Balancing the costs of carbon gain and water transport: testing a new theoretical framework for plant functional ecology.
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.
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.
I Colin
IC
Prentice
Ning
N
Dong
Sean M
SM
Gleason
Vincent
V
Maire
Ian J
IJ
Wright
D000465:Algorithms; D002245:Carbon Dioxide / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism*; D018526:Plant Transpiration; D010944:Plants / Q000378:metabolism*
D002245:Carbon Dioxide; D009584:Nitrogen
Aridity; nitrogen; optimality; photosynthesis; plant functional traits; stable isotopes; stomatal conductance; temperature; transpiration; viscosity