The Temporal Turnover Of Plant Community Composition Along An Environmental Gradient:the Role Of Facilitation

Temporal turnover reflects the compositional changes of the ecological communities through time, i.e. the dissimilarity between different time points in the same ecological community. The greater the dissimilarity is, the faster temporal turnover of the ecological communities. Temporal turnover occurs in all ecological communities, so it is one of the basic properties of natural communities and an important part of the ecological theory.The lack of high-quality long-term data has greatly hindered the full exploration of temporal turnover in biological communities and underlying mechanisms. Meanwhile, it has been demonstrated that the interplay between negative and positive interactions simultaneously shapes community structures. However, few studies have attempted to test the effect of facilitation on temporal compositional changes. Using an individual-based model incorporating plant strategies, we explored the patterns of temporal turnover along an environmental gradient and assessed the role of facilitation.We found that under severe environmental conditions, facilitation resulted in higher species richness than the models without facilitation. The results further showed that along the environmental severity gradient, the simulated community displayed a three-phase temporal turnover:the Bray-Curtis similarity values firstly decreased, then increased, and lastly decreased again. The effect of facilitation on temporal compositional changes also depended on the position of the considered community along the environmental severity gradient. The mean population size explained the temporal turnover along the gradient and the severity-dependent role of facilitation, which showed a nonlinear, asymptotic relationship with the rate of temporal variability.The present simulation work contributes to our understanding of factors driving temporal turnover, and sheds light on the consequences of ongoing climate change on community assembly and ecosystem services.