Trait but not species convergence during succession of sub-alpine meadows in the eastern Qinghai-Tibetan Plateau, China

Background/Question/Methods

The processes that determine community assembly vary across a large variety of communities and are still far from being understood. Patterns of functional trait diversity along successional gradients may reflect the importance of the combined effects of different ecological processes and thus provide better insight into community assembly. We investigated the changes of species composition, trait composition and functional trait diversity in a series of sub-alpine meadow plant communities along a successional gradient in the eastern Qinghai-Tibetan Plateau, China. Then we evaluated the contribution of multiple ecological processes (particularly species interactions and habitat filtering) to community assembly using a null model approach and by partitioning the environmental and spatial components of functional composition.

Results/Conclusions

We found that functional diversity increased and, while trait composition and dissimilarity in trait composition among within-meadow quadrats decreased, along the successional gradient. We also found evidence for weak divergence at the species level. Both habitat filtering and niche differentiation affect trait composition, with the dominance of niche differentiation. Moreover, functional diversity appeared to saturate near the 10m scale, after showing a significant increase at smaller scales.  We conclude that trait convergence rather than of species convergence explains community assembly along all the successional gradients. Succession is a deterministic process at the niche level, accompanied by historical effects at the species level. Within meadows, biotic processes (weak competitor exclusion) instead of abiotic processes appear to dominate the assembly of these sub-alpine meadows. Our results demonstrate the ability of functional trait diversity and functional composition in inferring the successional direction and the mechanisms of community assembly in communities recovering from disturbance.