock originating from medium altitude in southern Germany were transplanted in May 1986 into two acid brown-earth soils which differed particularly in the amounts of exchangeable Ca2+ and Mg2+. During the summers of 1987 and 1988 trees were exposed in large-scale fumigation chambers (solardomes) to ozone at 200 or 40 (control) &micro;g m-3 Acid (pH 3?6) or control mist (pH 5?5) solution was applied daily to trees in each half of the solardomes. In late autumn (1988) the light response of CO2 exchange, and the chlorophyll and soluble carbohydrate contents of needles were determined. Ozone and/or acid mist treatment had only minor (< 10%) effects on the light-saturated rate of photosynthesis which were not statistically significant in plants from either soil. Needles from trees raised on the richer soil and exposed to a combination of ozone and acid mist showed a significant increase in the apparent quantum yield of photosynthesis which was associated with an increase in chlorophyll content. Ozone (alone) stimulated the rate of dark respiration by 40 and 58 % for trees grown in richer and poorer soils, respectively, and this was associated with a decrease in ethanol-soluble carbohydrate content of needles. Where significant interactions between ozone and acid mist were found, they were generally antagonistic. The reduction in the ethanol-soluble carbohydrates would be expected to reduce frost hardiness, and may contribute to the increased sensitivity of ozone-treated needles to freezing, which has been reported in previous studies.
Barnes, J., Eamus, D. & Brown, K.R. 1990, 'The Influence Of Ozone, Acid Mist And Soil Nutrient Status On Norway Spruce [Picea-Abies (L) Karst]', New Phytologist, vol. 114, no. 4, pp. 713-720.
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Three-year old Norway spruce [Picea abies (L.) Karst.] trees established from two clones (4076 and 2470) of a medium-altitude southern German provenance, were transplanted in May 1986 into two acid brown earth soils which differed particularly in the amounts of exchangeable Ca2+and Mg2+. During the summers of 1987 and 1988 trees were exposed in large-scale fumigation chambers (solardomes) to ozone at 200 or 40 &micro;g-3(control). Each day trees were treated with acid (pH 3-6) or control (pH 5-5) mist solution. In late autumn 1988 certain aspects of tree water relations were investigated. In clone 4076 ozone and acid mist reduced stomatal conductance in the light, but resulted in incomplete stomatal closure at night, reducing the diel range of stomatal conductance in treated trees grown on both soils. In addition, current year's needles excised from clone 4076 dried more rapidly following exposure to ozone and/or acid mist than needles from control trees, indicating impaired stomatal performance. However, evidence of both clonai and soil variation in this response was found. Cellular water relations of current year's shoots of clone 4076 were investigated using pressure-volume analysis. Exposure to ozone and/or acid mist resulted in a marked increase in the plasticity of tissues (reduction in ?) compared with controls, indicating that the pollutants induced cell wall loosening. In trees exposed to acid mist this was associated with lower cellular solute concentrations and a decrease in maximum turgor.
Barnes, J., Eamus, D., Davison, A.W., Ropoulsen, H. & Mortensen, L. 1990, 'Persistent Effects Of Ozone On Needle Water-Loss And Wettability In Norway Spruce', Environmental Pollution, vol. 63, no. 4, pp. 345-363.
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Four-year-old, seed-grown trees of Norway spruce (Picea abies (L.) Karst.) were exposed in open-top chambers to charcoal-filtered air (8 h daily mean 54 ?g O3 m-3) over three consecutive summers (19861988). In mid-May 1988, before the third season of fumigation and more than 7 months after exposure to ozone the previous summer had terminated, daily rates of transpiration from intact shoots and water loss from excised needles were measured together with the amount of wax on the needle surface. In mid-July, 92 days after the beginning of the third year of exposure, the wettability of needles was assessed by measuring the contact angle of water droplets on the surface of needles. Exposure to 156 ?g O3 m-3 resulted in a 16% increase in daily transpiration in current year's needles and a 28% increase in 1-year old needles. These effects were associated with slower stomatal closure in response to increasing water deficit in the needles previously exposed to 156 ?g m-3 ozone. The long-lasting nature of such ozone-induced effects could predispose trees to drought and winter desiccation. No significant effects of ozone were found on the amount of wax covering the needle surface, but a marked increase in the wettability of needles exposed to ozone was observed. The far reaching physiological consequences of these effects in the field and the possibility that similar disturbances may contribute to the decline of high-altitude forests of Norway spruce in Europe are discussed.
Eamus, D., Barnes, J., Mortensen, L., Ropoulsen, H. & Davison, A.W. 1990, 'Persistent Stimulation Of Co2 Assimilation And Stomatal Conductance By Summer Ozone Fumigation In Norway Spruce', Environmental Pollution, vol. 63, no. 4, pp. 365-379.
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CO2 assimilation rate, stomatal conductance and chlorophyll content of current and previous years' needles of Norway spruce were measured in May 1988, 205 days after the cessation of ozone fumigation during the summer of 1987. Rates of assimilation were consistently higher for both needle year age classes for ozone fumigated trees in comparison to control trees, although only statistically significant for part of the day for current year's needles. A 26% and 48% stimulation, overall, in mean daily rates of assimilation for current and previous years' needles of ozone fumigated trees was observed. This was due to an enhanced apparent quantum yield and light saturated rate of assimilation of ozone fumigated trees. The temperature response regression of assimilation versus temperature was also greater, such that at any given temperature, assimilation was higher for ozone treated trees than control trees. Stomatal conductance was greater for ozone fumigated trees than the controls, but this was only marginally statistically significant. Moreover, there was a consistent increase in chlorophyll content in both year classes in ozone-treated trees. These results are discussed in relation to a possible long term effect of ozone fumigation upon the processes of conifer winter hardening and spring de-hardening.
Barnes, J.D., Eamus, D. & Brown, K.A. 1990, 'The influence of ozone, acid mist and soil nutrient status on Norway spruce [Picea abies (L.) Karst.] I. Plant-water relations', New Phytologist, vol. 114, no. 4, pp. 713-720.
Three-year old Norway spruce established from 2 clones of a medium-altitude S Germany provenance were transplanted into 2 acid brown earth soil which differed particularly in the amounts of exchangeable Ca2+ and Mg2+. During summer trees were exposed in large-scale fumigation chambers to ozone at 200 or 40 g m-3 (control). Each day trees were treated with acid (pH 3.6) or control (pH 5.5) mist solution. In clone 4076 ozone and acid mist reduced stomatal conductance in the light, but resulted in incomplete stomatal closure at night, reducing the diel range of stomatal conductance in treated trees grown on both soils. Current year's needles excised from clone 4076 dried more rapidly following exposure to ozone and/or acid mist than needles from control trees, indicating impaired stomatal performance. However, evidence of both clonal and soil variation in this response was found. The pollutants induced cell wall loosening. In trees exposed to acid mist this was associated with lower cellular solute concentrations and a decrease in maximum turgor. Where interaction between ozone and acid mist were significant, they were always antagonistic. Effects of ozone and acid mist on stomata, which would be expected to enhance the sensitivity of trees to drought and winter desiccation, thus may be at least partially compensated for by concomitant changes in the turgor relations of individual cells. -from Authors
Eamus, D., Leith, I. & Fowler, D. 1989, 'The Influence Of Acid Mist Upon Transpiration, Shoot Water Potential And Pressure Volume Curves Of Red Spruce Seedlings', Annales Des Sciences Forestieres, vol. 46, pp. 577-580.
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Eamus, D., Leith, I. & Fowler, D. 1989, 'Water Relations Of Red Spruce Seedlings Treated With Acid Mist', Tree Physiology, vol. 5, no. 3, pp. 387-397.
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Pressurevolume curves, day and night transpiration rates, needle drying curves, and shoot water potentials were determined for 2-year-old red spruce trees that had been exposed for three months to a range of acid mists (pH 2.5 to pH 5.0) containing equimolar (NH4)2SO4 and HNO3. No effect of acid mist was observed on cuticular resistance or on the rates of day and night transpiration, although trees exposed to acid mist exhibited symptoms of mild water stress. Significant decreases in maximum turgor, the relative water content (RWC) associated with zero turgor, and bulk volumetric elastic modulus occurred as the pH of the mist decreased from 5.0 to 2.5. At all RWC values, there was an increase in solute potential as mist pH decreased. Shoot water potential declined with a decrease in pH of the mist.
Eamus, D., Barnes, J., Mortensen, L., Ropoulsen, H. & Davison, A.W. 1989, 'A Delayed-Effect Of Ozone Fumigation On Photosynthesis Of Norway Spruce', Annales Des Sciences Forestieres, vol. 46, pp. 568-572.
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Much of the research investigating the effects of gaseous pollutants upon plants has been concerned with dose-response relationships, particularly during the period of fumigation or in between the periods of fumigation, in the summer. However, there is increasing evidence that these pollutants increase plant susceptibility to winter injury (Barnes and Davison, 1988; Brown ef al., 1987). This is especially problematic for conifers, since they maintain needles and some metabolic activity throughout the winter. Indeed, there is increasing evidence that the forest decline documented for northeastern U.S.A. and Europe results from the interaction of various abiotic and biotic factors including air pollutants, frost and winter dessication (Brown et aL, 1987; Barnes and Davison, 1988).
Eamus, D. & Jarvis, P. 1989, 'The Direct Effects Of Increase In The Global Atmospheric Co2 Concentration On Natural And Commercial Temperate Trees And Forests', Advances In Ecological Research, vol. 19, pp. 1-55.
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Eamus, D. & Narayan, A. 1989, 'The Influence Of Prior Water-Stress And Abscisic-Acid Foliar Spraying On Stomatal Responses To Co2, Iaa, Aba, And Calcium In Leaves Of Solanum-Melongena', Journal Of Experimental Botany, vol. 40, no. 214, pp. 573-579.
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Eamus, D. 1987, 'Influence Of Preconditioning Upon The Changes In Leaf Conductance And Leaf Water Potential Of Soybean, Induced By Chilling, Water-Stress And Abscisic-Acid', Australian Journal Of Plant Physiology, vol. 14, no. 3, pp. 331-339.
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Eamus, D. 1987, 'Stomatal Behavior And Leaf Water Potential Of Chilled And Water-Stressed Solanum-Melongena, As Influenced By Growth History', Plant Cell And Environment, vol. 10, no. 8, pp. 649-654.
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Leaf diffusion resistance and leaf water potential of intact Solanum melongena plants were measured during a period of chilling at 6 &deg;C. Two pretreatments, consisting of a period of water stress or a foliar spraying of abscisic acid (ABA), were imposed upon the plants prior to chilling. The control plants did not receive a pretreatment. In addition to intact plant studies, stomatal responses to water loss and exogenous abscisic acid were investigated using excised leaves, and the influence of the pretreatment observed. Chilled, control plants wilted slowly and maintained open stomata despite a decline in leaf water potential to 2.2 MPa after 2 d of chilling. In contrast plants that had been water stressed or had been sprayed with abscisic acid, prior to chilling, did not wilt and maintained a higher leaf water potential and a greater leaf diffusion resistance. In plants that had not received a pretreatment, abscisic acid caused stomatal closure at 35 &deg;C, but at 6&deg;C it did not influence stomatal aperture. The two pretreatments greatly increased stomatal sensitivity to both exogenous ABA and water stress, at both temperatures. Stomatal response to water loss from excised leaves was greatly reduced at 6&deg;C. These results are discussed in relation to low temperature effects on stomata and the influence of preconditioning upon plant water relations.
Eamus, D. 1986, 'The Responses Of Leaf Water Potential And Leaf Diffusive Resistance To Abscisic-Acid, Water-Stress And Low-Temperature In Hibiscus-Esculentus - The Effect Of Water-Stress And Aba Pretreatments', Journal Of Experimental Botany, vol. 37, no. 12, pp. 1854-1862.
Intact plants of okra (Hibiscus esculentus) were chilled at 6&deg;C in the light, and leaf diffusion resistance (LDR) and leaf water potential measured. The response of the LDR of excised leaves to fresh weight loss and, separately, exogenous abscisic acid (ABA) supply, was also studied at 6&deg;C and 30&deg;C. The influence of two pre-treatments upon these measurements was studied. The two pre-treatments consisted of the imposition of a period of water stress at 30&deg;C prior to measurement (followed by re-watering) or the spraying of the leaves with ABA. It was found that plants that had been grown in a high humidity environment continuously (designated control plants) had stomata that were very unresponsive to both water loss from the leaves and to exogenous ABA at both temperatures (6&deg;C and 30&deg;C). Chilling the control plants resulted in rapid wilting and concomitant decline in leaf water potential. A pre-treatment of water stress prior to chilling did not alter or reduce the rate of development of chilling injury, nor did the pre-treatment increase the responsiveness of stomata at 6&deg;C to water loss or exogenous ABA. However, spraying the leaves with ABA prior to chilling reduced the severity and delayed the onset of chilling injury. Stomatal response to water stress and exogenous ABA was increased by the spraying pre-treatment. These results are discussed in relation to previous studies of the phenomenon of stomatal locking open at low temperature and the effect of pre-treatments upon the development of chill-resistance.
Eamus, D. 1986, 'Further Evidence In Support Of An Interactive Model In Stomatal Control', Journal Of Experimental Botany, vol. 37, no. 5, pp. 657-665.
The interaction between CO2 IAA, ABA, and temperature in the control of stomatal behaviour, was investigated in the chill-resistant Pisum sativum and chill-hardened Phaseolus vulgaris. It was found that the ability of kBA to induce stomatai closure was dependent upon the presence of CO2 in both species, at both temperatures (22 &deg;C, 5&deg;C) Similarly, the ability of IAA to decrease stomatal resistance, was dependent upon the presence of CO2 in both species, at both temperatures. Chilling at 5&deg;C in the light did not influence the response characteristics of stomata to CO2 ABA or IAA, in either species. These results are discussed in relation to a model of the interactions of these regulators of stomatal aperture.
Eamus, D. & Jennings, D. 1986, 'Turgor And Fungal Growth - Studies On Water Relations Of Mycelia Of Serpula-Lacrimans And Phallus-Impudicus', Transactions Of The British Mycological Society, vol. 86, pp. 527-535.
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The influence of substratum water potential on the growth of Serpula lacrimans and Phallus impudicus was investigated. Two methods of adjusting the water potential of the substratum were used; both gave qualitatively similar results. Linear growth rate decreased with substratum water potential. The turgor potential at the mycelial front and linear growth rate were positively correlated in both species on both media. An experiment concerned with growth from a medium of high water potential to one of lower water potential and vice versa produced results consistent with those obtained for growth on a single medium.
EAMUS, D. 1986, 'FURTHER EVIDENCE IN SUPPORT OF AN INTERACTIVE MODEL IN STOMATAL CONTROL', JOURNAL OF EXPERIMENTAL BOTANY, vol. 37, no. 178, pp. 657-665.
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Eamus, D., Thompson, W., Cairney, J.W.G. & Jennings, D.H. 1985, 'Internal structure and hydraulic conductivity of basidiomycete translocating organs', Journal of Experimental Botany, vol. 36, no. 7, pp. 1110-1116.
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Eamus, D., Thompson, W., Cairney, J. W. G. and Jennings, D. H. 1985. Internal structure and hydraulic conductivity of basidiomycete translocating organs.-J. exp. Bot. 36: 1110-1116.The presence in rhizomorphs of Armillaria mellea and cords of Phallus impudicus of wide diameter hyphae (5-20 m), which run for considerable distances along these linear organs, has been demonstrated. The longitudinal hydraulic conductivity of these organs has been determined experimentally and similar values were obtained when the hydraulic conductivity was calculated theoretically on the basis that the vessel hyphae were the sole channel for water movement along these organs. The experimental data have been discussed in relation to other data for long-distance translocation in basidiomycete linear organs. It is concluded that the vessel hyphae are the main channels for turgor-driven translocation. &copy; 1985 Oxford University Press.
Eamus, D. & Wilson, J.M. 1984, 'The effect of chilling temperatures on the water relation of leaf epidermal cells of Rhoeo discolor', Plant Science Letters, vol. 37, no. 1-2, pp. 101-104.
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Cell turgor pressure, volumetric elastic modulus ({lunate}) and hydraulic conductivity (Lp) of the lower epidermal cells of the chill sensitive plant Rhoeo discolor (Commelinaceae) were measured at different temperatures between 7 and 24&deg;C with a micro pressure-probe. Chilling at a rate of 1&deg;C/2 min caused a small, gradual decrease in cell turgor, but turgor rapidly increased to the control level after 90 min at 8&deg;C. In addition, chilling caused a decrease in Lp but did not influence {lunate}. In cells chilled at 7&deg;C there was an increase of relaxation half time which corresponded to a decreasing Lp. &copy; 1984.
Eamus, D. & Jennings, D.H. 1984, 'Determination of water, solute and turgor potentials of mycelium of various basidiomycete fungi causing wood decay', Journal of Experimental Botany, vol. 35, no. 12, pp. 1782-1786.
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Using thermocouple psychrometry, the water, solute and turgor potentials of hyphae of Phallus impudicus and Serpula lacrimans, cords of P. impudicus, Phanerochaete velutina and S. lacrimans and rhizomorphs of Armillaria mellea were determined. A comparison was made between laboratory- and field-grown cords of P. impudicus and P. velutina. Comparison was made also between the water relations of the hyphae at the growing front, and hyphae of the more distal, basal regions. Similarly, the growing regions of cords/rhizomorphs were compared with the older, non-extending basal regions of the same structures. In all cases gradients of water and turgor potentials were found from basal, older regions to younger, extending regions. These results are discussed in relation to the mechanism of translocation in fungi. &copy; 1984 Oxford University Press.
Eamus, D. & Wilson, J.M. 1984, 'A model for the interaction of low temperature, ABA, IAA, and CO2 in the control of stomatal behaviour', Journal of Experimental Botany, vol. 35, no. 1, pp. 91-98.
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In the chilling sensitive (C.S.) species Phaseolus vulgaris it was found that at 22 &deg;C ABA induced stomatal closure but this effect was dependent on the presence of CO2. In the absence of CO2 the effect of ABA was completely lost. In contrast to ABA, the effect of IAA at 22 &deg;C was to increase stomatal opening as the IAA concentration increased from 10-2 to 10 mol m-3, and this effect was dependent upon the presence of CO2. However, at 5 &deg;C the action of ABA was reversed and it was found to induce stomatal opening when fed via the transpiration stream in excised leaves. Similarly, the CO2 response characteristics were reversed at low temperatures as removal of CO2 from the atmosphere caused stomatal closure. However, the effect of IAA at 5 &deg;C in the presence of CO2 and with or without ABA was to increase stomatal aperture with increasing IAA concentration. Significantly, ABA was found to have no effect upon aperture in the presence of CO2 when IAA was added. The interactive effects of ABA, IAA, CO2 and low temperature are discussed in relation to a model proposed by the authors. &copy; 1984 Oxford University Press.
Eamus, D. & Tomos, A.D. 1983, 'The influence of abscisic acid on the water relations of leaf epidermal cells of Rhoeo discolor', Plant Science Letters, vol. 31, no. 2-3, pp. 253-259.
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The water relations of individual Rhoeo discolor (Commelinaceae) leaf epidermal cells were measured using the micro pressure-probe. Cell turgor pressure, volumetric elastic modulus ({lunate}) and hydraulic conductivity (Lp) were determined. The influence of ABA on these parameters was studied by both immersion and vacuum infiltration of the leaf in 100 M abscisic acid (ABA) solution (containing 100 M dimethylsulphoxide (DMSO)). ABA treatment slightly, but significantly, raised the mean hydraulic conductivity of the cell membranes following both treatments. With infiltration the effect was immediate, with immersion the effect followed a lag period of about 4 h. ABA had no effect on cell turgor pressure or elastic modulus. In several cells in which a large number of individual Lp measurements were performed over a 30-min period a gradual increase of relaxation half time was observed, corresponding to a decreasing Lp. &copy; 1983.
Eamus, D., Fenton, R. & Wilson, J.M. 1983, 'Stomatal behaviour and water relations of chilled Phaseolus vulgaris L. and Pisum sativum L.', Journal of Experimental Botany, vol. 34, no. 4, pp. 434-441.
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Leaf diffusion resistance interpreted as stomatal resistance, leaf water potential (w), solute potential (s) and leaf turgor potential (p) of the chilling sensitive species Phaseolus vulgaris were determined during chilling at 4 &deg;C in the light. Both chill-hardened and non-hardened plants were used. For comparison, the chilling resistant species Pisum sativum was also used.The results for chilled P. sativum were similar to those obtained for chill-hardened P. vulgaris plants receiving a chilling treatment. In both cases a reduction in stomatal aperture and the maintenance of a positive leaf turgor were the responses to chilling. Leaves of chilled but non-hardened P. vulgaris plants were found to maintain open stomata throughout the chilling treatment despite a severe wilt developing after 7 h at 4 &deg;C. This was in contrast to the chill-resistant P. sativum. which showed a rapid closing and subsequent re-opening of the stomata to a new reduced aperture.During the first 12 h of chilling wof P. vulgaris leaves changed from -0.47 MPa to -1.24 MPa. On more prolonged chilling w tended to return to pre-chilling values. In addition. p decreased from 0.42 MPa to zero after only 9 h of chilling, and remained at this value for the remainder of the chilling period, s, changed rapidly from -0.89 MPa to -1.35 MPa in the first 7.5 h, and after 9 h. w and s, were equal, i.e. zero p. In contrast, the chilling resistant plant P. sativum maintained a positive p throughout the chilling period, and there was little difference between values of w, and s in control and chilled leaves. &copy; 1983 Oxford University Press.
Eamus, D. & Wilson, J.M. 1983, 'ABA levels and effects in chilled and hardened Phaseolus vulgaris', Journal of Experimental Botany, vol. 34, no. 8, pp. 1000-1006.
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Leaf abscisic acid (ABA) levels of chilled P. vulgaris were measured after 18 h chilling at 5&deg;C, at a saturation deficit of 1.24 g m-3 (SD), and after chilling in a water-saturated atmosphere. Changes were also followed during a chill hardening period of 4 d at 12&deg;C, 2.1 g m-3 SD. It was found that hardening resulted in an almost 5. fold increase in ABA levels after 3 d at 12&deg;C, and this decreased to approximately control levels on the fourth day. Subsequent chilling of hardened plants produced no change in ABA levels from that of control plants (22&deg; C). In contrast, non-hardened plants chilled at 1.24 g m-3 SD had ABA levels almost 3 times the level of control plants. However, chilling in a water-saturated atmosphere resulted in a decrease in ABA levels.In addition, the response of leaf diffusion resistance (LDR) to exogenous ABA fed via the transpiration stream was measured at 5 &deg; C and 22&deg; C in hardened and non-hardened plants. Use of tritium-labelled ABA was made to calculate the stomatal sensitivity to ABA. It was found that exogenous ABA caused an increased in LDR at 22&deg;C in both hardened and non-hardened plants. However, the sensitivity of the hardened plants to ABA was greater in terms of rate of closure and amount of ABA required to close the stomata. At 5&deg;C, however, ABA caused stomatal opening and the maintainance of open stomata in non-hardened plants. In hardened plants, ABA caused stomatal closure at 5&deg;C. These results are discussed in relation to the locking-open response of chilled P. vulgaris stomata. &copy; 1983 Oxford University Press.

Reports

Eamus, D. Land and Water Australia 2009, Identifying groundwater dependent ecosystems, pp. 1-14, Canberra, Australia.
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Groundwater dependent ecosystems (GDEs) are important elements in the landscape that require access to groundwater to maintain their health and vigour. They are important because of their conservation, biodiversity, ecological, social and economic value. There are two threats to GDEs outright loss of habitat and outright loss of groundwater resources.
Eamus, D. Land and Water Australia 2009, Impacts of plantation age and fire and disturbance on catchment water yield, pp. 1-9, Canberra, Australia.
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The problem of sustainable water resource management is a key issue confronting Australia in the 21st century. Increasing demand through increased population size, declining rainfall across parts of temperate Australia and consequently an increasing need to allocate water to maintain ecosystem health and ecosystem service provision are the dominant threats to the maintenance of an adequate supply of water to urban, peri-urban and rural communities.
Macinnis-Ng, C.M. & Eamus, D. Land and Water Australia 2009, Climate change and water use of native vegetation, pp. 1-16, Canberra, Australia.
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Under climate change conditions Australia will generally be hotter and, for many parts of the country drier. Vegetation water use is strongly influenced by soil moisture availability (which is influenced by rainfall) and evaporative demand. Soil moisture will be more scarce in the future across much of the continent due to declining rainfall. The major input of water into the Australian landscape is rainfall and most rainfall (7095%) returns to the atmosphere as evapotranspiration, leaving little water for human consumption, riverflows and recharge of groundwater. The proportion of rainfall used in evapotranspiration increases as rainfall declines so even though the absolute amount of transpiration may decline, the water yield of a landscape will also decline as rainfall decreases with climate change.
Macinnis-Ng, C.M. & Eamus, D. Land & Water Australia 2009, Carbon uptake and water use of vegetation, pp. 1-15, Canberra, Australia.
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Accumulation and storage of carbon in trees is one method of sequestration which may help offset increasing atmospheric CO2 concentrations. However, for every molecule of CO2 absorbed by a leaf, up to a thousand molecules of water are released as transpiration, water that has moved out of the soil into the atmosphere. Therefore, simply planting more trees to absorb more CO2 is not as risk-free as may originally be thought, especially in the dry continent that is Australia. The location for planting trees is also an important factor when considering their impact on water supplies. Trees use more water than grasses and shrubs and the productivity of trees is strongly influenced by water availability. Sites with more rainfall have faster rates of carbon accumulation and store more carbon. Whether trees should be planted in groundwater discharge zones or recharge zones is an important consideration when planting trees. Water use of a stand of trees changes as it ages. The period of greatest water use coincides with the period of most rapid carbon accumulation.Water is a scarce resource in Australia so any climate mitigation schemes involving reforestation must also consider the environmental, social and economic cost of water used by the new plantation
Whitley, R.J. & Eamus, D. Land and Water Australia 2009, How much water does a woodland or plantation use: a review os some measurement methods, pp. 1-17, Canberra, Australia.
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Determining the water balance of a landscape is important to sustainable management of water, vegetation and land resources. Water flow through vegetation is the principle pathway for the discharge of water from Australian landscapes. The rate of this discharge is determined by solar radiation, leaf area index, vapour pressure deficit and soil moisture content. Tree transpiration from plantations and native woodlands and forests is an important determinant of the water balance of much of the Australian landscape. Several field-based methods of measuring tree and landscape water use, including sapflow techniques, eddy covariance and scintillometery are briefly discussed
Macinnis-Ng, C.M. & Eamus, D. Land and Water Australia 2009, The increasing density of shrubs and trees across a landscape, pp. 1-16, Canberra, Australia.
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Woody thickening is a global phenomenon whereby the density of trees and woody shrubs is increasing in the landscape. Although most commonly seen in arid and semi-arid landscapes, it also occurs in other environments. This process has a number of impacts on landscape function. Woody thickening can be a naturally occurring phenomenon but is being enhanced by climate change, changes in fire regimes and other human land use activity. Woody thickening influences carbon storage and carbon accounting by increasing the biomass present in a landscape. Water balances are impacted through increases in evapotranspiration, which leaves less water available for stream flow. Nitrogen cycling is also affected. Furthermore, reduced grass growth results in less food production for livestock. Woody thickening may play a role in ameliorating salinisation of soil and groundwater by preventing rises in water tables.
Yunusa, I.A., Veeragathipillai, M., Burchett, M., Eamus, D. & Skilbeck, G. Not applicable 2008, Utilisation of Coal Ash in Horticultural and Agricultural Ecosystems, pp. 1-111, Sydney, Australia.