Data from: Habitat patterns in tropical rain forests: a comparison of 105 plots in northwest Borneo

Understanding the maintenance of high tropical tree species diversity
requires disentangling the effects of habitat vs. geographic distance.
Using floristic, topographic, and soil nutrient data from 105 0.6-ha plots
in mixed dipterocarp forest throughout Sarawak, Malaysian Borneo, we
explore the degree to which floristic patterns are habitat-driven from
local to landscape scales. We assess how the floristic influence of
geographic distance vs. abiotic factors varies from local to regional
scales. We employ several multivariate analytical techniques and perform a
hierarchical clustering of the research plots using the Steinhaus index of
floristic dissimilarity, as well as Mantel analyses on matrices of
floristic, habitat, and geographic distance. These analyses indicate that
floristic variation is more strongly correlated with habitat than with
geographic distance on the regional scale. On the local-landscape to
community scale, we find evidence of a resource threshold above which
habitat effects weaken; that is, below the resource threshold floristic
similarity between sites is dominated by habitat effects, while above the
threshold floristic similarity between sites is dominated by
geographic-distance effects. We also find evidence that topography and
soil nutrients correlate in part independently with floristics. These
results, together with previous studies in the Neotropics, emphasize that
tree species distribution and community composition are variously
influenced by the interplay of both habitat and dispersal-driven effects.

阐明热带树木物种高多样性的维持机制，需要厘清生境与地理距离的各自效应。本研究依托马来西亚婆罗洲砂拉越地区全域混合龙脑香林内105块面积为0.6公顷的样地所获取的植物区系、地形及土壤养分数据，探究从局域到景观尺度下，植物区系格局在多大程度上由生境驱动。本研究同时评估，从局域到区域尺度，地理距离与非生物因子对植物区系的影响强度如何变化。本研究采用多种多元分析方法，基于植物区系相异性的斯坦豪斯指数（Steinhaus index）对研究样地进行层级聚类，并针对植物区系、生境及地理距离的距离矩阵开展曼特尔分析（Mantel analyses）。上述分析结果显示，在区域尺度上，植物区系变异与生境的相关性显著强于其与地理距离的相关性。在局域-景观至群落尺度上，本研究发现存在一处资源阈值：当生境效应在阈值之上时会减弱——具体而言，低于该阈值时，样地间的植物区系相似性主要由生境效应主导；而高于该阈值时，样地间的植物区系相似性则由地理距离效应主导。本研究同时证实，地形与土壤养分可在部分维度上独立于彼此与植物区系特征形成关联。本研究结果结合此前新热带区的相关研究，共同表明：树木物种的分布与群落组成，会受到生境效应与扩散驱动效应的共同调控，且二者的相对影响存在差异。