Dissertation Research: The Effects of Heterogeneity and Scale on Nutrient Dynamics in a Desert Stream

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9800912 Grimm The PIs propose to investigate the effects of spatial structure on nutrient dynamics at different scales in a stream-riparian ecosystem. Streams are heterogeneous ecosystems that transport nutrients from terrestrial uplands to lakes, reservoirs, groundwater aquifers and estuaries. The extent to which nutrients are retained, transported, or transformed depends on the path of water through ecosystem components, or patches, and residence time in each patch. Preliminary results show that, contrary to conventional wisdom, nutrient concentrations in stream water are highly variable in space. The PIs will describe the pattern of nutrient concentrations in stream surface water over a range of spatial scales, identify elements of ecosystem structure and associated processes that might explain these patterns at each scale, and develop a spatial structure-based simulation model to predict nutrient concentrations and nutrient retention as a function of spatial structure. The research will contribute to emerging ecological theory by examining how heterogeneity and the processes that cause it change with scale in a particular ecosystem. It will also aid in stream ecosystem management by increasing our understanding of nutrient dynamics in a desert stream catchment and by providing a simulation model for use in future ecosystem studies.