Functional traits change but species diversity is not influenced by edge effects in an urban forest of Eastern China

Abstract

Forest edges have significant effects on plant species and trait compositions. However, most current studies on edge effects are based on natural forests, and studies on edge effects in urban forests are still limited. Here, we set up 50 survey plots in Wuchao Mountain National Forest Park, an urban forest of Hangzhou, China. We tested how species composition changed with distance from the forest edge. Specifically, we investigated dispersal-related traits for 86 species, and analyzed trait composition changes with distance from the forest edge. The NMDS analysis revealed a significant difference in species composition between forest edge and interior, but species richness and functional diversity remain unchanged. However, single traits showed higher divergence than expected. The percentage of fleshy-fruited species declined with distance from the edge, but plant abundance of mammal-dispersed and animal-dispersal seed mass was increased. The different trend in seed size of different dispersal mode and seed mass from edge to the interior within the community may be related to the loss of mammal-dispersed plant species at the forest edge. This suggests that edge effects have a high influence on functional traits in urban forests, but not on species diversity. Edges had significant effects on animal-dispersed species and trait composition of plant communities. Our study highlights the importance of maintaining forest integrity by protecting interior habitats in urban regions. We also recommend reducing the creation of new edges and increasing the buffer area for biodiversity conservation.