Beaver Ponds: Resurgent Nitrogen Sinks for Rural Watersheds in the Northeastern United States

Authors

Julia G. Lazar, University of Rhode Island
Kelly Addy, University of Rhode Island
Arthur J. Gold, University of Rhode IslandFollow
Peter M. Groffman
Richard A. McKinney
Dorothy Q. Kellogg, University of Rhode Island

Document Type

Article

Date of Original Version

2015

Department

Natural Resources Science

Abstract

Beaver-created ponds and dams, on the rise in the northeastern United States, reshape headwater stream networks from extensive, free-flowing reaches to complexes of ponds, wetlands, and connecting streams. We examined seasonal and annual rates of nitrate transformations in three beaver ponds in Rhode Island under enriched nitrate-nitrogen (N) conditions through the use of ¹⁵N mass balance techniques on soil core mesocosm incubations. We recovered approximately 93% of the nitrate N from our mesocosm incubations. Of the added nitrate N, 22 to 39% was transformed during the course of the incubation. Denitrification had the highest rates of transformation (97–236 mg N m⁻² d⁻¹), followed by assimilation into the organic soil N pool (41–93 mg N m⁻² d⁻¹) and ammonium generation (11–14 mg N m⁻² d⁻¹). Our denitrification rates exceeded those in several studies of freshwater ponds and wetlands; however, rates in those ecosystems may have been limited by low concentrations of nitrate. Assuming a density of 0.7 beaver ponds km⁻² of catchment area, we estimated that in nitrate-enriched watersheds, beaver pond denitrification can remove approximately 50 to 450 kg nitrate N km⁻² catchment area. In rural watersheds of southern New England with high N loading (i.e., 1000 kg km⁻²), denitrification from beaver ponds may remove 5 to 45% of watershed nitrate N loading. Beaver ponds represent a relatively new and substantial sink for watershed N if current beaver populations persist.

Citation/Publisher Attribution

Lazar, J. G., Addy, K., Gold, A. J., Groffman, P. M., McKinney, R. A., & Kellogg, D. Q. (2015). Beaver Ponds: Resurgent Nitrogen Sinks for Rural Watersheds in the Northeastern United States. J. Environ. Qual., 44(5), 1684-1693. doi: 10.2134/jeq2014.12.0540

Available at: http://dx.doi.org/10.2134/jeq2014.12.0540