Abstract
Leaf mass per area (Ma), nitrogen content per unit leaf area (Narea), maximum carboxylation capacity (Vcmax) and the ratio of leaf-internal to ambient CO2 partial pressure (χ) are important traits related to photosynthetic function, and they show systematic variation along climatic and elevational gradients. Separating the effects of air pressure and climate along elevational gradients is challenging due to the covariation of elevation, pressure and climate. However, recently developed models based on optimality theory offer an independent way to predict leaf traits and thus to separate the contributions of different controls. We apply optimality theory to predict variation in leaf traits across 18 sites in the Gongga Mountain region. We show that the models explain 59% of trait variability on average, without site- or region-specific calibration. Temperature, photosynthetically active radiation, vapor pressure deficit, soil moisture and growing season length are all necessary to explain the observed patterns. The direct effect of air pressure is shown to have a relatively minor impact. These findings contribute to a growing body of research indicating that leaf-level traits vary with the physical environment in predictable ways, suggesting a promising direction for the improvement of terrestrial ecosystem models.
Highlights
A number of leaf traits are diagnostic of photosynthetic processes
Our analyses focus on four leaf traits: (i) leaf mass per unit area (Ma, g biomass m−2), (ii) the maximum capacity of carboxylation at 25 ◦C (Vcmax25, μmolC m−2 s−1), (iii) the ratio of leaf-internal to ambient CO2 partial pressure (χ, unitless) and (iv) leaf nitrogen content per unit area (Narea, g m−2). The Ma was obtained from the measurements of leaf area and dry weight following standard protocols (Cornelissen et al 2003)
The Narea was mainly controlled by radiation and moisture and covaried with Ma and Vcmax25
Summary
A number of leaf traits are diagnostic of photosynthetic processes. The ratio of leaf-internal to external CO2 (χ ) reflects the stomatal regulation of CO2 uptake, which has to be balanced against water loss (Wang et al 2017b). The maintenance of transpiration involves a carbon cost, in the form of respiration by living parenchyma cells, to maintain active water transport tissues. The maintenance of photosynthetic capacity incurs a substantial carbon cost in the form of leaf respiration to support protein synthesis. Nitrogen is required for both metabolic processes and leaf construction (Lambers and Poorter 1992, Onoda et al 2004). Leaf nitrogen content per unit area (Narea) provides a combined measure of the metabolic and structural costs
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call