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Ecol Lett. 2014 Jan;17(1):82-91. doi: 10.1111/ele.12211. Epub 2013 Nov 11.

Balancing the costs of carbon gain and water transport: testing a new theoretical framework for plant functional ecology.

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Department of Biological Sciences, Macquarie University, North Ryde, NSW, 2109, Australia; AXA Chair of Biosphere and Climate Impacts, Department of Life Sciences and Grantham Institute for Climate Change, Imperial College, Silwood Park, Ascot, SL5 7PY, UK.


A novel framework is presented for the analysis of ecophysiological field measurements and modelling. The hypothesis 'leaves minimise the summed unit costs of transpiration and carboxylation' predicts leaf-internal/ambient CO2 ratios (ci /ca ) and slopes of maximum carboxylation rate (Vcmax ) or leaf nitrogen (Narea ) vs. stomatal conductance. Analysis of data on woody species from contrasting climates (cold-hot, dry-wet) yielded steeper slopes and lower mean ci /ca ratios at the dry or cold sites than at the wet or hot sites. High atmospheric vapour pressure deficit implies low ci /ca in dry climates. High water viscosity (more costly transport) and low photorespiration (less costly photosynthesis) imply low ci /ca in cold climates. Observed site-mean ci /ca shifts are predicted quantitatively for temperature contrasts (by photorespiration plus viscosity effects) and approximately for aridity contrasts. The theory explains the dependency of ci /ca ratios on temperature and vapour pressure deficit, and observed relationships of leaf δ(13) C and Narea to aridity.


Aridity; nitrogen; optimality; photosynthesis; plant functional traits; stable isotopes; stomatal conductance; temperature; transpiration; viscosity

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