Leaf nitrogen from first principles: field evidence for adaptive variation with climate

摘要: Abstract. Nitrogen content per unit leaf area (Narea) is a key variable in plant functional ecology and biogeochemistry. Narea comprises structural component, which scales with mass (LMA), metabolic Rubisco capacity. The co-ordination hypothesis, as implemented LPJ related global vegetation models, predicts that capacity should be directly proportional to irradiance but decrease increases ci : ca temperature because the amount of required achieve given assimilation rate declines both. We tested these predictions using LMA, δ13C, N measurements on complete species assemblages sampled at sites north–south transect from tropical temperate Australia. Partial effects mean canopy irradiance, annual temperature, (from δ13C) were all significant their directions magnitudes line predictions. Over 80 % variance community-mean (ln) was accounted for by predictors plus LMA. Moreover, could decomposed into two components, one LMA (slightly steeper N-fixers), other predicted hypothesis. Trait gradient analysis revealed perfectly plastic, while turnover contributed about half variation Narea. Interest has surged methods predict continuous leaf-trait environmental factors, order improve ecosystem models. Coupled carbon–nitrogen models require method more realistic than widespread assumptions photosynthetic capacity, and/or (and capacity) are determined supply soil. Our results indicate useful degree predictability, combination – themselves part environmentally activity, local growing conditions. This finding consistent plant-centred approach modelling, emphasizing adaptive regulation traits. Models account biodiversity will also need partition community-level trait components due phenotypic plasticity genotypic differentiation within vs. progressive replacement, along gradients. suggests evenly split between modes.