Science Inventory

Relative importance of landscape versus local wetland characteristics for estimating wetland denitrification potential

Citation:

Russell, M., R. Fulford, K. Murphy, C. Lane, J. Harvey, D. Dantin, F. Alvarez, J. Nestlerode, A. Teague, M. Harwell, AND A. Almario. Relative importance of landscape versus local wetland characteristics for estimating wetland denitrification potential. WETLANDS. The Society of Wetland Scientists, McLean, VA, 39(1):127-137, (2019). https://doi.org/10.1007/s13157-018-1078-6

Impact/Purpose:

There is a lack of full quantitative understanding of factors controlling denitrification across different scales and landscape types although existing research suggests that interactions among hydrology, geomorphology, and nitrogen loading are the dominant controls. We compared local, site-scale characteristics to denitrification potentials measured as denitrification enzyme activity (DEA) in a set of wetlands grouped by wetland type and land use in their local drainage basin in order to explore the relative importance of landscape and site-scale factors for determining nitrogen removal rates. When site and landscale-scale explanatory factors were combined using step-wise multiple linear regression, two soil and one drainage basin characteristic (Soil NO3, Soil Percent N, and Percent Agriculture) were identified as having significant (p<0.001, r2 = 0.77) correlations with mean DEA rates. Our results suggest that DEA is controlled mainly by local-scale site wetland characteristics but more work will be needed to tease out the interdependencies and relative importance among these and potentially related landscape-scale factors.

Description:

Rapid urban growth is the main driver of stressors on ecosystem services for the Tampa Bay region of Florida, U.S.A. wherein the effects of increased reactive nitrogen (Nr) loading due to a growing human population have been given prominent attention. Frequent anoxic conditions, high concentrations of labile carbon, and the presence of facultative microbes and available nitrogen sources, allow wetlands to act as significant sinks for Nr, with denitrification a major pathway that results in the release of N2 gas back to the atmosphere. There is a lack of full quantitative understanding of factors controlling denitrification across different scales and landscape types although existing research suggests that interactions among hydrology, geomorphology, and nitrogen loading are the dominant controls. We compared local, site-scale characteristics with denitrification potentials measured as denitrification enzyme activity (DEA) in a set of wetlands grouped by wetland type and land use in their local drainage basin in order to explore the relative importance of landscape and site-scale factors for determining nitrogen removal rates. Local-scale soil characteristics differed between sites with high (0.79±0.10 standard error (SE)) and low (0.09±0.01 SE) DEA rates (µg N gdw-1 hr-1). Sites with higher DEA rates had significantly higher percentages of carbon, nitrogen, concentrations of soil extractable NO3 and percent loss on ignition. At the landscape-scale, sites with upstream agricultural activity (>44% Agricultural and 31% Urban lands) (0.24±0.07 SE µg N gdw-1 hr-1). When site and landscape-scale explanatory factors were combined using step-wise multiple linear regression, two soil and one drainage basin characteristic (Soil NO3, Soil Percent N, and Percent Agriculture) were identified as having significant (p<0.001, r2 = 0.77) correlations with mean DEA rates. Our results suggest that DEA is controlled mainly by local-scale site wetland characteristics but more work will be needed to determine the interdependencies and relative importance among these and potentially related landscape-scale factors.