Leaf-trait variation explained by the hypothesis that plants maximize their canopy carbon export over the lifespan of leaves

• Published in: Tree physiology Vol. 31; no. 9; pp. 1007 - 1023
• Main Authors: McMurtrie, Ross E, Dewar, Roderick C
• Format: Journal Article
• Language: English
• Published: Canada Oxford University Press 01.09.2011
• Subjects: anatomy & histology; Biological Evolution; canopy; carbon; Carbon - metabolism; Carbon Dioxide; Carbon Dioxide - metabolism; Carbon Sequestration; Climate Change; convergent evolution; environmental factors; Greenhouse Effect; leaf area; leaf development; leaves; light intensity; longevity; metabolism; Models, Biological; nitrogen; Nitrogen - metabolism; nitrogen content; photosynthesis; Photosynthesis - physiology; physiology; Plant Leaves; Plant Leaves - anatomy & histology; Plant Leaves - metabolism; Trees; Trees - anatomy & histology; Trees - metabolism; nitrogen-use efficiency; optimality; leaf-area index; canopy carbon export; forest model; maximization; photosynthesis model; leaf-trait relationships; plant carbon-nitrogen economy; global change; specific leaf area; optimal plant function; leaf lifespan
• ISSN: 0829-318X; 1758-4469; 1758-4469
• DOI: 10.1093/treephys/tpr037

Measured values of four key leaf traits (leaf area per unit mass, nitrogen concentration, photosynthetic capacity, leaf lifespan) co-vary consistently within and among diverse biomes, suggesting convergent evolution across species. The same leaf traits co-vary consistently with the environmental conditions (light intensity, carbon-dioxide concentration, nitrogen supply) prevailing during leaf development. No existing theory satisfactorily explains all of these trends. Here, using a simple model of the carbon–nitrogen economy of trees, we show that global leaf-trait relationships and leaf responses to environmental conditions can be explained by the optimization hypothesis (MAXX) that plants maximize the total amount of carbon exported from their canopies over the lifespan of leaves. Incorporating MAXX into larger-scale vegetation models may improve their consistency with global leaf-trait relationships, and enhance their ability to predict how global terrestrial productivity and carbon sequestration respond to environmental change.