Department of Ecology and Evolutionary Biology, University of California, 321 Steinhaus Hall, Irvine, California, 92697, USA.
Department of Marine and Ecological Sciences, Florida Gulf Coast University, 10501 FGCU Boulevard South, Fort Myers, Florida, 33965, USA.
Ecology. 2017 May;98(5):1434-1443. doi: 10.1002/ecy.1812.
Most studies evaluating the effects of biodiversity on ecosystem functioning are conducted at a single location, limiting our understanding of how diversity-function relationships may change when measured across different spatial scales. We conducted a species-removal experiment at three sites nested in each of three regions along the rocky intertidal coastline of the Gulf of Maine, USA, to evaluate the potential for scale-dependent effects of species loss on the biomass of intertidal seaweed assemblages. We randomly assigned 50 plots in the mid-intertidal zone at each site to one of five treatments (n = 10 plots each): an unmanipulated control, a polyculture plot that contained our three target seaweed species, and three monoculture plots. We manipulated diversity by removing all non-target species from monoculture and polyculture plots, then removing additional biomass from polyculture plots, proportionate to species' relative abundances, so that the average amount removed from monoculture and polyculture plots was equivalent at each site. At the largest spatial scale, all sites considered together, after accounting for region and site nested within region seaweed diversity had consistent, positive effects on seaweed cover. Diverse polyculture plots always had higher cover than was predicted by the average performance of the component seaweed species and usually had higher cover than even the best-performing component species. Diversity effects weakened and became less consistent at smaller spatial scales, so that at the scale of individual sites, diverse polycultures only performed better than the average of monocultures ~40% of the time. Hence, our results indicate that weak and/or inconsistent biodiversity effects at the level of individual sites may scale up to stronger, more consistent effects at larger spatial scales. Quantitative summaries of biodiversity experiments conducted at the scale of individual sites do not capture this spatial aspect of biodiversity effects and may therefore underestimate the functional consequences of biodiversity loss.
大多数评估生物多样性对生态系统功能影响的研究都是在单一地点进行的，这限制了我们对多样性-功能关系在跨不同空间尺度测量时如何变化的理解。我们在美国缅因湾的岩石潮间带的三个地区的三个地点进行了物种去除实验，以评估物种损失对潮间带海藻生物群落生物量的尺度相关影响的潜力。我们在每个地点的中潮带随机分配了 50 个斑块到五个处理中的一个（每个处理 10 个斑块）：未处理的对照、包含我们三个目标海藻物种的混养斑块和三个单种斑块。我们通过从单种和混养斑块中去除所有非目标物种来操纵多样性，然后从混养斑块中去除与物种相对丰度成比例的额外生物量，使得从单种和混养斑块中去除的平均量在每个地点相等。在最大的空间尺度上，考虑到所有站点，在考虑了区域和站点嵌套在区域内的情况下，海藻多样性对海藻覆盖具有一致的、积极的影响。多样的混养斑块的覆盖总是高于成分海藻物种平均表现所预测的水平，而且通常高于表现最好的成分物种的覆盖。多样性效应在较小的空间尺度上减弱且变得不那么一致，因此在单个站点的尺度上，多样的混养仅在约 40%的时间内表现优于单种的平均水平。因此，我们的结果表明，单个站点水平上的微弱和/或不一致的生物多样性效应可能会扩展到更大空间尺度上更强、更一致的效应。在单个站点规模上进行的生物多样性实验的定量总结没有捕捉到生物多样性效应的这种空间方面，因此可能低估了生物多样性丧失的功能后果。
