资源环境科技发展态势分析平台

Large spatial and temporal gradients in rainfall and temperature occur across Australia. This heterogeneity drives ecological differentiation in vegetation structure and ecophysiology. We examined multiple leaf-scale traits, including foliar Delta C-13 isotope discrimination (Delta C-13), rates of photosynthesis and foliar N concentration and their relationships with multiple climate variables. Fifty-five species across 27 families were examined across eight sites spanning contrasting biomes. Key questions addressed include: (i) Does Delta C-13 and intrinsic water-use efficiency (WUEi) vary with climate at a continental scale? (ii) What are the seasonal and spatial patterns in Delta C-13/WUEi across biomes and species? (iii) To what extent does Delta C-13 reflect variation in leaf structural, functional and nutrient traits across climate gradients? and (iv) Does the relative importance of assimilation and stomatal conductance in driving variation in Delta C-13 differ across seasons? We found that MAP, temperature seasonality, isothermality and annual temperature range exerted independent effects on foliar Delta C-13/WUEi. Temperature-related variables exerted larger effects than rainfall-related variables. The relative importance of photosynthesis and stomatal conductance (g(s)) in determining Delta C-13 differed across seasons: Delta C-13 was more strongly regulated by g(s) during the dry-season and by photosynthetic capacity during the wet-season. Delta C-13 was most strongly correlated, inversely, with leaf mass area ratio among all leaf attributes considered. Leaf N-mass was significantly and positively correlated with MAP during dry- and wet-seasons and with moisture index (MI) during the wet-season but was not correlated with Delta C-13. Leaf P-mass showed significant positive relationship with MAP and Delta C-13 only during the dry-season. For all leaf nutrient-related traits, the relationships obtained for C-13 with MAP or MI indicated that Delta C-13 at the species level reliably reflects the water status at the site level. Temperature and water availability, not foliar nutrient content, are the principal factors influencing Delta C-13 across Australia.