Multi-Scale Coupled Natural-Human System Dynamics of Nitrogen in Residential Landscapes

Runoff from urban and suburban landscapes has long been known to have a significant effect upon the water quality of streams that receive this discharge. A particular concern in this area is the export of excess nitrate from the use of fertilizers on lawns, which can promote algal or microbial growth in receiving waters. Recent research has indicated that such nitrate export is less than expected, but the reasons for this are unclear. This project will investigate both the natural processes that may regulate the retention and discharge of nitrogen from lawns, as well as the sociological forces that influence the decisions of homeowners concerning the level of lawn management. The results will be incorporated into a model that will identify the locations and episodes of high nitrate in runoff in order to determine how human decisions and natural processes work together to control these concentrations. The conclusions will be applicable to a wide variety of urban and suburban locations across the country and the project will have direct benefit to the management of the environmental health of Chesapeake Bay.

This project models multi-scale, coupled-system dynamics of nitrogen in residential landscapes to determine how biogeochemical, hydrologic, and human behavioral processes interact to control nitrogen exports from residential ecosystems and landscapes. These models will coordinate information from household surveys, existing data, and geographic information system analyses to evaluate interconnected spatial patterns of lawn management and hydrologic sensitivity. The overarching hypothesis is that large-scale social and institutional influences often induce homeowner lawn-care practices contrary to homeowner preferences, but that significant changes in behavior can be motivated via systematic incentives. Field studies on plots varying in land use history (forest versus agriculture), site management (fertilizer input) and age will be established to test hypotheses about the limits of nitrogen sequestration in lawn soil profiles. Geographic, biogeochemical, and social-science data will be analyzed using ecohydrological models to produce spatial analyses of potential hotspots of lawn fertilizer export at the watershed scale. The effect of alternative policies and homeowner practices on land management and nitrogen exports can then be evaluated rigorously.