multidimensional beta-diversity across local and regional scales in a Chinese subtropical forest: the role of forest structure

Beta-diversity, or the spatio-temporal variation in community composition, can be partitioned into turnover and nestedness components in a multidimensional framework. Forest structure, including comprehensive characteristics of vertical and horizontal complexity, strongly affects species composition and its spatial variation. However, the effects of forest structure on beta-diversity patterns in multidimensional and multiple-scale contexts are poorly understood. Here, we assessed beta-diversity at local (a 20-ha forest dynamics plot) and regional (a plot network composed of 19 1-ha plots) scales in a Chinese subtropical evergreen broad-leaved forest. We then evaluated the relative importance of forest structure, topography, and spatial structure on beta-diversity and its turnover and nestedness components in taxonomic, functional, and phylogenetic dimensions at local and regional scales. We derived forest structural parameters from both unmanned aerial vehicle light detection and ranging (UAV LiDAR) data and plot inventory data. Turnover component dominated total beta-diversity for all dimensions at the two scales. With the exception of some components (taxonomic and functional turnover at the local scale; functional nestedness at the regional scale), environmental factors (i.e., topography and forest structure) contributed more than pure spatial variation. Explanations of forest structure for beta-diversity and its component patterns at the local scale were higher than those at the regional scale. The joint effects of spatial structure and forest structure influenced component patterns in all dimensions (except for functional turnover) to some extent at the local scale, while pure forest structure influenced taxonomic and phylogenetic nestedness patterns to some extent at the regional scale. Our results highlight the importance and scale dependence of forest structure in shaping multidimensional beta-diversity and its component patterns. Clearly, further studies need to link forest structure directly to ecological processes (e.g., asymmetric light competition and disturbance dynamics) and explore its roles in biodiversity maintenance.

β多样性（beta-diversity）即群落组成的时空变异，可在多维框架下拆解为物种更替（turnover）与嵌套性（nestedness）两个组分。森林结构涵盖垂直与水平复杂性的综合特征，对物种组成及其空间变异具有显著调控作用，但当前学界对森林结构在多维、多尺度背景下对β多样性格局的影响机制仍知之甚少。本研究在中国亚热带常绿阔叶林内，分别于局部尺度（20公顷森林动态监测样地）与区域尺度（由19个1公顷样地组成的样地网络）开展β多样性评估，进而分析了森林结构、地形与空间结构在局部与区域尺度下，对分类学、功能学及系统发育维度的β多样性及其物种更替、嵌套性组分的相对重要性。研究基于无人机激光雷达（UAV LiDAR）数据与样地调查数据提取森林结构参数。结果显示，在两个尺度下的所有维度中，物种更替组分均主导了总β多样性。除局部尺度的分类学与功能学物种更替、区域尺度的功能学嵌套性等少数组分外，环境因子（即地形与森林结构）的解释力均高于纯空间变异。森林结构对β多样性及其组分格局的解释力在局部尺度高于区域尺度。在局部尺度，空间结构与森林结构的联合效应对除功能学物种更替外的所有维度的组分格局均存在一定程度的影响；而在区域尺度，纯森林结构仅对分类学与系统发育嵌套性格局存在一定程度的影响。本研究结果凸显了森林结构在调控多维β多样性及其组分格局中的重要性及其尺度依赖性。显然，未来研究需将森林结构与生态过程（如非对称光竞争与干扰动态）直接关联，并探讨其在生物多样性维持中的作用。