Science Partnerships Liaison, Terrestrial Ecosystem Research Network (TERN); Science Director, TERN OzFlux
Dr James Cleverly has a research background in plant ecophysiology, ecohydrology, soil science, micrometeorology, and climatology. As a member of the Terrestrial Ecohydrology Research Group led by Professor Derek Eamus, James is currently focused on dryland soil-vegetation-atmosphere interactions in central Australia, on groundwater-vegetation interactions in the Hunter Valley and on mortality at physiological and ecological scales.
James PhD research at the the University of Nevada Las Vegas focused on the leaf-level physiology of riparian vegetation. Transpiration and evaporation at multiple scales (leaf, whole plant and ecosystem) are important because of the critical issues of water budget and supply for communities and ecosystems in the arid regions of the southwestern U.S. Dr Cleverly's interest in groundwater–vegetation interactions continued in New Mexico USA through the micrometeorological study of evapotranspiration and energy balance along the Rio Grande. It was at this time that James participated as an expert witness in plant water use for the U.S. Supreme Court (i.e., the High Court), where he developed his research interests in ecohydrology.
While at UTS, Dr Cleverly has expanded his research interests into the study of ecosystem carbon dynamics and productivity, and how climate and precipitation impact these dynamics in semi-arid regions. This research is of particular global importance because of the impact of productivity in the Southern Hemisphere, and especially in Australia, on fluctuations in the global carbon cycle.
American Geophysical Union
American Meteorology Society
Australian Meteorological & Oceanographic Society
European Geophysical Union
PUBLICATIONS NOT LISTED ELSEWHERE:
J.R. Cleverly and G. Dello Russo (2007). Salt cedar control: Exotic species in the San Acacia reach. Water resouces of the Middle Rio Grande. L.G. Price, P.S. Johnson and D. Bland. Socorro, NM, New Mexico Bureau of Geology and Mineral Resources: 76-79.
Eichinger, D.I. Cooper, J.L. Hatfield, S. Bawazir and W.P. Kustas. 2002. Turbulence spectra over open water during a thunderstorm outflow event. Proceedings: American Meteorological Society 25th Agricultural and Forest Meteorology Meeting, Norfolk, VA, 20-24.
Thibault, J., C. Dahm and J.R. Cleverly. 2001. Quantifying riparian evapotranspiration. New Mexico Water Dialogue. March: 3–8
Bonan, G., J.R. Cleverly and J. Shen 1996. Land surface process modeling. In Colloquium on Terrestrial Ecosystems and the Atmosphere Eds. R. Monson and D. Schimel. National Center for Atmospheric Research, Boulder, CO.
Smith, S.D., A. Sala, D.A. Devitt and J.R. Cleverly 1995. Evapotranspiration from a saltcedar-dominated desert floodplain: a scaling approach. In Symposium on shrubland ecosystem dynamics in a changing climate Eds. J.R. Barrow, E.D. McArthur, R.E. Sosebee and R.J. Tausch. Department of Agriculture, Forest Service, Intermountain Research Station, Las Cruces, NM, pp. 199-204.
Can supervise: YES
- Carbon, water and energy fluxes of arid-land Acacia swales
- Physics of the atmospheric surface layer and interactions with terrestrial ecosystems
- Eco-hydrology of Groundwater Dependent Ecosystems
91270 Plant Physiology and Ecophysiology
OzFlux workshop annual short course on:
- ecosystem carbon, water and energy cycles
- statistics and time series analysis
- eddy covariance theory
- boundary-layer meteorology
- network data analysis standards
Bloomfield, KJ, Prentice, IC, Cernusak, LA, Eamus, D, Medlyn, BE, Rumman, R, Wright, IJ, Boer, MM, Cale, P, Cleverly, J, Egerton, JJG, Ellsworth, DS, Evans, BJ, Hayes, LS, Hutchinson, MF, Liddell, MJ, Macfarlane, C, Meyer, WS, Togashi, HF, Wardlaw, T, Zhu, L & Atkin, OK 2019, 'The validity of optimal leaf traits modelled on environmental conditions.', New Phytologist, vol. 221, no. 3, pp. 1409-1423.View/Download from: UTS OPUS or Publisher's site
The ratio of leaf intercellular to ambient CO2 (χ) is modulated by stomatal conductance (gs ). These quantities link carbon (C) assimilation with transpiration, and along with photosynthetic capacities (Vcmax and Jmax ) are required to model terrestrial C uptake. We use optimization criteria based on the growth environment to generate predicted values of photosynthetic and water-use efficiency traits and test these against a unique dataset. Leaf gas-exchange parameters and carbon isotope discrimination were analysed in relation to local climate across a continental network of study sites. Sun-exposed leaves of 50 species at seven sites were measured in contrasting seasons. Values of χ predicted from growth temperature and vapour pressure deficit were closely correlated to ratios derived from C isotope (δ13 C) measurements. Correlations were stronger in the growing season. Predicted values of photosynthetic traits, including carboxylation capacity (Vcmax ), derived from δ13 C, growth temperature and solar radiation, showed meaningful agreement with inferred values derived from gas-exchange measurements. Between-site differences in water-use efficiency were, however, only weakly linked to the plant's growth environment and did not show seasonal variation. These results support the general hypothesis that many key parameters required by Earth system models are adaptive and predictable from plants' growth environments.
Cleverly, J, Eamus, D, Edwards, W, Grant, M, Grundy, MJ, Held, A, Karan, M, Lowe, AJ, Prober, SM, Sparrow, B & Morris, B 2019, 'TERN, Australia's Land Observatory: addressing the global challenge of forecasting ecosystem responses to climate variability and change', Environmental Research Letters.View/Download from: UTS OPUS or Publisher's site
The global challenge of understanding and forecasting ecosystem responses to climate extremes and climate change is addressed in this review of research enabled through environmental research infrastructure (RI) provided by Australia's Terrestrial Ecosystem Research Network (TERN). Two primary climatic drivers of ecosystem structure and function in Australia are fire and aridity, to which Australian flora and fauna has shown marked adaptability. Australian vegetation shows resilience to climate extremes of flooding rains, droughts and heatwaves such that variability in primary productivity of Australian vegetation has a tangible effect on the global carbon cycle. Nonetheless, Australian flora and ecosystems could be vulnerable to projected climate change (e.g., to increasing vapour pressure deficit). Refugia are also vulnerable to climate change, with conditions in these areas already near the tipping point for a change in community composition. Ensuring genetic diversity during directional change in climate (e.g., increasing aridity) requires proactive approaches to conservation and restoration projects. To address these challenges, TERN provides environmental research infrastructure (RI) at three scales of observation: i) environmental monitoring using remote sensing techniques at a landscape and continental scale; ii) a spatially extensive network of ecosystem monitoring plots; and iii) intensely measured sites collecting detailed data on ecosystem processes. Through partnerships with international environmental RIs, TERN enables research that addresses global challenges, on the first steps toward the forecasting of ecosystem–climate interactions.
Li, B, Huang, F, Chang, S & Sun, N 2019, 'The Variations of Satellite-Based Ecosystem Water Use and Carbon Use Efficiency and Their Linkages with Climate and Human Drivers in the Songnen Plain, China', Advances in Meteorology, vol. 2019, pp. 1-15.View/Download from: Publisher's site
Ecosystem water use efficiency (WUE) and carbon use efficiency (CUE), as two of the most important ecological indicators of an ecosystem, represent the carbon assimilation rate of unit water consumption and the capacity of transferring carbon from the atmosphere to potential carbon sinks. Revealing WUE and CUE changes and their impact factors is vital for regional carbon-water interactions and carbon budget assessment. Climate affects carbon and water processes differently. Compared to WUE, the variations in CUE in response to climate factors and human activity remain inadequately understood. In this study, ecosystem-level WUE and CUE variations in the Songnen Plain (SNP), Northeast China, during 2001–2015, were investigated using Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data. The relationships between WUE, CUE, main climate factors, and human impacts were explored. The results showed that ecosystem WUE and CUE have fluctuated over time, with regional average values of 1.319 gC·kg−1H2O and 0.516, respectively. Deciduous broad-leaved forests had the highest average WUE but the lowest CUE. The multiyear average CUE of grassland ranked in first place, while the lowest WUE indicated that a lesser capacity of net productivity was generated by the use of limited water supply. WUE and CUE showed a downward trend in most areas of the SNP, indicating that the carbon sequestration capacity of the terrestrial ecosystem became weaker in the past 15 years. Annual precipitation and relative humidity had positive influences on WUE and CUE in more than 60% of the study area. The total annual sunshine duration and annual average temperature negatively affected WUE and CUE in most areas. Human activities had a positive effect on ecosystem WUE changes in the SNP but might inhibit CUE variations. Our findings aid in understanding the biological regulation mechanisms of carbon-water cycle coupling and provide a ...
Liu, S, Su, H, Zhang, R, Tian, J, Chen, S, Wang, W, Yang, L & Liang, H 2019, 'Based on the Gaussian Fitting Method to Derive Daily Evapotranspiration from Remotely Sensed Instantaneous Evapotranspiration', Advances in Meteorology, vol. 2019, pp. 1-13.View/Download from: Publisher's site
Evapotranspiration (ET) is a significant component in the water cycle, and the estimation of it is imperative in water resource management. Regional ET can be derived by using remote sensing technology which combines remote sensing inputs with ground-based measurements. However, instantaneous ET values estimated through remote sensing directly need to be converted into daily totals. In this study, we attempted to retrieve daily ET from remotely sensed instantaneous ET. The study found that the Gaussian fitting curve closely followed the ET measurements during the daytime and hence put forward the Gaussian fitting method to convert the remotely sensed instantaneous ET into daily ETs. The method was applied to the middle reaches of Heihe River in China. Daily ETs on four days were derived and evaluated with ET measurements from the eddy covariance (EC) system. The correlation between daily ET estimates and measurements showed high accuracy, with a coefficient of determination (R2) of 0.82, a mean average error (MAE) of 0.41 mm, and a root mean square error (RMSE) of 0.46 mm. To make more scientific assessments, percent errors were calculated on the estimation accuracy, which ranged from 0% to 18%, with more than 80% of locations having the percent errors within 10%. Analyses on the relationship between daily ET estimates and land use status were also made to assess the Gaussian fitting method, and the results showed that the spatial distribution of daily ET estimates well demonstrated ET differences caused by land use types and was intimately linked with the vegetation pattern. The comparison between the Gaussian fitting method and the sine function method and the ETrF method indicated that results derived through the Gaussian fitting method had higher precision than that obtained by the sine function method and the ETrF method.
Wang, C, Beringer, J, Hutley, LB, Cleverly, J, Li, J, Liu, Q & Sun, Y 2019, 'Phenology dynamics of dryland ecosystems along North Australian Tropical Transect revealed by satellite solar-induced chlorophyll fluorescence', Geophysical Research Letters, vol. 46, no. 10, pp. 5294-5302.View/Download from: UTS OPUS or Publisher's site
Accurate phenological characterization of dryland ecosystems has remained a challenge due to the complex composition of plant functional types, each having distinct phenological dynamics, sensitivity to climate and disturbance. Solar-induced chlorophyll fluorescence (SIF), a proxy for photosynthesis, offers potential to alleviate such challenge. We here explore this potential using dryland systems along the North Australian Tropical Transect (NATT) with SIF derived from Orbiting Carbon Observatory-2. SIF identified the seasonal onset and senescence of Gross Primary Production at eddy covariance sites with improved accuracy over Enhanced Vegetation Index (EVI) and Near Infrared Reflectance of terrestrial Vegetation (NIRv) from Moderate Resolution Imaging Spectroradiometer, especially at inland xeric shrublands. At regional scale, SIF depicted both earlier onset and senescence across NATT. We hypothesized that SIF outperformed EVI and NIRv mainly because, unlike reflectance, it is not contaminated by background soil and its total signal is contributed by mixed plant species in additive way.
Xie, Z, Huete, A, Cleverly, J, Phinn, S, McDonald-Madden, E, Cao, Y & Qin, F 2019, 'Multi-climate mode interactions drive hydrological and vegetation responses to hydroclimatic extremes in Australia', Remote Sensing of Environment, vol. 231.View/Download from: Publisher's site
© 2019 Australia has experienced a large frequency of hydroclimatic events since the early 21st century, with multiple large-scale droughts and flooding rains exerting dramatic impacts on water resources and ecosystems. Despite these pronounced consequences, the coupling of ecosystem functioning to extreme climate variability remains elusive due to the lack of complete understanding of hydrological connections. In this study, we investigated the spatiotemporal trends of Australia's hydrological and vegetation responses to three climate modes: El Niño-Southern Oscillation, the Indian Ocean dipole and the Southern Annular Mode, utilizing climate indices, satellite-derived total water storage anomaly (TWSA) from GRACE, precipitation from TRMM and vegetation greenness from MODIS. Using partial cross-correlation and vegetation sensitivity analyses to interpret the interactions among climate modes, water resources and vegetation across Australia, three hydroclimatic extreme events from 2002 to 2017 were analyzed: (i) a prolonged drought (2002–09, colloquially known as the 'big dry'); (ii) a dramatic wet pulse (2010–11, the 'big wet'); and (iii) another anomalous El Niño event (2015). Our results showed the entire continent partitioned into three geographic zones with diverse drying and wetting trends in total water storage, precipitation and vegetation greenness, reflecting varying and fundamental influences from the individual climate modes. Ecosystem productivity was found to be better related and more sensitive to TWSA than precipitation across different hydroclimate zones and during both extreme dry and wet conditions. We also observed TWSA increased rapidly during wet extremes, and these gains in water resources persisted for an additional four years (i.e., TWSA remained positive until 2015 following the 2011 'big wet'). Lastly, findings from another hydroclimatic event (the 2015 El Niño drought) further confirmed the relationships among climate, water and ecosyst...
Bloomfield, KJ, Cernusak, LA, Eamus, D, Ellsworth, DS, Prentice, IC, Wright, IJ, Boer, MM, Bradford, MG, Cale, P, Cleverly, J, Egerton, JG, Evans, BJ, Hayes, L, Hutchinson, MF, Liddell, MJ, Macfarlane, C, Meyer, WS, Prober, S, Togashi, HF, Wardlaw, T, Zhu, L & Atkin, OK 2018, 'A continental-scale assessment of variability in leaf traits: within species, across sites and between seasons', Functional Ecology, vol. 32, no. 6, pp. 1492-1506.View/Download from: UTS OPUS or Publisher's site
1. Plant species show considerable leaf trait variability that should be accounted for
in dynamic global vegetation models (DGVMs). In particular, differences in the acclimation
of leaf traits during periods more and less favourable to growth have
rarely been examined.
2. We conducted a field study of leaf trait variation at seven sites spanning a range
of climates and latitudes across the Australian continent; 80 native plant species
were included. We measured key traits associated with leaf structure, chemistry
and metabolism during the favourable and unfavourable growing seasons.
3. Leaf traits differed widely in the degree of seasonal variation displayed. Leaf mass
per unit area (Ma) showed none. At the other extreme, seasonal variation accounted
for nearly a third of total variability in dark respiration (Rdark).
4. At the non-tropical sites, carboxylation capacity (Vcmax) at the prevailing growth
temperature was typically higher in summer than in winter. When Vcmax was normalized
to a common reference temperature (25°C), however, the opposite pattern
was observed for about 30% of the species. This suggests that metabolic
acclimation is possible, but far from universal.
Li, L, Wang, YP, Eamus, D, Yu, Q, Huete, A, Cleverly, J, Shi, H, Cheng, L & Zhang, L 2018, 'Evaluating global land surface models in CMIP5: analysis of ecosystem water- and light-use efficiences, and rainfall partitioning', Journal of Climate, vol. 31, no. 8, pp. 2995-3008.View/Download from: UTS OPUS or Publisher's site
Li, Y, Shi, H, Zhou, L, Eamus, D, Huete, A, Li, L, Cleverly, J, Hu, Z, Harahap, M, Yu, Q, He, L & Wang, S 2018, 'Disentangling Climate and LAI Effects on Seasonal Variability in Water Use Efficiency Across Terrestrial Ecosystems in China', Journal of Geophysical Research: Biogeosciences, vol. 123, no. 8, pp. 2429-2443.View/Download from: UTS OPUS or Publisher's site
©2018. American Geophysical Union. All Rights Reserved. Water use efficiency (WUE), the ratio of gross primary productivity (GPP) over evapotranspiration (ET), is a critical ecosystem function. However, it is difficult to distinguish the individual effects of climatic variables and leaf area index (LAI) on WUE, mainly due to the high collinearity among these factors. Here we proposed a partial least squares regression-based sensitivity algorithm to confront the issue, which was first verified at seven ChinaFlux sites and then applied across China. The results showed that across all biomes in China, monthly GPP (0.42–0.65), ET (0.33–0.56), and WUE (0.01–0.31) showed positive sensitivities to air temperature, particularly in croplands in northeast China and forests in southwest China. Radiation exerted stronger effects on ET (0.55–0.78) than GPP (0.19–0.65), resulting in negative responses (−0.44 to 0.04) of WUE to increased radiation among most biomes. Increasing precipitation stimulated both GPP (0.06–0.17) and ET (0.05–0.12) at the biome level, but spatially negative effects of excessive precipitation were also found in some grasslands. Both monthly GPP (−0.01 to 0.29) and ET (0.02–0.12) showed weak or moderate responses to vapor pressure deficit among biomes, resulting in weak response of monthly WUE to vapor pressure deficit (−0.04 to 0.08). LAI showed positive effects on GPP (0.18–0.60), ET (0–0.23), and WUE (0.13–0.42) across biomes, particularly on WUE in grasslands (0.42 ± 0.30). Our results highlighted the importance of LAI in influencing WUE against climatic variables. Furthermore, the sensitivity algorithm can be used to inform the design of manipulative experiments and compare with factorial simulations for discerning effects of various variables on ecosystem functions.
Luo, Q, O'Leary, G, Cleverly, J & Eamus, D 2018, 'Effectiveness of time of sowing and cultivar choice for managing climate change: wheat crop phenology and water use efficiency', International Journal of Biometeorology, vol. 62, no. 6.View/Download from: UTS OPUS or Publisher's site
Mallick, K, Toivonen, E, Trebs, I, Boegh, E, Cleverly, J, Eamus, D, Koivusalo, H, Drewry, D, Arndt, SK, Griebel, A, Beringer, J & Garcia, M 2018, 'Bridging Thermal Infrared Sensing and Physically-Based Evapotranspiration Modeling: From Theoretical Implementation to Validation Across an Aridity Gradient in Australian Ecosystems', Water Resources Research, vol. 54, no. 5, pp. 3409-3435.View/Download from: UTS OPUS or Publisher's site
© 2018. The Authors. Thermal infrared sensing of evapotranspiration (E) through surface energy balance (SEB) models is challenging due to uncertainties in determining the aerodynamic conductance (gA) and due to inequalities between radiometric (TR) and aerodynamic temperatures (T0). We evaluated a novel analytical model, the Surface Temperature Initiated Closure (STIC1.2), that physically integrates TRobservations into a combined Penman-Monteith Shuttleworth-Wallace (PM-SW) framework for directly estimating E, and overcoming the uncertainties associated with T0and gAdetermination. An evaluation of STIC1.2 against high temporal frequency SEB flux measurements across an aridity gradient in Australia revealed a systematic error of 10–52% in E from mesic to arid ecosystem, and low systematic error in sensible heat fluxes (H) (12–25%) in all ecosystems. Uncertainty in TRversus moisture availability relationship, stationarity assumption in surface emissivity, and SEB closure corrections in E were predominantly responsible for systematic E errors in arid and semi-arid ecosystems. A discrete correlation (r) of the model errors with observed soil moisture variance (r = 0.33–0.43), evaporative index (r = 0.77–0.90), and climatological dryness (r = 0.60–0.77) explained a strong association between ecohydrological extremes and TRin determining the error structure of STIC1.2 predicted fluxes. Being independent of any leaf-scale biophysical parameterization, the model might be an important value addition in working group (WG2) of the Australian Energy and Water Exchange (OzEWEX) research initiative which focuses on observations to evaluate and compare biophysical models of energy and water cycle components.
Nolan, R, Tarin, T, Rumman, R, Cleverly, J, Fairweather, KA, Zolfaghar, S, Santini, NS, O'Grady, AP & Eamus, D 2018, 'Contrasting ecophysiology of two widespread arid zone tree species with differing access to water resources', Journal of Arid Environments, vol. 153, pp. 1-10.View/Download from: UTS OPUS or Publisher's site
Rumman, R, Cleverly, J, Nolan, RH, Tarin, T & Eamus, D 2018, 'Speculations on the application of foliar <sup>13</sup>C discrimination to reveal groundwater dependency of vegetation, provide estimates of root depth and rates of groundwater use', Hydrology and Earth System Sciences Discussions, vol. 22, pp. 1-25.View/Download from: UTS OPUS or Publisher's site
Rumman, R, Cleverly, J, Nolan, RH, Tarin, T & Eamus, D 2018, 'Speculations on the application of foliar 13C discrimination to reveal groundwater dependency of vegetation and provide estimates of root depth and rates of groundwater use', Hydrology and Earth System Sciences, vol. 22, no. 9, pp. 4875-4889.View/Download from: UTS OPUS or Publisher's site
© Author(s) 2018. Groundwater-dependent vegetation is globally distributed, having important ecological, social, and economic value. Along with the groundwater resources upon which it depends, this vegetation is under increasing threat through excessive rates of groundwater extraction. In this study we examined one shallow-rooted and two deep-rooted tree species at multiple sites along a naturally occurring gradient in depth-to-groundwater. We measured (i) stable isotope ratios of leaves (δ 13C), xylem, and groundwater (δ 2H and δ 18O); and (ii) leaf-vein density. We established that foliar discrimination of 13C (Δ13C) is a reliable indicator of groundwater use by vegetation and can also be used to estimate rooting depth. Through comparison with a continental-scale assessment of foliar Δ13C, we also estimated the upper limits to annual rates of groundwater use. We conclude that maximum rooting depth for both deep-rooted species ranged between 9.4 and 11.2 m and that annual rates of groundwater use ranged from ca. 1400 to 1700 mm for Eucalyptus camaldulensis and from 600 to 900 mm for Corymbia opaca. Several predictions about hydraulic and leaf traits arising from the conclusion that these two species made extensive use of groundwater were supported by additional independent studies of these species in central Australia.
Santini, NS, Cleverly, J, Faux, R, McBean, K, Nolan, RH & Eamus, D 2018, 'Root xylem characteristics and hydraulic strategies of species co-occurring in semi-arid Australia', IAWA Journal, vol. 39, no. 1, pp. 43-62.View/Download from: UTS OPUS or Publisher's site
Xylem traits such as xylem vessel size can influence the efficiency and safety of water transport and thus plant growth and survival. Root xylem traits are much less frequently examined than those of branches despite such studies being critical to our understanding of plant hydraulics. In this study, we investigated primary lateral and sinker roots of six co-occurring species of semi-arid Australia. Two species are restricted to a floodplain, two were sampled only from the adjacent sand plain, and two species co-occur in both habitats. We assessed root wood density, xylem traits (i.e., vessel diameter, fibre and vessel wall thickness), outer pit aperture diameter and calculated theoretical hydraulic conductivity and vessel implosion resistance. We hypothesized that (1) roots have larger xylem vessel diameters and lower wood density than branches of the same species and that (2) there is an inverse correlation between theoretical sapwood hydraulic conductivity and vessel implosion resistance for roots. Variation in root wood density was explained by variations in xylem vessel lumen area across the different species (r2 = 0.73, p = 0.03), as hypothesized. We rejected our second hypothesis, finding instead that the relationship between theoretical hydraulic conductivity and vessel implosion resistance was not maintained in roots of all of our studied species, in contrast to our previous study of branches from the same species. Xylem traits were found to depend upon habitat and eco-hydrological niche, with the groupings including (i) arid-adapted shrubs and trees with shallow lateral roots (Acacia aneura and Psydrax latifolia), (ii) trees restricted to the floodplain habitat, both evergreen (Eucalyptus camaldulensis) and deciduous (Erythrina vespertilio) and (iii) evergreen trees co-occurring in both floodplain and adjacent sand plain habitats (Corymbia opaca and Hakea sp.).
van Gorsel, E, Cleverly, J, Beringer, J, Cleugh, H, Eamus, D, Hutley, LB, Isaac, P & Prober, S 2018, 'Preface: Ozflux: a network for the study of ecosystem carbon and water dynamics across Australia and New Zealand', Biogeosciences, vol. 15, no. 1, pp. 349-352.View/Download from: Publisher's site
He, L, Cleverly, J, Wang, B, Jin, N, Mi, C, Liu, DL & Yu, Q 2018, 'Multi-model ensemble projections of future extreme heat stress on rice across southern China', Theoretical and Applied Climatology, vol. 133, no. 3-4, pp. 1107-1118.View/Download from: UTS OPUS or Publisher's site
Extreme heat events have become more frequent and intense with climate warming, and these heatwaves are a threat to rice production in southern China. Projected changes in heat stress in rice provide an assessment of the potential impact on crop production and can direct measures for adaptation to climate change. In this study, we calculated heat stress indices using statistical scaling techniques, which can efficiently downscale output from general circulation models (GCMs). Data across the rice belt in southern China were obtained from 28 GCMs in the Coupled Model Intercomparison Project phase 5 (CMIP5) with two emissions scenarios (RCP4.5 for current emissions and RCP8.5 for increasing emissions). Multi-model ensemble projections over the historical period (1960–2010) reproduced the trend of observations in heat stress indices (root-mean-square error RMSE = 6.5 days) better than multi-model arithmetic mean (RMSE 8.9 days) and any individual GCM (RMSE 11.4 days). The frequency of heat stress events was projected to increase by 2061–2100 in both scenarios (up to 185 and 319% for RCP4.5 and RCP8.5, respectively), especially in the middle and lower reaches of the Yangtze River. This increasing risk of exposure to heat stress above 30 °C during flowering and grain filling is predicted to impact rice production. The results of our study suggest the importance of specific adaption or mitigation strategies, such as selection of heat-tolerant cultivars and adjustment of planting date in a warmer future world.
Dang, S, Liu, X, Li, X, Yao, M & Zhang, D 2018, 'Changes in different classes of precipitation and the impacts on sediment yield in the Hekouzhen-Longmen region of the Yellow River Basin, China', Advances in Meteorology, vol. 2018.
Barraza, V, Restrepo-Coupe, N, Huete, A, Grings, F, Beringer, J, Cleverly, J & Eamus, D 2017, 'Estimation of latent heat flux over savannah vegetation across the North Australian Tropical Transect from multiple sensors and global meteorological data', Agricultural and Forest Meteorology, vol. 232, pp. 689-703.View/Download from: UTS OPUS or Publisher's site
Latent heat flux (LE) and corresponding water loss in non-moisture-limited ecosystems are well corre-lated to radiation and temperature. By contrast, in savannahs and arid and semi-arid lands LE is mostlydriven by available water and the vegetation exerts a strong control over the rate of transpiration.Therefore, LE models that use optical vegetation indices (VIs) to represent the vegetation component(transpiration as a function of surface conductance, Gs) generally overestimate water fluxes in water-limited ecosystems. In this study, we evaluated and compared optical and passive microwave indexbased retrievals of Gsand LE derived using the Penman-Monteith (PM) formulation over the North Aus-tralian Tropical Transect (NATT). The methodology was evaluated at six eddy covariance (EC) sites fromthe OzFlux network. To parameterize the PM equation for retrievals of LE (PM-Gs), a subset of Gsvalueswas derived from meteorological and EC flux observations and regressed against individual and com-bined satellite indices, from (1) MODIS AQUA: the Normalized Difference Water Index (NDWI) and theEnhanced Vegetation Index (EVI); and from (2) AMSR-E passive microwave: frequency index (FI), polar-ization index (PI), vegetation optical depth (VOD) and soil moisture (SM) products. Similarly, we combinedoptical and passive microwave indices (multi-sensor model) to estimate weekly Gsvalues, and evaluatedtheir spatial and temporal synergies. The multi-sensor approach explained 40–80% of LE variance at somesites, with root mean square errors (RMSE) lower than 20 W/m2and demonstrated better performanceto other satellite-based estimates of LE. The optical indices represented potential Gsassociated with thephenological status of the vegetation (e.g. leaf area index, chlorophyll content) at finer spatial resolution.The microwave indices provided information about water availability and moisture stress (e.g. watercontent in leaves and shallow soil depths, atmospheric demand) at a high tem...
Jones, LA, Kimball, JS, Reichle, RH, Madani, N, Glassy, J, Ardizzone, J, Colliander, A, Cleverly, J, Desai, AR, Eamus, D, Euskirchen, E, Hutley, L, Macfarlane, C & Scott, R 2017, 'The SMAP level 4 carbon product for monitoring ecosystem land-atmosphere CO2 exchange', IEEE Transactions on Geoscience and Remote Sensing, vol. 55, no. 11, pp. 6517-6532.View/Download from: UTS OPUS or Publisher's site
The National Aeronautics and Space Administration's Soil Moisture Active Passive (SMAP) mission Level 4 Carbon (L4C) product provides model estimates of the Net Ecosystem CO2 exchange (NEE) incorporating SMAP soil moisture information. The L4C product includes NEE, computed as total ecosystem respiration less gross photosynthesis, at a daily time step posted to a 9-km global grid by plant functional type. Component carbon fluxes, surface soil organic carbon stocks, underlying environmental constraints, and detailed uncertainty metrics are also included. The L4C model is driven by the SMAP Level 4 Soil Moisture data assimilation product, with additional inputs from the Goddard Earth Observing System, Version 5 weather analysis, and Moderate Resolution Imaging Spectroradiometer satellite vegetation data. The L4C data record extends from March 31, 2015 to present with ongoing production and 8-12 day latency. Comparisons against concurrent global CO2 eddy flux tower measurements, satellite solar-induced canopy florescence, and other independent observation benchmarks show favorable L4C performance and accuracy, capturing the dynamic biosphere response to recent weather anomalies. Model experiments and L4C spatiotemporal variability were analyzed to understand the independent value of soil moisture and SMAP observations relative to other sources of input information. This analysis highlights the potential for microwave observations to inform models where soil moisture strongly controls land CO2 flux variability; however, skill improvement relative to flux towers is not yet discernable within the relatively short validation period. These results indicate that SMAP provides a unique and promising capability for monitoring the linked global terrestrial water and carbon cycles.
Li, L, Wang, Y-P, Beringer, J, Shi, H, Cleverly, J, Cheng, L, Eamus, D, Huete, A, Hutley, L, Lu, X, Piao, S, Zhang, L, Zhang, Y & Yu, Q 2017, 'Responses of LAI to rainfall explain contrasting sensitivities to carbon uptake between forest and non-forest ecosystems in Australia', Science China Life Sciences, vol. 7, no. 1.View/Download from: UTS OPUS or Publisher's site
Non-forest ecosystems (predominant in semi-arid and arid regions) contribute significantly to the increasing trend and interannual variation of land carbon uptake over the last three decades, yet the mechanisms are poorly understood. By analysing the flux measurements from 23 ecosystems in Australia, we found the the correlation between gross primary production (GPP) and ecosystem respiration (Re) was significant for non-forest ecosystems, but was not for forests. In non-forest ecosystems, both GPP and Re increased with rainfall, and, consequently net ecosystem production (NEP) increased with rainfall. In forest ecosystems, GPP and Re were insensitive to rainfall. Furthermore sensitivity of GPP to rainfall was dominated by the rainfall-driven variation of LAI rather GPP per unit LAI in non-forest ecosystems, which was not correctly reproduced by current land models, indicating that the mechanisms underlying the response of LAI to rainfall should be targeted for future model development.
Nolan, RH, Fairweather, KA, Tarin, T, Santini, NS, Cleverly, J, Faux, R & Eamus, D 2017, 'Divergence in plant water-use strategies in semiarid woody species', Functional Plant Biology, vol. 44, no. 11, pp. 1134-1146.View/Download from: UTS OPUS or Publisher's site
Partitioning of water resources amongst plant species within a single climate envelope is possible if the species differ in key hydraulic traits. We examined 11 bivariate trait relationships across nine woody species found in the Ti-Tree basin of central Australia. We found that species with limited access to soil moisture, evidenced by low pre-dawn leaf water potential, displayed anisohydric behaviour (e.g. large seasonal fluctuations in minimum leaf water potential), had greater sapwood density and lower osmotic potential at full turgor. Osmotic potential at full turgor was positively correlated with the leaf water potential at turgor loss, which was, in turn, positively correlated with the water potential at incipient stomatal closure. We also observed divergent behaviour in two species of Mulga, a complex of closely related Acacia species which range from tall shrubs to low trees and dominate large areas of arid and semiarid Australia. These Mulga species had much lower minimum leaf water potentials and lower specific leaf area compared with the other seven species. Finally, one species, Hakea macrocarpa A.Cunn ex.R.Br., had traits that may allow it to tolerate seasonal dryness (through possession of small specific leaf area and cavitation resistant xylem) despite exhibiting cellular water relations that were similar to groundwater-dependent species. We conclude that traits related to water transport and leaf water status differ across species that experience differences in soil water availability and that this enables a diversity of species to exist in this low rainfall environment.
Nolan, RH, Tarin, T, Fairweather, KA, Cleverly, J & Eamus, D 2017, 'Variation in photosynthetic traits related to access to water in semiarid Australian woody species', Functional Plant Biology, vol. 44, no. 11, pp. 1087-1097.View/Download from: UTS OPUS or Publisher's site
Low soil water content can limit photosynthesis by reducing stomatal conductance. Here, we explore relationships among traits pertaining to carbon uptake and pre-dawn leaf water potential (as an index of soil water availability) across eight species found in semiarid central Australia. We found that as pre-dawn leaf water potential declined, stomatal limitations to photosynthesis increased, as did foliar nitrogen, which enhanced photosynthesis. Nitrogen-fixing Acacia species had higher foliar nitrogen concentrations compared with non-nitrogen fixing species, although there was considerable variability of traits within the Acacia genus. From principal component analysis we found that the most dissimilar species was Acacia aptaneura Maslin & J.E.Reid compared with both Eucalyptus camaldulensis Dehnh. and Corymbia opaca. (D.J.Carr & S.G.M.Carr) K.D.Hill & L.A.S.Johnson, having both the largest foliar N content, equal largest leaf mass per area and experiencing the lowest pre-dawn water potential of all species. A. aptaneura has shallow roots and grows above a hardpan that excludes access to groundwater, in contrast to E. camaldulensis and C. opaca, which are known to access groundwater. We conclude that ecohydrological niche separation is an important factor driving the variability of within-biome traits related to carbon gain. These observations have important implications for global vegetation models, which are parameterised with many of the traits measured here, but are often limited by data availability.
Shi, H, Li, L, Eamus, D, Huete, A, Cleverly, J, Tian, X, Yu, Q, Wang, S, Montagnani, L, Magliulo, V, Rotenberg, E, Pavelka, M & Carrara, A 2017, 'Assessing the ability of MODIS EVI to estimate terrestrial ecosystem gross primary production of multiple land cover types', Ecological Indicators, vol. 72, pp. 153-164.View/Download from: UTS OPUS or Publisher's site
tTerrestrial ecosystem gross primary production (GPP) is the largest component in the global carbon cycle.The enhanced vegetation index (EVI) has been proven to be strongly correlated with annual GPP withinseveral biomes. However, the annual GPP-EVI relationship and associated environmental regulationshave not yet been comprehensively investigated across biomes at the global scale. Here we exploredrelationships between annual integrated EVI (iEVI) and annual GPP observed at 155 flux sites, whereGPP was predicted with a log-log model: ln(GPP) = a × ln(iEVI) + b. iEVI was computed from MODISmonthly EVI products following removal of values affected by snow or cold temperature and withoutcalculating growing season duration. Through categorisation of flux sites into 12 land cover types, theability of iEVI to estimate GPP was considerably improved (R2from 0.62 to 0.74, RMSE from 454.7 to368.2 g C m−2yr−1). The biome-specific GPP-iEVI formulae generally showed a consistent performancein comparison to a global benchmarking dataset (R2= 0.79, RMSE = 387.8 g C m−2yr−1). Specifically, iEVIperformed better in cropland regions with high productivity but poorer in forests. The ability of iEVI inestimating GPP was better in deciduous biomes (except deciduous broadleaf forest) than in evergreendue to the large seasonal signal in iEVI in deciduous biomes. Likewise, GPP estimated from iEVI was ina closer agreement to global benchmarks at mid and high-latitudes, where deciduous biomes are morecommon and cloud cover has a smaller effect on remote sensing retrievals. Across biomes, a significant andnegative correlation (R2= 0.37, p < 0.05) was observed between the strength (R2) of GPP-iEVI relationshipsand mean annual maximum leaf area index (LAImax), and the relationship between the strength andmean annual precipitation followed a similar trend. LAImaxalso revealed a scaling effect on GPP-iEVIrelationships. Our results suggest that iEVI provides a very simple but robust approach to ...
Zolfaghar, S, Villalobos-Vega, R, Zeppel, M, Cleverly, J, Rumman, R, Hingee, M, Boulain, N, Li, Z, Eamus, D & Tognetti, R 2017, 'Transpiration of Eucalyptus woodlands across a natural gradient of depth-to-groundwater', Tree Physiology, vol. 37, no. 7, pp. 961-975.View/Download from: UTS OPUS or Publisher's site
Adnan, RM, Yuan, X, Kisi, O & Anam, R 2017, 'Improving Accuracy of River Flow Forecasting Using LSSVR with Gravitational Search Algorithm', Advances in Meteorology, vol. 2017, pp. 1-23.View/Download from: Publisher's site
River flow prediction is essential in many applications of water resources planning and management. In this paper, the accuracy of multivariate adaptive regression splines (MARS), model 5 regression tree (M5RT), and conventional multiple linear regression (CMLR) is compared with a hybrid least square support vector regression-gravitational search algorithm (HLGSA) in predicting monthly river flows. In the first part of the study, all three regression methods were compared with each other in predicting river flows of each basin. It was found that the HLGSA method performed better than the MARS, M5RT, and CMLR in river flow prediction. The effect of log transformation on prediction accuracy of the regression methods was also examined in the second part of the study. Log transformation of the river flow data significantly increased the prediction accuracy of all regression methods. It was also found that log HLGSA (LHLSGA) performed better than the other regression methods. In the third part of the study, the accuracy of the LHLGSA and HLGSA methods was examined in river flow estimation using nearby river flow data. On the basis of results of all applications, it was found that LHLGSA and HLGSA could be successfully used in prediction and estimation of river flow.
Chen, X, Su, Z, Ma, J, Cleverly, J & Liddell, M 2017, 'An accurate estimate of monthly mean land surface temperatures from MODIS clearsky retrievals', Journal of Hydrometeorology, vol. 18, no. 10, pp. 2827-2847.View/Download from: UTS OPUS or Publisher's site
AbstractMODIS thermal sensors can provide us with global land surface temperature (LST) several times each day, but have difficulty in obtaining information from the land surface in cloudy situations. As a result the monthly day or night LST products [Terra monthly day LST (TMD), Terra monthly night LST (TMN), Aqua monthly day LST (AMD), Aqua monthly night LST (AMN)] are the average LST values calculated over a variable number of clear-sky days in a month. Is it possible to derive an accurate estimate of monthly mean LST based on averaging of the multi-daily overpasses of MODIS sensors? In-situ ground measurements and ERA-Interim re-analyses data, both of which provide continuous information in either clear or cloudy conditions, have been used to validate our approach. Using LST measurements from 156 ground flux towers, it was found that the three mean values , , (mean bias 0.19, 0.59, 0.40 K respectively) can all provide a reliable estimate of all-sky monthly mean LST. Of the three means we recommend the use of for monthly mean LST in climate studies as it provides the most complete coverage. When retrievals from either Terra or Aqua are not available, then either or may be used to fill the gaps. The intrinsic error in the MODIS monthly mean LST cannot be explained from monthly mean view time, view angle and clear sky ratio. MODIS monthly LST calculated using this approach (RMSE=2.65, mean bias< ±1 K) will have wide applicability for climate studies and numerical model evaluation.
Isaac, P, Cleverly, J, McHugh, I, van Gorsel, E, Ewenz, C & Beringer, J 2017, 'OzFlux data: network integration from collection to curation', Biogeosciences, vol. 14, no. 12, pp. 2903-2928.View/Download from: UTS OPUS or Publisher's site
Measurement of the exchange of energy and mass between the surface and the atmospheric boundary-layer by the eddy covariance technique has undergone great change in the last 2 decades. Early studies of these exchanges were confined to brief field campaigns in carefully controlled conditions followed by months of data analysis. Current practice is to run tower-based eddy covariance systems continuously over several years due to the need for continuous monitoring as part of a global effort to develop local-, regional-, continental- and global-scale budgets of carbon, water and energy. Efficient methods of processing the increased quantities of data are needed to maximise the time available for analysis and interpretation. Standardised methods are needed to remove differences in data processing as possible contributors to observed spatial variability. Furthermore, public availability of these data sets assists with undertaking global research efforts. The OzFlux data path has been developed (i) to provide a standard set of quality control and post-processing tools across the network, thereby facilitating inter-site integration and spatial comparisons; (ii) to increase the time available to researchers for analysis and interpretation by reducing the time spent collecting and processing data; (iii) to propagate both data and metadata to the final product; and (iv) to facilitate the use of the OzFlux data by adopting a standard file format and making the data available from web-based portals. Discovery of the OzFlux data set is facilitated through incorporation in FLUXNET data syntheses and the publication of collection metadata via the RIF-CS format. This paper serves two purposes. The first is to describe the data sets, along with their quality control and post-processing, for the other papers of this Special Issue. The second is to provide an example of one solution to the data collection and curation challenges that are encountered by similar flux tower networks wo...
Lin, H, Chen, Y, Song, Q, Fu, P, Cleverly, J, Magliulo, V, Law, B, Gough, CM, Hörtnagl, L, Di Gennaro, F, Matteucci, G, Montagnani, L, Duce, P, Shao, C, Kato, T, Bonal, D, Paul-Limoges, E, Beringer, J, Grace, J & Fan, Z 2017, 'Quantifying deforestation and forest degradation with thermal response', Science of the Total Environment, vol. 607–608, pp. 1286-1292.View/Download from: UTS OPUS or Publisher's site
Deforestation and forest degradation cause the deterioration of resources and ecosystem services. However, there are still no operational indicators to measure forest status, especially for forest degradation. In the present study, we analysed the thermal response number (TRN, calculated by daily total net radiation divided by daily temperature range) of 163 sites including mature forest, disturbed forest, planted forest, shrubland, grassland, savanna vegetation and cropland. TRN generally increased with latitude, however the regression of TRN against latitude differed among vegetation types. Mature forests are superior as thermal buffers, and had significantly higher TRN than disturbed and planted forests. There was a clear boundary between TRN of forest and non-forest vegetation (i.e. grassland and savanna) with the exception of shrubland, whose TRN overlapped with that of forest vegetation. We propose to use the TRN of local mature forest as the optimal TRN (TRNopt). A forest with lower than 75% of TRNopt was identified as subjected to significant disturbance, and forests with 66% of TRNopt was the threshold for deforestation within the absolute latitude from 30° to 55°. Our results emphasized the irreplaceable thermal buffer capacity of mature forest. TRN can be used for early warning of deforestation and degradation risk. It is therefore a valuable tool in the effort to protect forests and prevent deforestation.
Ma, X, Feng, Q, Su, Y, Yu, T & Jin, H 2017, 'Forest Evapotranspiration and Energy Flux Partitioning Based on Eddy Covariance Methods in an Arid Desert Region of Northwest China', Advances in Meteorology, vol. 2017, pp. 1-10.View/Download from: Publisher's site
In this study, the characteristics of energy flux partitioning and evapotranspiration of P. euphratica forests were examined in the extreme arid region of Northwest China. Energy balance closure of the ecosystem was approximately 72% (H + LE = 0.72 ∗ (Rn-G)+7.72, r2=0.79, n=12095), where Rn is the net radiation, G is the soil heat flux, H is the sensible heat flux, and LE is the latent heat flux. LE was the main term of energy consumption at annual time scale because of higher value in the growing season. The ratios of the latent (LE) and sensible (H) heat fluxes to net radiation ...
Thibault, JR, Cleverly, JR & Dahm, CN 2017, 'Long-term Water Table Monitoring of Rio Grande Riparian Ecosystems for Restoration Potential Amid Hydroclimatic Challenges.', Environmental Management, vol. 60, no. 6, pp. 1101-1115.View/Download from: UTS OPUS or Publisher's site
Hydrological processes drive the ecological functioning and sustainability of cottonwood-dominated riparian ecosystems in the arid southwestern USA. Snowmelt runoff elevates groundwater levels and inundates floodplains, which promotes cottonwood germination. Once established, these phreatophytes rely on accessible water tables (WTs). In New Mexico's Middle Rio Grande corridor diminished flooding and deepening WTs threaten native riparian communities. We monitored surface flows and riparian WTs for up to 14 years, which revealed that WTs and surface flows, including peak snowmelt discharge, respond to basin climate conditions and resource management. WT hydrographs influence the composition of riparian communities and can be used to assess if potential restoration sites meet native vegetation tolerances for WT depths, rates of recession, and variability throughout their life stages. WTs were highly variable in some sites, which can preclude native vegetation less adapted to deep drawdowns during extended droughts. Rates of WT recession varied between sites and should be assessed in regard to recruitment potential. Locations with relatively shallow WTs and limited variability are likely to be more viable for successful restoration. Suitable sites have diminished greatly as the once meandering Rio Grande has been constrained and depleted. Increasing demands on water and the presence of invasive vegetation better adapted to the altered hydrologic regime further impact native riparian communities. Long-term monitoring over a range of sites and hydroclimatic extremes reveals attributes that can be evaluated for restoration potential.
Beringer, J, Hutley, LB, McHugh, I, Arndt, SK, Campbell, D, Cleugh, HA, Cleverly, J, Resco de Dios, V, Eamus, D, Evans, B, Ewenz, C, Grace, P, Griebel, A, Haverd, V, Hinko-Najera, N, Huete, A, Isaac, P, Kanniah, K, Leuning, R, Liddell, MJ, Macfarlane, C, Meyer, W, Moore, C, Pendall, E, Phillips, A, Phillips, RL, Prober, SM, Restrepo-Coupe, N, Rutledge, S, Schroder, I, Silberstein, R, Southall, R, Yee, MS, van Gorsel, E, Vote, C, Walker, J & Wardlaw, T 2016, 'An introduction to the Australian and New Zealand flux tower network – OzFlux', Biogeosciences, vol. 13, pp. 5895-5916.View/Download from: UTS OPUS or Publisher's site
OzFlux is the regional Australian and New
Zealand flux tower network that aims to provide a
continental-scale national research facility to monitor and assess
trends, and improve predictions, of Australia's terrestrial
biosphere and climate. This paper describes the evolution,
design, and current status of OzFlux as well as provides an
overview of data processing.We analyse measurements from
all sites within the Australian portion of the OzFlux network
and two sites from New Zealand. The response of the Australian
biomes to climate was largely consistent with global
studies except that Australian systems had a lower ecosystem
water-use efficiency. Australian semi-arid/arid ecosystems
are important because of their huge extent (70 %) and they
have evolved with common moisture limitations. We also
found that Australian ecosystems had a similar radiationuse
efficiency per unit leaf area compared to global values
that indicates a convergence toward a similar biochemical
efficiency. The two New Zealand sites represented extremes
in productivity for a moist temperate climate zone, with the
grazed dairy farm site having the highest GPP of any OzFlux
site (2620 gCm 2 yr 1/ and the natural raised peat bog site
having a very low GPP (820 gCm 2 yr 1/. The paper discusses
the utility of the flux data and the synergies between
flux, remote sensing, and modelling. Lastly, the paper looks
ahead at the future direction of the network and concludes
that there has been a substantial contribution by OzFlux, and
considerable opportunities remain to further advance our understanding
of ecosystem response to disturbances, including
drought, fire, land-use and land-cover change, land management,
and climate change, which are relevant both nationally
and internationally. It is suggested that a synergistic approach
is required to address all of the spatial, ecological, human,
and cultural challenges of managing the delicately balanced
ecosystems in Australasia.
Cleverly, J, Eamus, D, Luo, Q, Coupe, NR, 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.View/Download from: UTS OPUS or Publisher's site
Cleverly, J, Eamus, D, Restrepo Coupe, N, Chen, C, Maes, W, Li, L, Faux, R, Santini, NS, 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.View/Download from: UTS OPUS or Publisher's site
© 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 (θ) 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 θ above the hardpan was rapid and depended upon precipitation amount: 150mm storm-1 resulted in saturation of θ 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 θ 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.
Cleverly, J, Eamus, D, Van Gorsel, E, Chen, C, Rumman, R, Luo, Q, Coupe, NR, 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.View/Download from: UTS OPUS or Publisher's site
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.View/Download from: UTS OPUS or Publisher's site
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 1981−2012. 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.
Eamus, D, Huete, A, Cleverly, J, Nolan, RH, Ma, X, Tarin, T & Santini, NS 2016, 'Mulga, a major tropical dry open forest of Australia: recent insights to carbon and water fluxes', Environmental Research Letters, vol. 11.View/Download from: UTS OPUS or Publisher's site
Mulga, comprised of a complex of closely related Acacia spp., grades from a low open forest to tall
shrublands in tropical and sub-tropical arid and semi-arid regions of Australia and experiences warmto-
hot annual temperatures and a pronounced dry season. This short synthesis of current knowledge
briefly outlines the causes of the extreme variability in rainfall characteristic of much of central
Australia, and then discusses the patterns and drivers of variability in carbon and water fluxes of a
central Australian low open Mulga forest. Variation in phenology and the impact of differences in the
amount and timing of precipitation on vegetation function are then discussed.Weuse field
observations, with particular emphasis on eddy covariance data, coupled with modelling and remote
sensing products to interpret inter-seasonal and inter-annual patterns in the behaviour of this
ecosystem.Weshow that Mulga can vary between periods of near carbon neutrality to periods of being
a significant sink or source for carbon, depending on both the amount and timing of rainfall. Further,
we demonstrate that Mulga contributed significantly to the 2011 global land sink anomaly, a result
ascribed to the exceptional rainfall of 2010/2011. Finally, we compare and contrast the hydraulic traits
of three tree species growing close to the Mulga and show how each species uses different
combinations of trait strategies (for example, sapwood density, xylem vessel implosion resistance,
phenological guild, access to groundwater and Huber value) to co-exist in this semi-arid environment.
Understanding the inter-annual variability in functional behaviour of this important arid-zone biome
and mechanisms underlying species co-existence will increase our ability to predict trajectories of
carbon and water balances for future changing climates.
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, vol. 568, pp. 1263-1274.View/Download from: UTS OPUS or Publisher's site
Ecosystem monitoring networks aim to collect data on physical, chemical and biological systems and their interactions that shape the biosphere. Here we introduce the Australian SuperSite Network that, along with complementary facilities of Australia's Terrestrial Ecosystem Research Network (TERN), delivers field infrastructure and diverse, ecosystem-related datasets for use by researchers, educators and policy makers. The SuperSite Network uses infrastructure replicated across research sites in different biomes, to allow comparisons across ecosystems and improve scalability of findings to regional, continental and global scales. This conforms with the approaches of other ecosystem monitoring networks such as Critical Zone Observatories, the U.S. National Ecological Observatory Network; Analysis and Experimentation on Ecosystems, Europe; Chinese Ecosystem Research Network; International Long Term Ecological Research network and the United States Long Term Ecological Research Network. The Australian SuperSite Network currently involves 10 SuperSites across a diverse range of biomes, including tropical rainforest, grassland and savanna; wet and dry sclerophyll forest and woodland; and semi-arid grassland, woodland and savanna. The focus of the SuperSite Network is on using vegetation, faunal and biophysical monitoring to develop a process-based understanding of ecosystem function and change in Australian biomes; and to link this with data streams provided by the series of flux towers across the network. The Australian SuperSite Network is also intended to support a range of auxiliary researchers who contribute to the growing body of knowledge within and across the SuperSite Network, public outreach and education to promote environmental awareness and the role of ecosystem monitoring in the management of Australian environments.
Ma, X, Huete, A, Cleverly, J, Eamus, D, Chevallier, F, Joiner, J, Poulter, B, Zhang, Y, Guanter, L, Meyer, W, Xie, Z & Ponce-Campos, G 2016, 'Drought rapidly diminishes the large net CO2 uptake in 2011 over semi-arid Australia', Scientific Reports, vol. 6.View/Download from: UTS OPUS or Publisher's site
Each year, terrestrial ecosystems absorb more than a quarter of the anthropogenic carbon emissions, termed as land carbon sink. An exceptionally large land carbon sink anomaly was recorded in 2011, of which more than half was attributed to Australia. However, the persistence and spatially attribution of this carbon sink remain largely unknown. Here we conducted an observation-based study to characterize the Australian land carbon sink through the novel coupling of satellite retrievals of atmospheric CO2 and photosynthesis and in-situ flux tower measures. We show the 2010–11 carbon sink was primarily ascribed to savannas and grasslands. When all biomes were normalized by rainfall, shrublands however, were most efficient in absorbing carbon. We found the 2010–11 net CO2 uptake was highly transient with rapid dissipation through drought. The size of the 2010–11 carbon sink over Australia (0.97 Pg) was reduced to 0.48 Pg in 2011–12, and was nearly eliminated in 2012–13 (0.08 Pg). We further report evidence of an earlier 2000–01 large net CO2 uptake, demonstrating a repetitive nature of this land carbon sink. Given a significant increasing trend in extreme wet year precipitation over Australia, we suggest that carbon sink episodes will exert greater future impacts on global carbon cycle.
Restrepo Coupe, N, Huete, A, Davies, K, Cleverly, J, Beringer, J, Eamus, D, van Gorsel, E, Hutley, LB & Meyer, WS 2016, 'MODIS vegetation products as proxies of photosynthetic potential along a gradient of meteorologically and biologically driven ecosystem productivity', Biogeosciences, vol. 13, no. 19, pp. 5587-5608.View/Download from: UTS OPUS or Publisher's site
A direct relationship between gross ecosystem productivity (GEP) estimated by the eddy covariance (EC) method and Moderate Resolution Imaging Spectroradiometer (MODIS) vegetation indices (VIs) has been observed in many temperate and tropical ecosystems. However, in Australian evergreen forests, and particularly sclerophyll and temperate woodlands, MODIS VIs do not capture seasonality of GEP. In this study, we re-evaluate the connection between satellite and flux tower data at four contrasting Australian ecosystems, through comparisons of GEP and four measures of photosynthetic potential, derived via parameterization of the light response curve: ecosystem light use efficiency (LUE), photosynthetic capacity (Pc), GEP at saturation (GEPsat), and quantum yield (α), with MODIS vegetation satellite products, including VIs, gross primary productivity (GPPMOD), leaf area index (LAIMOD), and fraction of photosynthetic active radiation (fPARMOD). We found that satellite-derived biophysical products constitute a measurement of ecosystem structure (e.g. leaf area index – quantity of leaves) and function (e.g. leaf level photosynthetic assimilation capacity – quality of leaves), rather than GEP. Our results show that in primarily meteorological-driven (e.g. photosynthetic active radiation, air temperature, and/or precipitation) and relatively aseasonal ecosystems (e.g. evergreen wet sclerophyll forests), there were no statistically significant relationships between GEP and satellite-derived measures of greenness. In contrast, for phenology-driven ecosystems (e.g. tropical savannas), changes in the vegetation status drove GEP, and tower-based measurements of photosynthetic activity were best represented by VIs. We observed the highest correlations between MODIS products and GEP in locations where key meteorological variables and vegetation phenology were synchronous (e.g. semi-arid Acacia woodlands) and low correlation at locations where they were asynchronous (e.g. Mediterran...
Santini, NS, 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.View/Download from: UTS OPUS or Publisher's site
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 (δ13C) 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 δ13C 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 cm−3 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.
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.View/Download from: UTS OPUS or Publisher's site
Zhuang, W, Cheng, L, Whitley, R, Shi, H, Beringer, J, Wang, Y, He, L, Cleverly, J, 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.View/Download from: UTS OPUS
Cleverly, J 2016, 'Postcards from the Field', EOS Transactions of the American Geophysical Union, vol. 97, pp. C3-C3.
Griebel, A, Bennett, LT, Metzen, D, Cleverly, J, Burba, G & Arndt, SK 2016, 'Effects of inhomogeneities within the flux footprint on the interpretation of seasonal, annual, and interannual ecosystem carbon exchange', Agricultural and Forest Meteorology, vol. 221, pp. 50-60.View/Download from: Publisher's site
Guo, J, Zhang, H, Cui, T, He, Y, Zhang, J, Guo, K, Hou, C & Liu, R 2016, 'Remote Sensing Observations of the Winter Yellow Sea Warm Current Invasion into the Bohai Sea, China', Advances in Meteorology, vol. 2016, pp. 1-10.View/Download from: Publisher's site
Using ASCAT, QuikSCAT, and MODIS data, we analyzed the sea surface wind field, temperature, salinity, and chlorophyll concentrations in the mixed zone between the Bohai Sea and Yellow Sea in the winter (the period of winter 2013 included December 2013 and January-February 2014) from 2002 to 2013. We found that the intrusion of the Yellow Sea Warm Current into the Bohai Sea occurred three times in the winters of 2007 (strongest), 2004, and 2013 (weakest) during this 12-year period. We present detailed validation of the intrusion in 2013. This study shows that the intrusion of the Yellow Sea Warm Current into the Bohai Sea occurred when the wind speed, sea surface temperature, and salinity were above (or close to) the multiyear average and the chlorophyll concentration was less than the multiyear average.
Haverd, V, Smith, B, Raupach, M, Briggs, P, Nieradzik, L, Beringer, J, Hutley, L, Trudinger, CM & Cleverly, J 2016, 'Coupling carbon allocation with leaf and root phenology predicts tree–grass partitioning along a savanna rainfall gradient', Biogeosciences, vol. 13, pp. 761-779.View/Download from: UTS OPUS or Publisher's site
Holgate, CM, De Jeu, RAM, van Dijk, AIJM, Liu, YY, Renzullo, LJ, Vinodkumar, Dharssi, I, Parinussa, RM, Van Der Schalie, R, Gevaert, A, Walker, J, McJannet, D, Cleverly, J, Haverd, V, Trudinger, CM & Briggs, PR 2016, 'Comparison of remotely sensed and modelled soil moisture data sets across Australia', Remote Sensing of Environment, vol. 186, pp. 479-500.View/Download from: Publisher's site
Liu, S, Yan, D, Wang, H, Li, C, Weng, B & Qin, T 2016, 'Standardized Water Budget Index and Validation in Drought Estimation of Haihe River Basin, North China', Advances in Meteorology, vol. 2016, pp. 1-10.View/Download from: Publisher's site
The physical-based drought indices such as the self-calibrated Palmer Drought Severity Index (sc-PDSI) with the fixed time scale is inadequate for the multiscalar drought assessment, and the multiscalar drought indices including Standardized Precipitation Index (SPI), Reconnaissance Drought Index (RDI), and Standardized Precipitation Evapotranspiration Index (SPEI) based on the meteorological factors are lack of physical mechanism and cannot depict the actual water budget. To fill this gap, the Standardized Water Budget Index (SWBI) is constructed based on the difference between areal precipitation and actual evapotranspiration (AET), which can describe the actual water budget but also assess the drought at multiple time scales. Then, sc-PDSI was taken as the reference drought index to compare with multiscalar drought indices at different time scale in Haihe River basin. The result shows that SWBI correlates better with sc-PDSI and the RMSE of SWBI is less than other multiscalar drought indices. In addition, all of drought indices show a decreasing trend in Haihe River Basin, possibly due to the decreasing precipitation from 1961 to 2010. The decreasing trends of SWBI were significant and consistent at all the time scales, while the decreasing trends of other multiscalar drought indices are insignificant at time scale less than 3 months.
Pannekoucke, O, Cébron, P, Oger, N & Arbogast, P 2016, 'From the Kalman Filter to the Particle Filter: A Geometrical Perspective of the Curse of Dimensionality', Advances in Meteorology, vol. 2016, pp. 1-18.View/Download from: Publisher's site
The aim of this contribution is to provide a description of the difference between Kalman filter and particle filter when the state space is of high dimension. In the Gaussian framework, KF and PF give the same theoretical result. However, in high dimension and using finite sampling for the Gaussian distribution, the PF is not able to reproduce the solution produced by the KF. This discrepancy is highlighted from the convergence property of the Gaussian law toward a hypersphere: in high dimension, any finite sample of a Gaussian law lies within a hypersphere centered in the mean of the Gaussian law and of radius square-root of the trace of the covariance matrix. This concentration of probability suggests the use of norm as a criterium that discriminates whether a forecast sample can be compatible or not with a given analysis state. The contribution illustrates important characteristics that have to be considered for the high dimension but does not introduce a new approach to face the curse of dimensionality.
van Gorsel, E, Wolf, S, Cleverly, J, Isaac, P, Haverd, V, Ewenz, C, Arndt, S, Beringer, J, Resco de Dios, V, Evans, BJ, Griebel, A, Hutley, LB, Keenan, T, Kljun, N, Macfarlane, C, Meyer, WS, McHugh, I, Pendall, E, Prober, SM & Silberstein, R 2016, 'Carbon uptake and water use in woodlands and forests in southernAustralia during an extreme heat wave event in the 'AngrySummer' of 2012/2013', Biogeosciences, vol. 13, pp. 5947-5964.View/Download from: UTS OPUS or Publisher's site
Zhou, F-C, Song, X, Leng, P, Wu, H & Tang, B-H 2016, 'An Algorithm for Retrieving Precipitable Water Vapor over Land Based on Passive Microwave Satellite Data', Advances in Meteorology, vol. 2016, pp. 1-11.View/Download from: Publisher's site
Precipitable water vapor (PWV) is one of the most variable components of the atmosphere in both space and time. In this study, a passive microwave-based retrieval algorithm for PWV over land without land surface temperature (LST) data was developed. To build the algorithm, two assumptions exist: (1) land surface emissivities (LSE) at two adjacent frequencies are equal and (2) there are simple parameterizations that relate transmittance, atmospheric effective radiating temperature, and PWV. Error analyses were performed using radiosonde sounding observations from Zhangye, China, and CE318 measurements of Dalanzadgad (43°34′37′′N, 104°25′8′′E) and Singapore (1°17′52′′N, 103°46′48′′E) sites from Aerosol Robotic Network (AERONET), respectively. In Zhangye, the algorithm had a Root Mean Square Error (RMSE) of 4.39 mm and a bias of 0.36 mm on cloud-free days, while on cloudy days there was an RMSE of 4.84 mm and a bias of 0.52 mm because of the effect of liquid water in clouds. The validations in Dalanzadgad and Singapore sites showed that the retrieval algorithm had an RMSE of 4.73 mm and a bias of 0.84 mm and the bigger errors appeared when the water vapor was very dry or very moist.
Cleverly, J, Thibault, JR, Teet, SB, Tashjian, P, Hipps, LE, Dahm, CN & 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.View/Download from: UTS OPUS or Publisher's site
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 (700–800Wm−2), latent heat flux was the largest energy flux, with annual values
of evapotranspiration exceeding annual precipitation by 250–600%. Evaporative cooling dominated the energy fluxes of both forest
types, although cottonwood generatedmuch lower daily values of sensible heat flux (<−5MJm−2 d−1). 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.View/Download from: UTS OPUS or Publisher's site
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
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...
Shanafield, M, Cook, PG, Gutierrez-Jurado, HA, 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.View/Download from: UTS OPUS or Publisher's site
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.View/Download from: UTS OPUS or Publisher's site
Kutty, G & Wang, X 2015, 'A Comparison of the Impacts of Radiosonde and AMSU Radiance Observations in GSI Based 3DEnsVar and 3DVar Data Assimilation Systems for NCEP GFS', Advances in Meteorology, vol. 2015, pp. 1-17.View/Download from: Publisher's site
The impact of observations can be dependent on many factors in a data assimilation (DA) system including data quality control, preprocessing, skill of the model, and the DA algorithm. The present study focuses on comparing the impacts of observations assimilated by two different DA algorithms. A three-dimensional ensemble-variational (3DEnsVar) hybrid data assimilation system was recently developed based on the Gridpoint Statistical Interpolation (GSI) data assimilation system and was implemented operationally for the National Center for Environmental Prediction (NCEP) Global Forecast System (GFS). One question to address is, how the impacts of observations on GFS forecasts differ when assimilated by the traditional GSI-three dimensional variational (3DVar) and the new 3DEnsVar. Experiments were conducted over a 6-week period during Northern Hemisphere winter season at a reduced resolution. For both the control and data denial experiments, the forecasts produced by 3DEnsVar were more accurate than GSI3DVar experiments. The results suggested that the observations were better and more effectively exploited to increment the background forecast in 3DEnsVar. On the other hand, in GSI3DVar, where the observation will be making mostly local, isotropic increments without proper flow dependent extrapolation is more sensitive to the number and types observations assimilated.
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.View/Download from: UTS OPUS or Publisher's site
Ma, X, Huete, A, Yu, Q, Restrepo-Coupe, N, Beringer, J, Hutley, LB, Kanniah, KD, 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.View/Download from: UTS OPUS or Publisher's site
Shi, H, Li, L, Eamus, D, Cleverly, J, Huete, A, Beringer, J, Yu, Q, van Gorsel, E & Hutley, L 2014, 'Intrinsic climate dependency of ecosystem light and water-use-efficiencies across Australian biomes', Environmental Research Letters, vol. 9, no. 10, pp. 104002-104002.View/Download from: UTS OPUS or Publisher's site
The sensitivity of ecosystem gross primary production (GPP) to availability of water and photosynthetically active radiation (PAR) differs among biomes. Here we investigated variations of ecosystem light-use-efficiency (eLUE: GPP/PAR) and water-use-efficiency (eWUE: GPP/evapotranspiration) among seven Australian eddy covariance sites with differing annual precipitation, species composition and temperature. Changes to both eLUE and eWUE were primarily correlated with atmospheric vapor pressure deficit (VPD) at multiple temporal scales across biomes, with minor additional correlations observed with soil moisture and temperature. The effects of leaf area index on eLUE and eWUE were also relatively weak compared to VPD, indicating an intrinsic dependency of eLUE and eWUE on climate. Additionally, eLUE and eWUE were statistically different for biomes between summer and winter, except eWUE for savannas and the grassland. These findings will improve our understanding of how light- and water-use traits in Australian ecosystems may respond to climate change.
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.View/Download from: UTS OPUS or Publisher's site
He, L, Cleverly, J, Chen, C, Yang, X, Li, J, Liu, W & Yu, Q 2014, 'Diverse responses of winter wheat yield and water use to climate change and variability on the semiarid Loess Plateau in China', Agronomy Journal, vol. 106, pp. 1169-1178.View/Download from: UTS OPUS or Publisher's site
Crop production and water use in rainfed cropland are vulnerable to climate change. This study was to quantify diverse responses of winter wheat (Triticum aestivum L.) yield and water use to climate change on the Loess Plateau (LP) under different combinations of climatic variables. The crop model APSIM was validated against field experimental data and applied to calculate yield and water use at 18 sites on the LP during 1961 to 2010. The coefficient of variation of yield ranged from 12 to 66%, in which the vulnerability of yield increased from the southeast (12%) to the northwest (66%). This change was attributed to the gradual increase in precipitation variation from the southeast to the northwest. An obvious warming trend during 1961 to 2010 resulted in a significant decrease in the growth duration by 1 to 5 d decade1. The yield at 12 sites was significantly reduced by 120 to 720 kg ha1 decade1. Evapotranspiration was significantly decreased by 1 to 26 mm decade1; however, water use efficiency at most sites showed no significant trend. Eighteen sites were classified into three climatic zones by cluster analysis: high temperaturehigh precipitationlow radiation (HHL), medium temperaturemedium precipitationmedium radiation (MMM), and low temperaturelow precipitationhigh radiation (LLH). The trend of decreasing yield was smallest in the HHL cluster because of a minimal reduction in precipitation, while decreasing trends in yield and evapotranspiration were larger in the LLH and MMM because of larger reductions in precipitation. The results imply that among strategies such as breeding for long duration or drought tolerance, modification of the planting date will be necessary to avoid high temperatures associated with climate change.
Donohue, RJ, Hume, IH, Roderick, ML, McVicar, TR, Beringer, J, Hutley, L, Gallant, JC, Austin, JM, van Gorsel, E, Cleverly, JR, Meyer, WS & Arndt, SK 2014, 'Evaluation of the remote-sensing-based DIFFUSE model for estimating photosynthesis of vegetation', REMOTE SENSING OF ENVIRONMENT, vol. 155, pp. 349-365.View/Download from: Publisher's site
Cleverly, J, Boulain, NP, Villalobos-Vega, R, Grant, NM, 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.View/Download from: UTS OPUS or Publisher's site
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 ± 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, Chen, C, Boulain, NP, Villalobos-Vega, R, Faux, R, Grant, NM, 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.View/Download from: UTS OPUS or Publisher's site
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.
Eamus, D, Boulain, NP, Cleverly, J & Breshears, DD 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.View/Download from: UTS OPUS or Publisher's site
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°C or +5°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
Eamus, D, Cleverly, J, Boulain, NP, Grant, NM, 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.View/Download from: UTS OPUS or Publisher's site
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, KP, Broich, M, Ratana, P, Beringer, J, Hutley, LB, Cleverly, J, Boulain, NP & 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.View/Download from: UTS OPUS or Publisher's site
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°S, to around 17.7°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.
Martinet, MC, Vironi, ER, Cleverly, JR, Thibault, JR, Schuetz, JF & Dahm, CN 2009, 'On groundwater fluctuations, evapotranspiration, and understory removal in riparian corridors', Water resources research, vol. 45, pp. 1-19.View/Download from: UTS OPUS or Publisher's site
This study utilizes 7 years of continuously monitored groundwater-level data from four sites along the Río Grande riparian corridor in central New Mexico to calculate evapotranspiration from groundwater and assess impacts of understory vegetation removal during a restoration project. Diurnal groundwater fluctuation measurements were used to compare the well-known White method for estimating evapotranspiration from groundwater (ETg) to colocated measurements of total riparian evapotranspiration (ET) measured using the eddy covariance method. On average, the two methods were linearly correlated and had similar variability, but groundwater hydrograph estimates of ETg tended to be larger than tower ET estimates. Average ETg estimates for two wells at one site ranged from 91.45% to 164.77% of measured tower ET estimates, but were also shown to range from 57.35% to 254.34% at another site. Comparisons between the methods improved with deeper water tables, reduced groundwater and river connectivity, and where soil profiles were dominated by coarse-sized particles. Using a range of texture-based estimates of specific yield (Sy) with water table position improves the field application of the White method. River-induced fluctuations in groundwater increased the variability of ETg measurements. Removal of understory vegetation at one site resulted in a small but significant reduction in diel groundwater fluctuation amplitude of 1921%. Caution is required when understory vegetation removal is used as a means to decrease overall riparian ET. Diel groundwater fluctuation amplitudes can be useful in gauging the hydrological effects of vegetation removal. Riparian groundwater hydrographs are critical to investigating the hydrologic connectivity between river and shallow groundwater, the temporal patterns of vegetative consumption, and monitoring changes to the vegetation community.
Moore, GW, Cleverly, JR & Owens, MK 2008, 'Nocturnal transpiration in riparian Tamarix thickets authenticated by sap flux, eddy covariance and leaf gas exchange measurements', Tree Physiology, vol. 28, no. 4, pp. 521-528.View/Download from: UTS OPUS or Publisher's site
Tamarix chinensis Lour., which is common throughout the southwestern USA, is a phreatophytic riparian tree capable of high water use. We investigated temporal congruence between daily total evapotranspiration (E) estimated from stem sap flux (J(s)) measurements (E(sf)) and eddy covariance (E(cv)), both seasonally and immediately following rain events, and used measurements of leaf-level gas exchange, stem water content and diurnal changes in leaf water potential to track drivers of transpiration. In one study, conducted near the end of the growing season in a pure T. chinensis stand adjacent to the Rio Grande River in central New Mexico, nighttime E(sf) as a proportion of daily E(sf) increased with water availability to a peak of 36.6%. High nighttime E(sf) was associated with underestimates of nighttime E(cv). A second study, conducted in west Texas, beside the Pecos River, investigated the relationships between nighttime J(s) and stem tissue rehydration, on the one hand, and nighttime E, on the other hand. Leaf gas exchange measurements and stomatal impressions suggested that nighttime J(s) was primarily attributed to concurrent transpiration, although there were small overnight changes in stem water content. Both vapor pressure deficit and soil water availability were positively related to nighttime J(s), especially following rainfall events. Thus, both studies indicate that T. chinensis can transpire large amounts at night, a fact that must be considered when attempting to quantify E either by eddy covariance or sap flux methods.
Cleverly, JR, Dahm, CN, Thibault, JR, McDonnell, DE & Coonrod, JE 2006, 'Riparian ecohydrology: Regulation of water flux from the ground to the atmosphere in the Middle Rio Grande, New Mexico', Hydrological Processes, vol. 20, no. 15, pp. 3207-3225.View/Download from: UTS OPUS or Publisher's site
During the previous decade, the south-western United States has faced declining water resources and escalating forest fires due to long-term regional drought. Competing demands for water resources require a careful accounting of the basin water budget. Water lost to the atmosphere through riparian evapotranspiration (ET) is believed to rank in the top third of water budget depletions. To better manage depletions in a large river system, patterns of riparian ET must be better understood. This paper provides a general overview of the ecological, hydrological, and atmospheric issues surrounding riparian ET in the Middle Rio Grande (MRG) of New Mexico. Long-term measurements of ET, water table depth, and micro-meteorological conditions have been made at sites dominated by native cottonwood (Populus deltoides) forests and non-native saltcedar (Tamarix chinensis) thickets along the MRG. Over periods longer than one week, groundwater and leaf area index (LAI) dynamics relate well with ET rates. Evapotranspiration from P. deltoides forests was unaffected by annual drought conditions in much of the MRG where the water table is maintained within 3 m of the surface. Evapotranspiration from a dense Tamarix chinensis thicket did not decline with increasing groundwater depth; instead, ET increased by 50%, from 6 mm/day to 9 mm/day, as the water table receded at nearly 7 cm/day.
Nagler, PL, Cleverly, JR, Glenn, E, Lampkin, D, Huete, A & Zhengming, W 2005, 'Predicting riparian evapotranspiration from MODIS vegetation indices and meteorological data', Remote Sensing Of Environment, vol. 94, no. 1, pp. 17-30.View/Download from: UTS OPUS or Publisher's site
A vegetation index (VI) model for predicting evapotranspiration (ET) from data from the Moderate Resolution Imaging Spectrometer (MODIS) on the EOS-1 Terra satellite and ground meteorological data was developed for riparian vegetation along the Middle Rio Grande River in New Mexico. Ground ET measurements obtained from eddy covariance towers at four riparian sites were correlated with MODIS VIs, MODIS land surface temperatures (LSTs), and ground micrometeorological data over four years. Sites included two saltcedar (Tamarix ramosissima) and two Rio Grande cottonwood (Populus deltoides ssp. Wislizennii) dominated stands. The Enhanced Vegetation Index (EVI) was more closely correlated (r=0.76) with ET than the Normalized Difference Vegetation Index (NDVI; r=0.68) for ET data combined over sites and species. Air temperature (Ta) measured over the canopy from towers was the meteorological variable that was most closely correlated with ET (r=0.82). MODIS LST data at 1- and 5-km resolutions were too coarse to accurately measure the radiant surface temperature within the narrow riparian corridor; hence, energy balance methods for estimating ET using MODIS LSTs were not successful. On the other hand, a multivariate regression equation for predicting ET from EVI and Ta had an r2=0.82 across sites, species, and years. The equation was similar to VIET models developed for crop species. The finding that ET predictions did not require species-specific equations is significant, inasmuch as these are mixed vegetation zones that cannot be easily mapped at the species level.
Nagler, PL, Scott, RL, Westenburg, C, Cleverly, JR, Glenn, E & Huete, A 2005, 'Evapotranspiration on western U.S. rivers estimated using the Enhanced Vegetation Index from MODIS and data from eddy covariance and Bowen ratio flux towers', Remote Sensing Of Environment, vol. 97, no. 3, pp. 337-351.View/Download from: UTS OPUS or Publisher's site
We combined remote sensing and in-situ measurements to estimate evapotranspiration (ET) from riparian vegetation over large reaches of western U.S. rivers and ET by individual plant types. ET measured from nine flux towers (eddy covariance and Bowen ratio) established in plant communities dominated by five major plant types on the Middle Rio Grande, Upper San Pedro River, and Lower Colorado River was strongly correlated with Enhanced Vegetation Index (EVI) values from the Moderate Resolution Imaging Spectrometer (MODIS) sensor on the NASA Terra satellite. The inclusion of maximum daily air temperatures (Ta) measured at the tower sites further improved this relationship. Sixteen-day composite values of EVI and Ta were combined to predict ET across species and tower sites (r2 = 0.74); the regression equation was used to scale ET for 20002004 over large river reaches with Ta from meteorological stations. Measured and estimated ET values for these river segments were moderate when compared to historical, and often indirect, estimates and ranged from 851874 mm yr- 1. ET of individual plant communities ranged more widely. Cottonwood (Populus spp.) and willow (Salix spp.) stands generally had the highest annual ET rates (11001300 mm yr- 1), while mesquite (Prosopis velutina) (4001100 mm yr- 1) and saltcedar (Tamarix ramosissima) (3001300 mm yr- 1) were intermediate, and giant sacaton (Sporobolus wrightii) (500800 mm yr- 1) and arrowweed (Pluchea sericea) (300700 mm yr- 1) were the lowest. ET rates estimated from the flux towers and by remote sensing in this study were much lower than values estimated for riparian water budgets using crop coefficient methods for the Middle Rio Grande and Lower Colorado River.
Shafroth, PB, Cleverly, JR, Dudley, T, Taylor, JP, Riper, IIICV, Weeks, EP & Stuart, JN 2005, 'Control of Tamarix in the Western United States: Implications for Water Salvage, Wildlife Use, and Riparian Restoration', Environmental Management, vol. 35, no. 3, pp. 231-246.View/Download from: UTS OPUS or Publisher's site
Non-native shrub species in the genus Tamarix (saltcedar, tamarisk) have colonized hundreds of thousands of hectares of floodplains, reservoir margins, and other wetlands in western North America. Many resource managers seek to reduce saltcedar abundance and control its spread to increase the flow of water in streams that might otherwise be lost to evapotranspiration, to restore native riparian (streamside) vegetation, and to improve wildlife habitat. However, increased water yield might not always occur and has been substantially lower than expected in water salvage experiments, the potential for successful revegetation is variable, and not all wildlife taxa clearly prefer native plant habitats over saltcedar. As a result, there is considerable debate surrounding saltcedar control efforts. We review the literature on saltcedar control, water use, wildlife use, and riparian restoration to provide resource managers, researchers, and policy-makers with a balanced summary of the state of the science. To best ensure that the desired outcomes of removal programs are met, scientists and resource managers should use existing information and methodologies to carefully select and prioritize sites for removal, apply the most appropriate and cost-effective control methods, and then rigorously monitor control efficacy, revegetation success, water yield changes, and wildlife use.
Cleverly, JR, Dahm, CN, Thibault, JR, Gilroy, DJ & Coonrod, JE 2002, 'Seasonal estimates of actual evapo-transpiration from Tamarix ramosissima stands using three-dimensional eddy covariance', Journal Of Arid Environments, vol. 52, no. 2, pp. 181-197.View/Download from: UTS OPUS or Publisher's site
This study addresses the pattern of evapo-transpiration (ET) throughout the growing season forTamarix ramosissima between regularly flooded and unflooded sites. Spatial and temporal ET patterns along the Middle Rio Grande demonstrated considerable variability. ET at the unflooded site was 61% of ET at the flooded site, totaling 74 and 122 cm year-1 at the unflooded and flooded sites, respectively. The seasonal coefficient of variability was 37% and 38% at the flooded and unflooded sites, respectively. Spatial variability was 39%. Determining ET patterns with respect to the spatial, ecological and temporal setting improves riparian zone ET depletion predictions.
Dahm, CN, Cleverly, JR, Coonrod, JE, Thibault, JR, McDonnell, DE & Gilroy, DJ 2002, 'Evapotranspiration at the land/water interface in a semi-arid drainage basin', Freshwater Biology, vol. 47, no. 4, pp. 831-843.View/Download from: Publisher's site
Evapotranspiration (ET) is a major source of water depletion from riverine systems in arid and semiarid climates. Water budgets have produced estimates of total depletions from riparian vegetation ET for a 320-km reach of the Middle Rio Grande, New Mexico, U.S.A., that have ranged from 20 to 50% of total depletions from the river. 2. Tower-based micrometeorological measurements of riparian zone ET throughout the growing season using three-dimensional eddy covariance provided high quality estimates of ET at the stand scale. 3. A dense stand of salt cedar (111122 cm year1) and a mature cottonwood (Populus deltoides ssp. wislizenia Eckenwelder) stand with an extensive understory of salt cedar (Tamaria ramosissima Ledeb) and Russian olive (Eleagnus angustifolia L.) (123 cm year1) had the highest rates of annual ET. A mature cottonwood stand with a closed canopy had intermediate rates of ET (98 cm year1). A less dense salt cedar stand had the lowest rates of ET (7476 cm year1). 4. Summer leaf area index (LAI) measurements within the four stands were positively correlated with daily ET rates. LAI measurements throughout the growing season coupled to riparian vegetation classification is a promising method for improving riverine corridor estimates of total annual riparian zone ET along a reach of river. 5. Combining recent estimates of the extent of riparian vegetation along the 320 km length of the Middle Rio Grande, from Landsat 7 imagery with annual growing season measurements of ET at the four riparian stands yields a first-order riverine corridor estimate of total riparian zone ET of 150250 × 106 m3 year1. This is approximately 2033% of total estimated depletions along this reach of river.
Devitt, DA, Sala, A, Smith, SD, Cleverly, JR, Shaulis, LK & Hammett, R 1998, 'Bowen ratio estimates of evapotranspiration for Tamarix ramosissima stands on the Virgin River in southern Nevada', Water resources research, vol. 34, no. 9, pp. 2407-2414.View/Download from: Publisher's site
A Bowen ratio energy balance was conducted over a Tamarix ramosissima (saltcedar) stand growing in a riparian corridor along the Virgin River in southern Nevada. Measurements in two separate years were compared and contrasted on the basis of changes in growing conditions. In 1994, a drought year, record high temperatures, dry winds, and a falling water table caused partial wilt of outer smaller twigs in the canopy of many trees in the stand around the Bowen tower. Subsequently, evapotranspiration (ET) estimates declined dramatically over a 60-day period (11 mm d-1 to <1 mm d-1). In 1995, the Virgin River at the Bowen tower area changed its course, hydrologically isolating the Tamarix stand in the vicinity of the tower. In 1996, a 25% canopy loss was visually estimated for the Tamarix growing in the area of the tower. Higher soil temperatures relative to air temperatures were recorded in 1996 in response to this loss in canopy. With a more open canopy, thermally induced turbulence was observed in 1996. On day 160 of 1996, a 28°C rise over a 9-hour period was correlated with increased wind speeds of greater than 4 m s-1. Subsequently, higher ET estimates were made in 1996 compared to 1994 (145 cm versus 75 cm).
Smith, SD, Devitt, DA, Sala, A, Cleverly, JR & Busch, DE 1998, 'Water relations of riparian plants from warm desert regions', Wetlands, vol. 18, no. 4, pp. 687-696.View/Download from: UTS OPUS or Publisher's site
Riparian plants have been classified as "drought avoiders" due to their access to an abundant subsurface water supply. Recent water-relations research that tracks water sources of riparian plants using the stable isotopes of water suggests that many plants of the riparian zone use ground water rather than stream water and not all riparian plants are obligate phreatophytes (dependent on ground water as a moisture source) but may occasionally be dependent on unsaturated soil moisture sources. A more thorough understanding of riparian plant-water relations must include water-source dynamics and how those dynamics vary over both space and time. Many rivers in the desert Southwest have been invaded by the exotic shrub Tamarix ramosissima (saltcedar. Our studies of Tamarix invasion into habitats formerly dominated by native riparian forests of primarily Populus and Sallix have shown that Tamarix successfully invades these habitats because of its (I) greater tolerance to water stress and salinity, (2) status as a facultative, rather than obligate, phreatophyte and, therefore, its ability to recover from droughts and periods of ground-water drawdown, and (3! superior regrowth after fire. Analysis of water-loss rates indicate that Tamarix-dominated stands can have extremely high evapotranspiration rates when water tables are high but not necessarily when water tables are lower. Tamarix has leaf-level transpiration rates that are comparable to native species, whereas sap-flow rates per unit sapwood area are higher than in natives, suggesting that Tamarix maintains higher leaf area than can natives, probably due to its greater water stress tolerance. Tamarix desiccates rind salinizes floodplains, due to its salt exudation and high transpiration rates, and may also accelerate fire cycles, thus predisposing these ecosystems to further loss of native taxa.
Cleverly, JR, Smith, SD, Sala, A & Devitt, DA 1997, 'Invasive capacity of Tamarix ramosissima in a Mojave Desert Floodplain: the role of drought', Oecologia, vol. 111, no. 1, pp. 12-18.View/Download from: UTS OPUS or Publisher's site
Tamarix ramosissima (Tamaricaceae) is a woody phreatophyte that has invaded thousands of hectares of floodplain habitat in the southwestern U.S. In this study, we examined the response of gas exchange and stem sap flow of Tamarix and three co-occurring native phreatophytes (Pluchea sericea (Asteraceae), Prosopis pubescens (Fabaceae) and Salix exigua (Salicaceae)) to drought conditions in an early successional floodplain community in the Mojave Desert of southern Nevada. In an analysis of a size/age series of each species across the whole floodplain (both mature and successional stands), stem growth rate was lowest for Tamarix. However, along the same successional chronosequence, Tamarix came to dominate the 50+ year old stands with dense thickets of high stem density. Xylem sap flow, when expressed on a sapwood area basis, was highest in Tamarix under early drought conditions, but comparable between the four species toward the end of the summer dry season. Multivariate analysis of the gas exchange data indicated that the four species differentiated based on water use under early drought conditions and separated based on plant water potential and leaf temperature (indices of drought effects) at the end of the summer dry season. This analysis suggests that the invasive Tamarix is the most drought tolerant of the four species, whereas Salix transpires the most water per unit leaf surface area and is the least tolerant of seasonal water stress.
Devitt, DA, Piorkowski, JM, Smith, SD, Cleverly, JR & Sala, A 1997, 'Plant water relations of Tamarix ramosissima in response to the imposition and alleviation of soil moisture stress', Journal Of Arid Environments, vol. 36, no. 3, pp. 527-540.View/Download from: UTS OPUS or Publisher's site
The effect of an extended drydown on the water relations ofTamarix ramosissima(saltcedar), a desert phreatophyte, was investigated along the floodplain of the Virgin River (southern Nevada) during a hot dry summer period. Seedlings ofTamarixwere grown in lysimeters (120 cm depth, 51 cm radius) positioned along a gradient from the desert's edge to the interior of the stand and monitored for growth and evapo-transpiration over a 2-year period prior to this study. Water tables were maintained at approximately 60 cm during the evapo-transpiration study by applying weekly irrigation directly to the water table via piezometers. At the end of the 2-year period, three lysimeters were selected for a drydown experiment (desert's edge, river's edge, open stand). On 7 July 1995 all irrigation was terminated for a 29-day period. After the drydown period was over, irrigation was applied for an 18-day period to re-establish water table depths. Sapflow (transpiration) was monitored during the entire 47-day period (drydown, wetup) with stem flow gauges, soil moisture with time domain reflectometry, and plant water relations with a steady state porometer and pressure chamber. Results indicated that sapflow decreased significantly as water tables and stored soil water declined. Daily sapflow totals on a leaf area basis were higher for the plant growing along the river's edge, with midday hourly values significantly higher when a water table was present.
Sovocool, KA, Cleverly, JR, Neuman, DS & Smith, SD 1997, 'Growth, allocation and water stress in 2-year-old seedling communities following competitive release in a Mojave Desert floodplain', Plant Physiology, vol. 114, no. 3, pp. 1172-1172.
Barker, DF, Cieverly, J & Fain, PR 1992, 'Two CA-dinucleotide polymorphisms at the COL4A5 (alport syndrome) gene in XQ22', Nucleic Acids Research, vol. 20, no. 4, pp. 929-929.View/Download from: Publisher's site
BARKER, DF, CLEVERLY, J & FAIN, PR 1992, '2 CA-DINUCLEOTIDE POLYMORPHISMS AT THE COL4A5 (ALPORT SYNDROME) GENE IN XQ22', NUCLEIC ACIDS RESEARCH, vol. 20, no. 4, pp. 929-929.View/Download from: Publisher's site
Haverd, V, Smith, B, Raupach, M, Briggs, P, Nieradzik, L, Beringer, J, Hutley, L, Trudinger, CM & Cleverly, J, 'Coupling carbon allocation with leaf and root phenology predicts tree-grass partitioning along a savanna rainfall gradient', Biogeosciences Discussions, vol. 12, no. 19, pp. 16313-16357.View/Download from: UTS OPUS or Publisher's site
The relative complexity of the mechanisms underlying savanna ecosystem dynamics, in comparison to other biomes such as temperate and tropical forests, challenges the representation of such dynamics in ecosystem and Earth system models. A realistic representation of processes governing carbon allocation and phenology for the two defining elements of savanna vegetation (namely trees and grasses) may be a key to understanding variations in tree/grass partitioning in time and space across the savanna biome worldwide. Here we present a new approach for modelling coupled phenology and carbon allocation, applied to competing tree and grass plant functional types. The approach accounts for a temporal shift between assimilation and growth, mediated by a labile carbohydrate store. This is combined with a method to maximise long-term net primary production (NPP) by optimally partitioning plant growth between fine roots and (leaves + stem). The computational efficiency of the analytic method used here allows it to be uniquely and readily applied at regional scale, as required, for example, within the framework of a global biogeochemical model. <br><br> We demonstrate the approach by encoding it in a new simple carbon/water cycle model that we call HAVANA (Hydrology and Vegetation-dynamics Algorithm for Northern Australia), coupled to the existing POP (Population Orders Physiology) model for tree demography and disturbance-mediated heterogeneity. HAVANA-POP is calibrated using monthly remotely-sensed fraction of absorbed photosynthetically active radiation (fPAR) and eddy-covariance-based estimates of carbon and water fluxes at 5 tower sites along the Northern Australian Tropical Transect (NATT), which is characterized by large gradients in rainfall and wildfire disturbance. The calibrated model replicates observed gradients of fPAR, tree leaf area index, basal area and foliage projective cover along the NATT. The model behaviour emerges from complex feed-...
Cleverly, JR, Thibault, JR & Dahm, CN 2007, 'Ecohydrology of the middle Rio Grande riparian zone in Mexico', Denver.
Cleverly, JR 2006, 'Evapotranspiration: long-term studies of ecohydrology and biometeorology along the Middle Rio Grande', Mexico.
Cleverly, JR 2001, 'Full season estimates of evapotranspiration from mature cottonwood and saltcedar ecosystems along the Middle Rio Grande', Albuquerque, NM.
Cleverly, JR 2002, 'The impacts of exotic water using plants: Tamarisk', Arizona.
Cleverly, JR, Dahm, CN & Thibault, JR 2002, 'Water use by Middle Rio Grande phreatophytes: monitoring the contributions of Russian olive, saltcedar and cottonwood', New Mexico.
Cleverly, JR, Thibault, JR, Bailey, N & McDonnell, DE 2002, 'Evapotranspiration depletions from the Middle Rio Grande water budget: multiyear monitoring of micrometeorology, groundwater, and soil characteristics', Socorro, NM.
Allred Coonrod, JE, McDonnell, D, Dahm, CN, Cleverly, JR & Thibault, JR 2001, 'Determining Evapotranspiration Rates in the Middle Rio Grande Bosque: 3-D Eddy Covariance and Remote Sensing Techniques', Proceedings of the 2001 Wetlands Engineering and River Restoration Conference, pp. 353-370.
Currently, annual rates of actual evapotranspiration (ET) in native and non-native riparian forests in semi-arid landscapes are poorly known. In addition, the effects of flooding, or the removal of flooding through flow regulation, on riparian ecosystem ET is also not well understood. Both ground-based and remote sensing techniques are used to estimate ET along the Middle Rio Grande corridor. Ground based climatic data are collected using four instrumentation towers installed in representative ecosystems. The 3-D Eddy Covariance method gives more accurate estimates of ET than were previously known. Landsat imagery, along with ground estimates of leaf area index (LAI), will be used to scale the estimates to the entire corridor.
Cleverly, JR 2001, 'Evaluation of 3-dimensional eddy covariance and other methods of collecting daily, seasonal and interannual evapotranspiration data from saltcedar (Tamarix ramosissima) and Tio Grande Cottonwood (Populus deltoides var. wislizeni) Forests', New Mexico.
Dahm, CN, Cleverly, JR, Coonrod, JE, Thibault, JR, McDonnell, DE & Gilroy, DJ 2001, 'Evapotranspiration at the land/water interface in a semi-arid drainage basin', Ascona, Switzerland.
Cleverly, JR 2000, 'Evapotranspiration from the Middle Rio Grande', New Mexico.
Cleverly, JR 1999, 'Water relations, stress physiology and ecology of plants in the Mojave and Chihuahuan Deserts: Sevilleta NWR (NM), Middle Rio Grande (NM) and Lower Virgin River (NV)', New Mexico.
Cleverly, JR, Sovocool, KA, Smith, SD, Sala, A, Devitt, DA, Shaulis, LK & Busch, DE 1998, 'Stress physiology and competition between the exotic Tamarix ramosissima and co-occuring native phreatophytes in a short-term recovering Mojave Desert floodplain', New Mexico.
Smith, SD, Sala, A, Devitt, DA & Cleverly, JR 1995, 'Evapotranspiration from a saltcedar-dominated desert floodplain: A scaling approach', PROCEEDINGS: SHRUBLAND ECOSYSTEM DYNAMICS IN A CHANGING ENVIRONMENT, Symposium on Shrubland Ecosystem Dynamics in a Changing Environment, US DEPT AGR, FOREST SERV INTERMOUNTARIN RESEARCH STN, LAS CRUCES, NM, pp. 199-204.
Cleverly, J OzFlux: Australian and New Zealand Flux Research Monitoring Network 2011, Alice Springs Mulga OzFlux site, TERN OzFlux: Australian and New Zealand Flux Research and Monitoring Network.
Cleverly, J & Isaac, P 2014, 'OzFluxQC Simulator'.
Cleverly, J 2013, 'QCPlus'.
Cleverly, J 2013, 'Ti Tree East OzFlux Site'.
OzFlux: Australian and New Zealand Flux Research and Monitoring Network
Isaac, P & Cleverly, J 2012, 'OzFlux QC'.
Cleverly, J 2011, 'Alice Springs Mulga OzFlux site'.
OzFlux: Australian and New Zealand Flux Research and Monitoring Network
Isaac, P & Cleverly, J 2011, 'OzFlux QC', CSIRO, Canberra.