Research
Ongoing Projects
Soil denitrification and climate change in northern hardwood forests in Hubbard Brook Experimental Forest, New Hampshire. Elevated N deposition across the Northeast US has altered nitrogen (N) cycling in recent decades; to fully understand the consequences of N deposition, we need to estimate denitrification rates more accurately. Using a new system to measure N2 and N2O production in intact soil cores, these measurements provide new data for an updated Northeast US nitrogen budget. To date, portions of this work have been published in: Journal of Geophysical Research-Biogeosciences, Oecologia, and Ecosystems.
Ecological homogenization of cities. Urban, suburban and exurban ecosystems are important and increasing in the US. Does urban land use change lead to ecological homogenization across cities, where neighborhoods in very different parts of the country have similar patterns of roads, residential lots, commercial areas and aquatic features. We hypothesize that this homogenization also involves ecological structure and functions relevant to ecosystem carbon and nitrogen dynamics, with continental scale implications. We hope that understanding urban homogenization will provide the basis for understanding the impacts of urban land use change from local to continental scales. To date, portions of this work have been published in Proceedings of the National Academy of Science, Ecosystems, and Frontiers in Ecology and the Environment.
Managing N cycling in agricultural settings.
Understanding how N can be managed in agricultural systems to minimize N runoff, groundwater nitrate leaching, and N2O emissions requires a clear understanding of soil denitrification that has been elusive to date. In a just-completed project in the Southern Willamette Valley in Oregon, we worked in collaboration with grass seed growers and fertilizer companies to experimentally test the effects of N fertilizer management on nitrate leaching to groundwater and N2O emissions.
An outreach video and factsheet summarize our findings for a public audience.
Recent Projects
Clean Water for All collaboration: With collaborators from across the U.K. and the Portland region, we are investigating multiple dimensions of how green infrastructure for stormwater management interfaces with biophysical and socio-economic dimensions of urban watersheds. The specific focus of my lab within this broader project was to examine the influence of stormwater pipes and green infrastructure on sediment biogeochemistry in a rural-to-urban river network (Johnson Creek, Portland, OR). Portions of this work have been published in the Journal of Flood Risk Management.
Wetland restoration and ecosystem services. We addressed the question of whether re-flooding former agricultural lands for wetland restoration in coastal North Carolina would lead to increased greenhouse gas emissions from these sites. Emissions of nitrous oxide (N2O), one of the most potent biogenic greenhouse gases, were expected to increase through higher denitrification in wetter, N-rich soils. We found that N2O fluxes from the restored wetland did not exceed fluxes from nearby agricultural fields and forested wetlands, and they measured water quality improvements downstream of the restored wetland. To date, portions of this work have been published in Ecological Applications, Ecosystems, Journal of Geophysical Research-Biogeosciences, and Soil Biology and Biochemistry.
