Almost all plant species interact with one or more symbioses somewhere within their distribution range. Bringing together plant trait data and growth responses to symbioses spanning 552 plant species, we provide for the first time on a large scale (597 studies) a quantitative synthesis on plant performance differences between eight major types of symbiosis, including mycorrhizas, N-fixing bacteria, fungal endophytes and ant-plant interactions. Frequency distributions of plant growth responses varied considerably between different types of symbiosis, in terms of both mean effect and 'risk', defined here as percentage of experiments reporting a negative effect of symbiosis on plants. Contrary to expectation, plant traits were poor predictors of growth response across and within all eight symbiotic associations. Our analysis showed no systematic additive effect when a host plant engaged in two functionally different symbioses. This synthesis suggests that plant species' ecological strategies have little effect in determining the influence of a symbiosis on host plant growth. Reliable quantification of differences in plant performance across symbioses will prove valuable for developing general hypotheses on how species become engaged in mutualisms without a guarantee of net returns.
Wright, IJ, Cooke, J, Cernusak, LA, Hutley, LB, Scalon, MC, Tozer, WC & Lehmann, CER 2019, 'Stem diameter growth rates in a fire-prone savanna correlate with photosynthetic rate and branch-scale biomass allocation, but not specific leaf area', Austral Ecology, vol. 44, no. 2, pp. 339-350.View/Download from: Publisher's site
© 2018 Ecological Society of Australia Plant growth rates strongly determine ecosystem productivity and are a central element of plant ecological strategies. For laboratory and glasshouse-grown seedlings, specific leaf area (SLA; ratio of leaf area to mass) is a key driver of interspecific variation in growth rate (GR). Consequently, SLA is often assumed to drive GR variation in field-grown adult plants. However, there is an increasing evidence that this is not the general case. This suggests that GR – SLA relationships (and perhaps those for other traits) may vary depending on the age or size of the plants being studied. Here we investigated GR – trait relationships and their size dependence among 17 woody species from an open-canopy, fire-prone savanna in northern Australia. We tested the predictions that SLA and stem diameter growth rate would be positively correlated in saplings but unrelated in adults while, in both age classes, faster-GR species would have higher light-saturated photosynthetic rate (A sat ), higher leaf nutrient concentrations, higher branch-scale biomass allocation to leaf versus stem tissues and lower wood density (WD). SLA showed no relationship to stem diameter GR, even in saplings, and the same was true of leaf N and P concentrations, and WD. However, branch-scale leaf:stem allocation was strongly related to GR in both age groups, as was A sat . Together, these two traits accounted for up to 80% of interspecific variation in adult GR, and 41% of sapling GR. A sat is rarely measured in field-based GR studies, and this is the first report of branch-scale leaf:stem allocation (analogous to a benefit:cost ratio) in relation to plant growth rate. Our results suggest that we may yet find general trait-drivers of field growth rates, but SLA will not be one.
Gleason, SM, Stephens, AEA, Tozer, WC, Blackman, CJ, Butler, DW, Chang, Y, Cook, AM, Cooke, J, Laws, CA, Rosell, JA, Stuart, SA & Westoby, M 2018, 'Shoot growth of woody trees and shrubs is predicted by maximum plant height and associated traits', FUNCTIONAL ECOLOGY, vol. 32, no. 2, pp. 247-259.View/Download from: Publisher's site
Tozer, WC, Hackell, D, Miers, DB & Silvester, WB 2005, 'Extreme isotopic depletion of nitrogen in New Zealand lithophytes and epiphytes; the result of diffusive uptake of atmospheric ammonia?', OECOLOGIA, vol. 144, no. 4, pp. 628-635.View/Download from: Publisher's site
McQueen, J, Tozer, W & Clarkson, B 2005, 'Consequences of alien N2-fixers on vegetation succession in New Zealand'.