Stem diameter growth rates in a fire‐prone savanna correlate with photosynthetic rate and branch‐scale biomass allocation, but not specific leaf area

Wright, Ian J., Cooke, Julia, Cernusak, Lucas A., Hutley, Lindsay B., Scalon, Marina C., Tozer, Wade C., and Lehmann, Caroline E.R. (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, 44 (2). pp. 339-350.

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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 (Asat), 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 Asat. Together, these two traits accounted for up to 80% of interspecific variation in adult GR, and 41% of sapling GR. Asat 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.

Item ID: 57906
Item Type: Article (Research - C1)
ISSN: 1442-9993
Keywords: leaf, leaf economic spectrum, plant functional traits, relative growth rate, specific leaf area, stem allocation
Copyright Information: © 2018 Ecological Society of Australia
Funders: Macquarie University (MQ), Australian Research Council (ARC)
Projects and Grants: ARC DP120103284
Date Deposited: 10 Apr 2019 07:36
FoR Codes: 30 AGRICULTURAL, VETERINARY AND FOOD SCIENCES > 3007 Forestry sciences > 300703 Forest ecosystems @ 50%
31 BIOLOGICAL SCIENCES > 3108 Plant biology > 310806 Plant physiology @ 50%
SEO Codes: 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960806 Forest and Woodlands Flora, Fauna and Biodiversity @ 100%
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