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Journal of Environmental Quality Abstract - Wetlands and Aquatic Processes

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

 

This article in JEQ

  1. Vol. 44 No. 5, p. 1684-1693
    unlockOPEN ACCESS
     
    Received: Dec 17, 2014
    Accepted: May 29, 2015
    Published: September 16, 2015


    * Corresponding author(s): agold@uri.edu
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doi:10.2134/jeq2014.12.0540
  1. Julia G. Lazara,
  2. Kelly Addya,
  3. Arthur J. Gold *a,
  4. Peter M. Groffmanb,
  5. Richard A. McKinneyc and
  6. Dorothy Q. Kellogga
  1. a Dep. of Natural Resources Science, Univ. of Rhode Island, One Greenhouse Rd., Kingston, RI 02881
    b Cary Institute of Ecosystem Studies, Box AB, Millbrook, NY 12545
    c Atlantic Ecology Division, US Environmental Protection Agency, 27 Tarzwell Dr., Narragansett, RI 02882
Core Ideas:
  • In rural watersheds of southern New England with high N loading, denitrification from beaver ponds may remove 5–45% of watershed nitrate-N loading.
  • Beaver ponds represent a relatively new, substantial sink for watershed N if current beaver populations persist.
  • Denitrification had the highest rates of nitrate transformation in our beaver pond study, with N2 as the dominant product.

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.

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