Biodiversity patterns are shaped by the combination of dispersal, environment, and stochasticity, but how the influence of these drivers changes in fragmented habitats remains poorly understood. We examined patterns and relationships among total (γ) and site‐level (α) diversity, and site‐to‐site variation in composition (β‐diversity) of tree communities in structurally contiguous and fragmented tropical rainforests within a human‐modified landscape in India's Western Ghats. First, for the entire landscape, we assessed the extent to which habitat type (fragment or contiguous forest), space and environment explained variation in α‐diversity and composition. Next, within fragments and contiguous forest, we assessed the relative contribution of spatial proximity, environmental similarity, and their joint effects in explaining β‐diversity. We repeated these assessments with β‐diversity values corrected for the confounding effects of α‐ and γ‐diversity using null models (β‐deviation). Lower γ‐diversity of fragments resulted from both lower α‐ and β‐diversity compared to contiguous forests. However, β‐deviation did not differ between contiguous forests and fragments. Fragmented and contiguous forest clearly diverged in floristic composition, which was attributable to β‐diversity being driven by differences in elevation and MAP. Within fragmented forest, neither space nor environment explained β‐diversity, but β‐deviation increased with greater elevational differences. In contiguous forests by comparison, environment alone (mainly elevation) explained the most variation in β‐diversity and β‐deviation of both species' occurrences and abundances. Spatial gradients in environmental conditions played a larger role than dispersal limitation in shaping diversity and composition of tree communities across forest fragments. Thus, location of remnant patches at different elevations was a key factor underlying site‐to‐site variability in species abundances across fragments. Understanding the environmental characteristics of remnant forests in human‐modified landscapes, combined with knowledge of species–environment relationships across different functional groups, would therefore be important considerations for management and restoration planning in human‐modified landscapes.

中文翻译：

---

在人类改造的景观中，环境影响着零散森林中树木多样性的空间组织

生物多样性的模式是由分散性，环境和随机性共同决定的，但这些驱动因素的影响如何在零散的生境中变化仍然知之甚少。我们研究了人类改造景观内结构连续和零散的热带雨林中树木群落的总（γ）和位点水平（α）多样性以及位点间组成变异（β多样性）之间的模式和关系。印度的西高止山脉。首先，对于整个景观，我们评估了栖息地类型（片段或连续森林），空间和环境在多大程度上解释了α多样性和组成的变化。接下来，在碎片和连续森林中，我们评估了空间邻近性，环境相似性及其在解释β多样性方面的共同作用的相对贡献。我们重复了这些评估，并使用零模型（β偏差）校正了针对α和γ多样性的混杂效应的β多样性值。与连续森林相比，较低的α和β多样性导致碎片的较低的γ多样性。但是，连续森林和碎片之间的β偏差没有差异。零散而连续的森林在植物组成上明显不同，这是由于海拔和MAP的差异驱动了β多样性。在零散的森林中，空间和环境都不能解释β多样性，但是β偏差随着海拔差异的增加而增加。相比之下，在连续森林中，仅环境（主要是海拔）解释了两种物种的发生和丰度的β多样性和β偏差的最大变化。在塑造整个森林碎片中树木群落的多样性和组成方面，环境条件下的空间梯度起着比扩散限制更大的作用。因此，残留斑块在不同海拔的位置是跨片段物种丰度的点对点变异性的关键因素。因此，了解人类修饰景观中的残留森林的环境特征，并了解不同功能组之间的物种与环境之间的关系，将成为人类修饰景观的管理和恢复规划的重要考虑因素。残留斑块在不同海拔的位置是造成整个物种跨物种多样性的点对点变异性的关键因素。因此，了解人类修饰景观中的残留森林的环境特征，并了解不同功能组之间的物种与环境之间的关系，将成为人类修饰景观的管理和恢复规划的重要考虑因素。残留斑块在不同海拔的位置是造成整个物种跨物种多样性的点对点变异性的关键因素。因此，了解人类修饰景观中的残留森林的环境特征，并了解不同功能组之间的物种与环境之间的关系，将成为人类修饰景观的管理和恢复规划的重要考虑因素。