Dynamic of community structure in middle mountain evergreen and deciduous broad-leaved mixed forest in Cenwanglaoshan

Understanding the dynamics of community structure and species diversity in evergreen and deciduous broad-leaved mixed forests can provide a scientific foundation for effective forest management. To analyze data from two surveys conducted in 2015 and 2022, we employed α diversity index, β diversity index, principal coordinate analysis, and spatial point pattern analysis. Our study focused on three 1 hm2 communities at different elevations to investigate changes in species composition, species diversity and structure characteristics of diameter at breast height(DBH)class while exploring the causes of tree mortality. The results were as follows:(1)Tree mortality was greater in lower elevation communities than higher altitude ones. Tree death primarily affected small diameter trees and exhibited a non-random dead pattern independent of density dependence.(2)Overall α diversity of communities decreased slightly across all elevations over the course of seven years but not significantly so. The rate of change in α diversity index was relatively consistent among communities at different elevations. Although there were slight changes observed in the species composition within each community, these differences were minimal(P>0.99). A convergence trend was observed regarding species composition among communities at different elevations.(3)Average DBH and total basal area of all trees increased across communities at different elevations, with an inverted “J” shaped structure of DBH class indicating good self-renewal capacity and community stability maintenance ability. In summary, the changes observed in community structure of the evergreen and deciduous broad-leaved mixed forest in Cenwanglaoshan mountain are generally consistent across different elevations, thus demonstrating stable community structure with insignificant changes despite minor fluctuations occurring within dominant species population or rare species extinction impacting overall richness level.