Baltimore Ecosystem Study Cary Institute of Ecosystem Studies

2012 BES Annual Meeting Presentation and Poster Abstracts

Effects of Urbanization and Climate on Nitrogen Retention in Coastal Watersheds
Bettez, Neil
Co-Authors: Neil D. Bettez, Peter Groffman, (Cary institute of Ecosystem Studies, Millbrook, NY; 845-677-7600), Jon Duncan, Larry Band (UNC Chapel Hill, Chapel Hill NC, Chapel Hill NC; (919) 962-3921)

Abstract: This study focuses on nitrogen (N) cycling in coastal watersheds with the goal of understanding how urbanization and climate change influence watershed nitrogen retention. This is an important first step in controlling coastal eutrophication. In this study, we calculated the N retention in watersheds with different land uses (urban, suburban, agricultural, and forested) for each year from 1999-2010 by constructing annual input- output budgets. Nitrogen retention was calculated as (N inputs -N outputs)/N inputs. The inputs consisted of N deposited as wet and dry deposition and N applied as fertilizer to crops and lawns while the outputs consisted of N exported in stream flow as nitrate. We used measurements from the nearby NADP (MD 99) and CASTNET (BEL 116) sites in Beltsville MD (~ 50 km away) for annual estimates of wet and dry deposition respectively. For fertilizer inputs we used previously published estimates of fertilizer application from a lawn care survey for lawns and the Maryland Cooperative Extension Service recommended application rates for agricultural. We also compared the annual N retention of each watershed to annual precipitation in order to see how changes in precipitation are related to N retention. N retention ranged from 98-100% in the forested watershed, 55-84% in the agricultural watershed, and 13-94% in the urban/suburban watersheds. In all watersheds N retention decreases with increases in precipitation. Although N retention decreases with urbanization and precipitation, over the next century urbanization is likely to have a larger influence on N export than precipitation.