Hui Zhang, Han Y.H. Chen, Juyu Lian, Robert John, Ronghua Li, Hui Liu, Wanhui Ye, Frank Berninger, Qing Ye.

For more than a century, community ecologists have been embroiled in arguments about whether deterministic or stochastic processes play the primary role in structuring ecological communities, and whether the relative importance of stochastic (e.g., dispersal limitation) vs. deterministic (e.g., habitat filtering and niche partitioning) processes might be dependent on the spatial scale of investigation. A key tool in attempting to answer this question is to quantify the spatial patterns of functional trait diversity (FD), i.e. the extent to which different kinds of plants are found together. However, few reports are available that use functional traits closely related to plant life history strategies from an entire species-rich community. Here, in a 20-ha species-rich subtropical forest, in which all trees greater than 1 cm in diameter have been mapped, we employ two FD-based tests and one spatial analysis, to quantity patterns of functional traits that are associated with key physiological processes of resource acquisition and drought tolerance at multiple spatial scales. We demonstrate that at relatively small scales, the abiotic environment selects the kind of species that are able to grow, leading to trait convergence. But at relatively large scales, dispersal limitation becomes dominant, causing the weakening of trait convergence, thus highlighting the application of FD patterns in disentangling the scale-dependent ecological processes of community assembly.

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Image caption: Trees in the national reserve of Dinghu Mountain in Guangdong Province, Southern China. Photo provided by authors.