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The release of inorganic nitrogen from intensive agricultural practicces and urbanization has resulted in significant alterations of the aquatic nitrogen cycle in riparian ecosystems. Yet impacts of stream nitrogen inputs on the terrestrial nitrogen, carbon and water cycles, as well as riparian plant community structure are unclear. To address these issues, we constructed a dual-plot artificial stream riparian system within a plantation of a dioecious riparian tree species; box elder (Acer negundo) (Figure 1). The dual-plot design allows us to vary concentrations of stream inorganic nitrogen between plots, while controlling for ecohydrologic and geohydrologic variability. The system is currently being used to investigate elevated inorganic stream impacts on water use patterns, above ground productivity, and leaf chemistry of streamside male and female box elder trees. Previous work shows that female box elder trees along stream margins out perform co-occurring male box elder trees. We are first testing whether elevated stream nitrogen has a disparate impact on the physiology and resource uptake of male and female box elder trees. And second, whether elevated stream nitrogen has significant consequences on plant community structure and ecohydrologic processes of riparian ecosystems.

Figure 1 - Reconstructed riparian ecosystem at the Department of Biology Growth Site on the campus of the University of Utah.