Environment shapes tree community traits in China's forests

Question Environmental filtering plays an important role in plant community assembly. To what extent does the broad-scale environment influence the functional composition of woody plants in China's forests? Is there stronger trait convergence under harsher environmental conditions? Location China. Methods We characterized community traits and their relationships to climate and soil, using a data set with 1312 plots of tree communities composed of 1591 tree species and 10 functional traits across China. Using quadratic models, we explored how community traits change with different environmental factors. Results Trait spectra at the species level and the community level were significantly correlated, and the first two principal components captured 74.5% of the variation in community-weighted mean traits. The trait spectra showed a clear elevational pattern and varied along climate and soil gradients. Compared with random expectations, the multi-trait functional diversity showed a divergence pattern on poor soils at the plot scale. Conclusions Two well-known dimensions, the leaf economics spectrum and size-related spectrum, could be extended from the species level to the community level. Environment, especially climate conditions, drives the trait spectra and their elevational patterns at the broad scale, indicating environmental filtering might shape the trait composition of tree communities in China. However, stronger environmental filtering does not occur under harsher environmental conditions.