Diversity Of Subtropical Broad-leaved Evergreen Forest Communities At Different Scales And In Different Dimensions

The maintenance mechanisms of biodiversity are one of the central for ecological research.Forest stand structure can characterize the light availability and heterogeneity of forest communities.However,few studies have applied forest stand structure to explain the variation of biodiversity maintenance mechanisms.In this study,for the same forest ecosystem,all tree species with DBH≥10 cm in the 20-ha subtropical mid-mountain moist evergreen broad-leaved forest dynamics plot in Ailao Mountains(local scale,less than 1 square kilometer)and 19 1-ha forest dynamics plots established among grids of 1 km~2in Ailao mountains(regional scale)were studied.The relative importance of environmental filter in driving variation in community species composition was explored at the local and regional scales,and the relative role of forest stand structure in driving variation in community species composition was clarified in particular by canonical redundancy analysis and variance partitioning.The role of forest stand structure in the maintenance of biodiversity has been comprehensively analyzed from a multi-scale and multi-dimensional perspective by including stand structure in the study of the driving effects ofα-diversity andβ-diversity in different dimensions(taxonomic,functional traits and phylogenetic diversity),with the following main findings:(1)The inclusion of forest stand structure as an explanatory variable significantly increased the explanatory rate of variation in species composition at both local and regional scales,and in terms of the relative contribution of individual explanatory variables,the first principal component of forest stand structure,which primarily reflects light availability,had the higher explanatory rate at both local and regional scales.(2)The analysis of environmental factors and forest stand structure correlations on different dimensions ofαdiversity revealed that at the local scale,forest stand structure was significantly correlated with taxonomic and functionalαdiversity,but not with phylogeneticαdiversity;the role of environmental factors on all threeαdiversities was not significant.(3)Comparing the different dimensions ofβdiversity at both local and regional scales,both showed the highest taxonomicβdiversity,followed by functionalβdiversity,and the lowest phylogeneticβdiversity,with no significant scale differences.(4)The relative importance of environmental filtering and dispersal limitation was explored by variance partitioning,and it was found that the joint effect of environmental and spatial structure of the environment,had a higher relative contribution to explainingβdiversity patterns at local and regional scales and all the three different dimensions ofβdiversity.i.e.,environmental filtering had a higher effect onβdiversity compared to dispersal limitation.This study confirms that forest stand structure,which characterizes the light environment,is an important driver of variation in community species composition for subtropical broad-leaved evergreen forests and that forest stand structure has a strong role in shapingαdiversity at different scales and dimensions,and thatβdiversity patterns at different scales and dimensions are mainly driven by environmental filtering.The inclusion of forest stand structure analysis helps to deepen the understanding of the role of environmental filtering in driving biodiversity maintenance mechanisms and compensates for the traditional inadequate consideration of environmental factors,and future studies should further explore the intrinsic mechanisms of forest stand structure on biodiversity patterns in subtropical broad-leaved evergreen forests.