Tree niche characteristics primarily regulate species, phylogenetic and functional diversity of tree communities...

Ecological niche represents the range of available resources or adaptable habitat environments and is highly relevant to species distribution, community composition, ecosystem functioning, and biodiversity conservation strategies. Despite the importance of niche's concept and application in ecology and environmental science, there is a lack of research on the mechanisms by which generalists with broad niches and specialists with narrow niches control tree diversity. Furthermore, there is need for studies that quantify the niches of species using various environmental variables for estimating different facets of diversity on a wide spatial scale. We used vegetation data from Korean national forest inventory for a total of 3262 plots of natural forests, including 715, 1607 and 940 plots of conifer, broadleaved, and 940 mixed stands, respectively. Using the averaging approach of multimodel inference, assessing the importance of each variable for impacting three facets of tree diversity such as species, phylogenetic and functional diversity, and piecewise structural equation modeling was used for evaluate the direct and indirect control mechanisms of abiotic and tree niche characteristics on three facets of tree diversity. The results showed that in all forest types, abiotic drivers affect taxonomic, phylogenetic and functional diversity of tree communities through similar contributions and pathways. Niche characteristics had a greater impact on three diversity facets than abiotic drivers. Moreover, among the three diversity facets niche characteristics had a greater impact on species diversity. Our results provide insights into the importance and potential utility of niche characteristics in estimating different facets of biodiversity indices. Based on the results of this study, the sustainable management strategies of forest ecosystems including enhancement of biodiversity and restoration to make health ecosystem need to be organized around niche types (e.g., generalists, specialists) and breadth of species according to environmental conditions and forest types.