Effects of negative density dependence and habitat filtering on temporal variation in phylogenetic community structure of seedlings in a mid-subtropical forest

Negative density dependence and habitat filtering are important mechanisms to explain the coexistence of species and the biodiversity patterns of forest communities. Negative density dependence is assumed to enhance phylogenetic α diversity via negative interactions among individuals within a species or among closely related species via competition for similar resources and the sharing of similar pathogens and predators. In contrast, habitat filtering is hypothesized to reduce phylogenetic β diversity within a habitat by selecting for similar resident species that can tolerate the habitat and by eliminating other species. Previous studies focused mainly on testing these two hypotheses by analyzing the spatial patterns of species diversity. Only a handful of studies have examined the temporal variation in phylogenetic community structure. This study attempted to test these two mechanisms by analyzing the temporal variation in community phylogenetic diversity of seedlings(DBH1 cm) in 342 quadrats(1 m×1 m) in a mid-subtropical forest in Gutianshan National Nature Reserve, Zhejiang Province, China. We found that the phylogenetic α diversity of seedling within habitats increased significantly from the year 2006 to 2007. In contrast, the phylogenetic β diversity of seedlings within habitats declined significantly over time. These results suggested that negative density dependence and habitat filtering jointly determined the phylogenetic diversity patterns of communities in this subtropical forest.