Global distributions and environmental correlates of community leaf length and width in forests

Leaf length and width are key dimensions of tree leaf size and can influence leaf boundary-layer development and leaf-environment heat exchange. However, their global patterns and environmental correlates remain poorly understood. By integrating tree leaf traits and community data, we mapped community leaf length and width and identified their environmental correlates in global forests. Both community leaf length and width decreased toward higher latitudes, although leaf width showed an additional peak at mid-latitudes. These asynchronous patterns contributed to geographic variation in leaf shape, with more elongated leaves in tropical and boreal forests and relatively rounder leaves in temperate forests. Soil variables and mean annual temperature were the main correlates of leaf length, whereas leaf width was mainly associated with temperature. Our results reveal distinct environmental correlates of community leaf length and width, highlight the value of multiple leaf dimensions for predicting forest distributions and function, and identify tropical regions where additional trait data are needed to reduce uncertainty.