I model soil carbon (C) and nitrogen (N) dynamics, especially in response to human perturbation of biogeochemical cycles. Soils contain the largest terrestrial reservoir of organic C and N. While the availability of this energy and nutrient reservoir to freshwater and ultimately marine ecosystems largely depends on the soil state factors: parent material, climate, biota, geomorphology, and time, human perturbation of biogeochemical cycles may shift the dynamic steady state of soil organic matter (SOM) pools. My research focuses on two ecosystems, northeastern temperate forests and North American grain agroecosystems. Currently, I am developing models of soil organic matter dynamics of northeastern temperate forests, with emphasis on catchment-scale C and N storage and export in response to increased atmospheric CO2 and N deposition. Our central philosophy is to model SOM age fractions that are measurable and to explicitly represent microbial processing of SOM. Our model considers system inputs from leaf, root, and coarse woody debris litter, as well as N deposition. Element export occurs as CO2 or N gas flux, or as inorganic N or DOM loss to freshwater ecosystems. The model system represents forest floor, organic, A, and B soil horizons; SOC, SON, microbial, and inorganic N pools are tracked in each horizon.
My work in agroecosystems focuses on how agricultural land management decisions alter nitrogen export from agricultural watersheds in the Mississippi River Basin and Chesapeake Watershed. Our work emphasizes ecological approaches to agroecosystem management as an alternative to conventional practices.