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Denitrification in Headwater Wetlands with Varying Surrounding Land Cover Types
Citation:
Moon, J., A. Nahlik, D. Wardrop, M. Fennessy, M. Harrison, AND M. Kentula. Denitrification in Headwater Wetlands with Varying Surrounding Land Cover Types. Presented at 2013 Society of Wetland Scientists Annual Meeting, Duluth, MN, June 02 - 07, 2013.
Impact/Purpose:
Wetlands are recognized for their significant role in providing a range of ecosystem services (e.g., recreational opportunities, fishery support, provision of clean water, etc.), which are important for long-term sustainability of communities. We are conducting research to characterize how forcing functions (e.g., climate change and land cover change) affect denitrification, a process that affects the provision of clean water. Denitrification provides a permanent pathway of nitrogen (N) removal from the biosphere through the conversion of N from land-based sources (such as fertilizer and manure) into N gases. This is a desirable process because it removes excess nitrate-N from waters, including those people depend on for drinking water and healthy fisheries; thus, there are human health and economy impacts directly associated with denitrification. Denitrification, however, is not easily measured. Many methods have been proposed and used, each having its own benefits and constraints. Our objectives were to measure denitrification using several of these methods and to determine if denitrification varied with the wetlands’ surrounding land cover types. Our research demonstrates that, for at least one method of measurement, denitrification rates are highest in developed landscapes, followed by urban and forested land cover types. We expect to report and compare results from the other denitrification methods and to apply our findings to wetlands in Oregon, where denitrification research is being conducted this spring and summer.
Description:
Wetlands are recognized for their significant role in providing a range of ecosystem services. In light of this, research is currently being performed to characterize how forcing functions (e.g., climate change and land cover change) affect the provision of ecosystem services by wetlands. Denitrification is an ecosystem service, providing a pathway of nitrogen (N) removal from the biosphere. We assessed denitrification across headwater wetlands in Pennsylvania and Ohio that varied in surrounding land cover. Our objective was to evaluate whether surrounding land cover type affected denitrification rates. We used three methods to estimate denitrification. The acetylene inhibition method and the δ15Ngroundwater tracer push-pull method were used to measure denitrification potential. δ15Nsoil isotopic composition of bulk soil was used as an indicator of long-term N processing. Fall 2011 results suggest that denitrification does vary across land cover types; for example, the push-pull method shows a decrease in denitrification potential rates from developed (203 ± 38 µg-N kg soil-1•day-1) to urban (174 ± 18 µg-N kg soil-1 day-1) to forested (108 ± 16 µg-N kg soil-1•day-1) land cover types. However, we expect that the results are method dependent. We are developing structural equation models for denitrification in wetlands across the land cover gradients, to identify probable forcing functions and to elucidate relationships among stressors associated with land cover and site-level physiochemical properties. Ultimately, we will test the transferability of these models to headwater wetlands with similar land cover types in Oregon.