Patterns of Species Loss in Forest Understory Plant Communities

9974041沃勒许多地区的植物群落正以前所未有的速度失去物种。虽然造成这些损失的机制各不相同，而且往往难以确定，但似乎有一个总的趋势，决定了哪些物种最容易消失。稀有和局部物种通常面临更大的局部灭绝风险，物种丧失的模式往往导致大多数生境斑块含有常见和广泛分布的物种。栖息地破碎化、历史扰动制度的转变、外来物种的入侵以及白尾鹿种群数量增加的草食行为似乎都是导致各种栖息地损失的近因机制。本研究将调查威斯康辛州北部和密歇根州上半岛森林林下植物群落的组成和物种损失模式，以了解这些损失的性质、程度和机制。数据将从分布在该地区6个群落/土壤类型的120多个站点收集，以解决几个生态问题。为了测试物种损失的可预测性，将分析嵌套的物种组成。为了评估历史损失，当代物种存在数据将与约翰·t·柯蒂斯及其同事收集的这些森林的历史数据进行比较。将历史下降模式与生境斑块中当前筑巢模式进行比较，以评估当前筑巢模式对历史过程的反映程度。分层空间采样将使我们能够构建物种-面积曲线，以便在群落和土壤类型之间进行比较。这些结果将提高我们对自然群落动态、这些群落的历史变迁和物种丧失的当前机制的理解。

9974041WallerPlant communities in many areas are losing species at unprecedented rates. While the mechanisms responsible for these losses vary and are often difficult to identify, there appear to be general trends governing which species are most vulnerable to being lost. Rare and localized species are usually at greater risk of local extirpation, and patterns of species loss often result in most habitat patches containing common and widespread species. Habitat fragmentation, shifts in historic disturbance regimes, the invasion of exotic species, and herbivory by elevated populations of white-tailed deer all appear to be proximate mechanisms driving these losses in various habitats. This study will investigate patterns of community composition and species loss in understory plant communities in forests of northern Wisconsin and Michigan's upper peninsula as a vehicle to understand the nature, extent, and mechanisms of these losses. Data will be collected from 120+ sites distributed across six community/soil types in this region to address several ecological questions. To test the predictability of species loss, nested species compositions will be analyzed. To assess historic losses, contemporary species presence data will be compared to historical data collected by John T. Curtis and colleagues for these forests. Patterns of historical decline will be compared to current patterns of nestedness among habitat patches to assess how well current patterns of nestedness reflect historical processes. Hierarchical spatial sampling will allow us to construct species-area curves for comparisons across community and soil types. These results will improve our understanding of natural community dynamics, historical shifts in these communities, and current mechanisms of species loss.