Patterns of diversity and community assembly change across local to regional scales: An evidence of deterministic assembly processes along resource availability gradient at temperate forest

Diversity and its maintaining mechanism (community assembly) shift along resource availability gradients at local and regional levels. It is necessary to identify key natural factors shaping community assembly or diversity patterns, so that understanding the patterns of diversity and assembly along these factors across local to regional scales. In this study, we investigated the six local sites of plant community in Qinling Mountains region. Based on the relative importance of environmental factors in shaping the phylogenetic diversity, a complex resource availability gradient was established to assess taxonomic and phylogenetic diversity and assembly patterns along it at local or regional scale separately. Phylogenetic analyses and the biodiversity index were estimated along environmental gradients as well, to assess the difference between change tendencies along natural environmental and resource availability gradients. We found that 1) elevation was the most important regional-scale environmental predictor of phylogeny of community; 2) taxonomic and phylogenetic diversity studies showed similar patterns along both resource and elevational gradients at regional scale, and that diversity at local scale may differ regardless of gradients; 3) at the regional level, phylogenetic structures revealed convergent tendencies along the elevational gradient across different species pools. Phylogenetic assembly patterns along the elevation gradient at the local scale differed from the patterns at the regional scale, with consistent clustering tending to overspread along the resource availability gradient. In conclusion, resource availability shaped community assembly at the regional level. Local patterns of diversity influenced regional patterns differently because of variation in the colonization history or assembly process. Owing to varying assembly patterns along simple environmental gradients, it is vital to establish a complex resource availability gradient to dissect the real assembly mechanism or biodiversity patterns operating in local to regional-scale processes. These findings may provide valuable reference about forest restoration and management.