9615358 Grimm The primary objective of this LTREB project is to understand the link between climate variability and the structure and functioning of running water ecosystems in arid lands. Year to year variability in precipitation is great in arid regions and precipitation regime determines the relative influence of drying and flash floods on desert streams and rivers. In addition to water, nutrients derived from desert uplands control rates of biological productivity in streams and adjacent riparian zones. Flux of nutrients from upland to streams is higher after several years of drought than after long wet periods. The specific objective of this research is to determine the influence of alternating wet and dry years on water and nitrogen transport in the landscape and its eventual utilization in streams and riparian wetlands. Methods include long-term monitoring of quantity and nutrient content of precipitation, overland flow at several upland points, and streamwater in channels with permanent flow. Stream ecosystem response will be measured in terms of several algal and macroinvertebrate community parameters, rate of reestablishment of communities after flood and drought, and patterns of nutrient cycling in the aquatic sector. Research will be performed in the Sycamore Creek catchment ecosystem of central Arizona. Arid lands are extensive nationally and globally and water is the critical resource therein, yet little is known about how upland deserts and rare surface water ecosystems are linked. The nature of this linkage is central to an understanding of factors determining water quality in arid lands. Changing climate, anthropogenic or otherwise, is likely to alter not only precipitation regime, but also land use and natural vegetation patterns. This long-term research project will enhance our knowledge of how entire catchment ecosystems respond to changing climate and the consequences of this response for both natural habitat and water quality.
