Resource heterogeneity and the environmental basis of productivity in flowing waters

溪流食物网内使用的能量很大一部分来自陆地植物材料和其他外部来源，即，生态系统补贴。 有许多来源的变化，在食物的质量，数量和可用性，这些材料的消费生物在流社区。 本提案将处理这种资源异质性的原因和后果。 变化的原因包括特定资源（如落叶、鲑鱼尸体等）的可用性时间。以及水文、地貌、光输入和温度等影响其可用性的物理驱动因素的变化。 许多这些有形驱动因素影响到这些资源的保留，在气候变化情景下，驱动因素预计也会在时间和规模上发生变化。资源本身是异质的，代表了有机碳和各种微生物（真菌，细菌和藻类）的复杂分类。这些不同的微生物如何相互作用以及与碳源的相互作用将影响动物食物的质量和数量，但其后果尚不清楚。 这一系列的实验将测试假设的性质，在这些食物的变化的基础上的小溪流的食物网的生产力和水生生物群落的后果。 水生群落中的许多物种被认为是叶碎屑的专性消费者，但在一些溪流中，消费者的替代资源包括鲑鱼尸体和生物膜，这些在时间和空间上都是高度不规则的。 因此，其他资源的贡献是短暂的，零散的，或两者兼而有之，但由于其高质量，可能具有潜在的重要性。 我们的实验将操纵资源的质量和数量，光输入，物理结构，甚至水文（使用短距离改道），以测试对消费无脊椎动物及其社区的生长和生存的影响。预计气候变化、陆地植被变化和空中运输导致的营养物质浓度增加将导致食物资源的变化，我们的工作将测试对预期影响的预测。

A very large proportion of the energy used within stream food webs is derived from terrestrial plant material and other external sources, i.e., ecosystem subsidies. There are many sources of variation in the food quality, quantity, and availability of these materials for consumer organisms within the stream community. This proposal will address the causes and consequences of such resource heterogeneity. The causes of variation include timing of availability of particular resources (e.g. leaf litter, salmon carcasses, etc.) and changes in the physical drivers of their availability, such as hydrology, geomorphology, light inputs and temperature. Many of these physical drivers affect retention of these resources, and drivers are also expected to change in timing and magnitude under climate change scenarios. The resources themselves are heterogeneous and represent a complex assortment of organic carbon and various micro-organisms (fungi, bacteria, and algae). How these various micro-organisms interact with each other and with carbon sources will influence food quality and quantity for animals but the consequences are not well known. This series of experiments will test hypotheses about the nature of the variation in these food materials as the basis of productivity of food webs of small streams and the consequences for the aquatic community. Many species within aquatic communities are considered to be obligate consumers of leaf detritus, but alternate resources for consumers in some streams include salmon carcasses and biofilms, and these are highly patchy in time and space. Hence, the contributions of other resources are short-lived, patchy, or both, but may be potentially important because of their high quality. Our experiments will manipulate the quality and quantity of resources, light inputs, physical structure, and even hydrology (using short-distance diversions) to test impacts on growth and survival of consumer invertebrates and their community. Shifts in food resources are expected as a consequence of variation in climate, changes in terrestrial vegetation, and enhanced nutrient concentrations from airborne transport, and our work will test predictions of expected impacts.