DISSERTATION RESEARCH: Secondary Production in Urban Stream Food Webs: From Pattern to Process

城市土地利用和未来城市扩张对自然生态系统构成严重威胁。城市地区依靠自然生态系统的外部支持来获取资源和处理废物。因此，城市系统中的河流受到流域内多重干扰的影响，并且在许多情况下充当城市废水排放的废物管道。此外，由于不透水表面（即道路，建筑物，停车场）的增加，流域水文的变化通过加深和拓宽溪流以适应新的流动模式，极大地影响了河道地貌。这些河流条件的物理和化学变化通常会导致河流栖息生物的生物多样性下降。然而，一个尚未解决的问题是，群落丰富度和多样性的减少如何影响城市河流群落提供的生态系统功能和服务。在本研究中，这个问题将通过在6条河流流域进行实验来解决，这些河流的土地利用从0到80%的城市覆盖范围变化，不仅确定河流内的生物多样性如何受到城市化的影响，而且确定这些生物多样性的损失在河流食物网内的能量流动和营养循环方面有什么后果，这两个过程对河流内的水质产生深远的影响。这些结果的传播将通过将通常观察到的河流生物多样性减少与河流生物提供的可测量的生态系统规模功能和服务联系起来，促进未来城市化河流的规划、管理和恢复。

Urban land use and future urban expansion pose a serious threat to natural ecosystems. Urban areas rely on outside support from natural ecosystems for resource acquisition and waste disposal. As a consequence, streams in urban systems are affected by multiple disturbances within the watershed, and, in many cases, serve as waste conduits for municipal wastewater discharge. In addition, changes in watershed hydrology due to increased impervious surfaces (i.e. roads, buildings, parking lots) drastically affect stream channel geomorphology by deepening and widening the stream to accommodate new flow patterns. These physical and chemical changes in stream conditions generally result in decreased biological diversity of stream dwelling organisms. An unaddressed question, however, is how reductions in community richness and diversity affect the ecosystem functions and services provided by urban stream communities. In this study, this question will be addressed by conducting experiments in six streams draining watersheds in which land use varies from 0 to 80% urban cover to determine not only how biological diversity within the stream is impacted by urbanization, but what consequences these losses in biological diversity have in terms of energy flow and nutrient cycling within stream food webs, two processes with profound consequences for in-stream water quality. Dissemination of these results will facilitate the future planning, management, and restoration of urbanized streams by linking commonly observed decreases in stream biological diversity with measureable ecosystem scale functions and services provided by the stream organisms.