Program in Ecology, Evolution, and Conservation Biology, University of Illinois, 505 S. Goodwin Ave, Urbana, IL 61801, USA.
Proc Biol Sci. 2012 Dec 19;280(1753):20122532. doi: 10.1098/rspb.2012.2532. Print 2013 Feb 22.
Both habitat filtering and dispersal limitation influence the compositional structure of forest communities, but previous studies examining the relative contributions of these processes with variation partitioning have primarily used topography to represent the influence of the environment. Here, we bring together data on both topography and soil resource variation within eight large (24-50 ha) tropical forest plots, and use variation partitioning to decompose community compositional variation into fractions explained by spatial, soil resource and topographic variables. Both soil resources and topography account for significant and approximately equal variation in tree community composition (9-34% and 5-29%, respectively), and all environmental variables together explain 13-39% of compositional variation within a plot. A large fraction of variation (19-37%) was spatially structured, yet unexplained by the environment, suggesting an important role for dispersal processes and unmeasured environmental variables. For the majority of sites, adding soil resource variables to topography nearly doubled the inferred role of habitat filtering, accounting for variation in compositional structure that would previously have been attributable to dispersal. Our results, illustrated using a new graphical depiction of community structure within these plots, demonstrate the importance of small-scale environmental variation in shaping local community structure in diverse tropical forests around the globe.
生境过滤和扩散限制均会影响森林群落的组成结构，但此前利用地形来代表环境影响，通过划分变异来检验这些过程相对贡献的研究主要集中在地形上。在这里，我们整合了 8 个大型（24-50 公顷）热带森林样地内的地形和土壤资源变化数据，并利用划分变异来将群落组成变化分解为由空间、土壤资源和地形变量解释的部分。土壤资源和地形都解释了树木群落组成的显著且大致相等的变异（分别为 9-34%和 5-29%），所有环境变量共同解释了一个样地内组成变化的 13-39%。很大一部分变异（19-37%）是空间结构的，但无法用环境来解释，这表明扩散过程和未测量的环境变量发挥了重要作用。对于大多数样地来说，将土壤资源变量添加到地形中几乎使生境过滤的推断作用增加了一倍，这解释了以前归因于扩散的组成结构变化。我们的结果通过在这些样地内用一种新的群落结构图形表示法来说明，表明了在全球不同热带森林中，小尺度环境变化在塑造局部群落结构方面的重要性。
