Data from: Fire may mediate effects of landscape connectivity on plant community richness in prairie remnants

Following the predictions of island biogeography and metapopulation theory, efforts to understand and maintain plant communities have focused on spatial attributes such as patch size and connectivity. However, despite a large body of literature, the effects of these spatial attributes remain uncertain, and accumulating evidence suggests that they may interact with local patch characteristics. Here, we assess the role of spatial attributes (patch size and connectivity at two time periods) and of patch quality (indicated by number of years since last fire, as this is a fire-dependent system) in determining plant species richness at 63 remnant prairie sites in Wisconsin, USA. Our results demonstrate significant main effects of patch size, with larger patches being richer than small patches, and of fire, with recent-fire sites being richer than fire-excluded sites. We also report a novel interaction between number of years since fire and patch connectivity. Historical (1950) connectivity was negatively related to species richness at recent-fire sites, but positively related to species richness at fire-excluded sites, while current (2000) connectivity and species richness were positively correlated at recent-fire sites, but unrelated at fire-excluded sites. Our findings indicate that measures of patch quality such as time since last fire can alter the association between spatial attributes such as patch size or connectivity and species richness.

遵循岛屿生物地理学（island biogeography）与集合种群理论（metapopulation theory）的预测，学界在解析与维持植物群落的研究中，长期聚焦于斑块面积、连通性等空间属性。然而，尽管已有大量相关研究文献，这类空间属性的生态效应仍未明确，且越来越多的证据表明，它们可能与斑块局部特征存在交互作用。本研究以美国威斯康星州的63处残存草原样地为研究对象，评估两类因子对植物物种丰富度的调控作用：一是空间属性（两个时间节点下的斑块面积与连通性），二是斑块质量（以末次火后年限表征，本研究区域属于火依赖型生态系统）。研究结果显示，斑块面积与火烧历史均存在显著的主效应：斑块面积越大，物种丰富度越高；经历近期火烧的样地，物种丰富度显著高于长期排除火烧的样地。本研究还发现了末次火后年限与斑块连通性之间的全新交互效应：历史连通性（1950年）的效应存在分化，在经历近期火烧的样地中，其与物种丰富度呈负相关，但在长期排除火烧的样地中则呈正相关；而当前连通性（2000年）仅在近期火烧样地中与物种丰富度呈显著正相关，在无火烧样地中则无显著关联。本研究结果表明，斑块质量的表征指标（如末次火后年限），能够改变斑块面积、连通性等空间属性与植物物种丰富度之间的关联模式。