DISSERTATION RESEARCH: Putting the Relationship Between Species Diversity and Ecosystem Functioning into Context.

随着全球物种灭绝速度的迅速加快，科学家们就是否需要高度物种多样性来维持对生态系统功能至关重要的生态过程(如初级生产力、分解和养分循环等过程)展开了激烈的辩论。有限的证据表明，某些类型的生态系统可能比其他类型需要更多的物种。例如，最近的实验工作导致了这样的假设，即以周期性干扰为特征的生态系统中物种多样性的减少会导致生态过程的更大变化，而不是以干扰为特征的生态系统中物种多样性的减少。目前的研究将通过将物种多样性与洪水状况不同的河流生态系统中3个生态过程的速率(=干扰度量)相关联来验证这一假设。利用美国地质调查局的记录，来自美国东部的200条随机选择的河流将根据它们的频率和洪水泛滥的可预测性进行排名。将对最具洪水特征的25条溪流和最不具有洪水特征的25条溪流进行采样，以确定三个生态过程(初级生产力、树叶分解和水中悬浮颗粒的去除)的速率，以及影响这些过程的物种多样性(初级生产者、无脊椎动物和无脊椎动物滤食性动物)。为了验证这一假设，(1)藻类多样性与初级生产力之间的关系，(2)无脊椎动物有害生物多样性与树叶分解之间的关系，以及(3)无脊椎动物滤食多样性与悬浮颗粒物滞留之间的关系，将在洪水特征最多和最少的溪流中进行统计比较。结果将有助于确定物种多样性对于保护自然或人为干扰的生态系统中的生物过程是更重要还是更不重要。这项研究还将提供亟需的基本信息，说明可能调节物种多样性对生态系统水平过程的贡献的因素。

With the rate of global species extinction rapidly increasing, there is an intensifying debate among scientists as to whether or not a high diversity of species is required to maintain ecological processes that are important for the functioning of ecosystems (processes like primary productivity, decomposition, and the cycling of nutrients). Limited evidence suggests that the certain types of ecosystems may require more species than others. For example, recent experimental work has led to the hypothesis that decreasing species diversity in ecosystems characterized by periodic disturbances leads to greater changes in ecological processes than decreasing species diversity in ecosystems less characterized by disturbance. The current research will test this hypothesis by relating species diversity to the rates of 3 ecological processes in stream ecosystems that differ in flooding regime (=disturbance metric). Using records from the US Geological Survey, 200 randomly selected streams from the eastern United States will be ranked according to their frequency and predictability of bank-full flooding. The 25 streams most characterized by flooding and 25 streams least characterized by flooding will be sampled to determine the rates of three ecological processes (primary productivity, leaf decomposition, and removal of suspended particles from the water), and the diversity of species that influence these processes (primary producers, invertebrate detritivores, and invertebrate filter feeders). To test the hypothesis, the relationships between (1) algal diversity and primary productivity, (2) invertebrate detritivore diversity and leaf decomposition, and (3) invertebrate filter-feeder diversity and retention of suspended particulate matter, will be statistically compared between streams most and least characterized by flooding. The results will help determine whether species diversity is more or less important for conserving biological processes in ecosystems that are naturally or anthropogenically disturbed. This study will also provide much needed, basic information about the factors that potentially regulate the contribution of species diversity to ecosystem-level processes.