Role of Annual Leaf Carbon Balance in the Distribution of Plant Species along an Elevational Gradient

Physiological responses to water stress were determined under laboratory conditions for eight woody perennial species occupying different positions along a moisture gradient in the Santa Catalina Mountains of Arizona. Annual leaf carbon balances were calculated over a range of elevations from net photosynthesis and dark respiration responses to leaf water potential (LWP), the dependence of LWP on soil water potential (SWP), and yearly patterns of SWP. Species ranking in elevations at which annual leaf carbon balances were zero agreed with the ranking of actual lower elevational limits. This integrated measure of the ability of species to acquire carbon in the field was the only physiological response which correctly ranked the species by distribution limit.