CRB: Plant Communities on Patchy Serpertine Outcrops: Spatial Structure and Ecological Interactions

加利福尼亚州北部的9424137个哈里森蛇形露头是具有丰富本土植物的生态岛。这项研究考察了蛇纹岩土壤上植物群落结构的两个相关方面，与保护生物学直接和普遍相关。第一个问题是如何在蛇纹岩土壤和非蛇纹岩土壤上构建植物群落多样性的空间结构，以及这种空间结构如何受到蛇纹岩的斑块和其他属性的影响。在保持采样区大小和间距不变的情况下，将比较蛇形和非蛇形基质之间以及斑状和连续蛇形基质之间物种组成的空间周转。这将是首次严格测试斑块相对于距离在产生群落多样性的空间组成部分方面所起的作用。为了评估地方性和非侵袭性的作用，将分别排除地方性和外来物种，重复上述分析。每对地点之间的物种周转将根据每种生境类型内的距离和环境差异进行回归，以进一步量化空间周转及其原因。第二个问题涉及多样性模式的生物原因。实验将检验关键的生物相互作用的速度如何随着蛇纹石斑块的大小和隔离而变化。授粉和种子捕食将在两个蛇形特有植物物种中进行测量，沿着自然和实验的斑块隔离梯度。这项研究将阐明如何最好地保护加州蛇纹土上的植物群落，以及更普遍的问题，即几个空间尺度上的斑块如何影响生态群落的结构和功能。随着人类活动逐渐增加自然系统的碎片化速度和程度，这项研究变得更加重要。

9424137 Harrison Serpentine outcrops in Northern California are ecological islands with a rich native flora. This study examines two related aspects of plant community structure on serpentine soils, with both immediate and general relevance for conservation biology. The first question is how plant community diversity is spatially structured on serpentine versus non-serpentine soils, and how this spatial structure is affected by patchiness and other attributes of serpentine. Spatial turnover in species composition will be compared between serpentine and non-serpentine substrates, and between patchy and continuous serpentine, while holding the size and spacing of sampling areas constant. This well be the first rigorous test of the role of patchiness versus distance alone in producing the spatial component of community diversity. To assess the roles of endemism and lack of invasion, the above analyses will be repeated excluding endemics and alien species, respectively. Species turnover between pairs of sites will be regressed on distance and environmental dissimilarity within each habitat type to further quantify spatial turnover and its causes. The second question concerns biotic causes of patterns of diversity. Experiments will examine how the rates of key biotic interactions vary with the size and isolation of serpentine patches. Pollination and seed predation will be measured in two serpentine endemic plant species, along both natural and experimental gradients of patch isolation. This study will illuminate both how best to conserve plant communities on serpentine soils in California, and the more general issue of how patchiness at several spatial scales affects the structure and function of ecological communities. This research becomes even more important as human activities gradually increase the rate and degree of fragmentation of natural systems.