The Relative Importance of Niche and Neutral Processes for the Community Assembly of Subtropical Karst Forest Communities at Different Spatial Scales

As spatial scale changes, the ecological processes and mechanisms that determine community patterns change. To understand these spatial effects, we established a medium-sized forest plot in an evergreen and deciduous broad-leaved mixed forest in Guilin, Guangxi, southwestern China. Here, we compared the fit of niche and neutral models to the observed species abundance distributions (SADs) at three sampling scales (10 m x 10 m, 20 m x 20 m, 50 m x 50 m). We also performed a PER-SIMPER analysis to further evaluate the relative contribution of niche and neutral processes based on taxon occurrence data. Our results showed that niche-based selection and dispersal-based neutral processes are simultaneously expressed at the 10 m x 10 m and 20 m x 20 m sampling scales. Additionally, dispersal-based neutral processes were predominant at each sampling scale. From these results, we found that the dispersal-based neutral process is the prominent driver for forest community structure in a typical karst forest environment. Ultimately, our work will be useful for future restoration and reconstruction efforts in karst forest communities, showing that environmental heterogeneity, inter-species relationships, and geographic spatial differences should be considered in these efforts.