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This article in SSSAJ

  1. Vol. 74 No. 5, p. 1826-1833
     
    Received: Dec 21, 2009


    * Corresponding author(s): burginam@gmail.com
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doi:10.2136/sssaj2009.0463

Factors Regulating Denitrification in a Riparian Wetland

  1. Amy J. Burgin *ab,
  2. Peter M. Groffmana and
  3. David N. Lewisa
  1. a Cary Institute of Ecosystem Studies, Box AB, Millbrook, NY 12545
    b currently at, 60 Brehm Lab. Dep. of Earth and Environmental Sciences, Wright State Univ. 3640 Colonel Glenn Hwy. Dayton, OH 45435

Abstract

Soil O2 is an important regulator of microbial processes but is rarely measured. Consequently, our understanding of temporal and spatial variation in soil O2 is limited. This, in turn, limits our understanding of a key regulator of N loss through microbial denitrification. In this study, we explored: (i) how soil O2 varied seasonally in wet and dry riparian areas, (ii) how this variation in O2 exposure translated into spatially heterogeneous areas of denitrification and denitrification potential, and (iii) how O2, NO3 , and moisture interacted to affect denitrification rates. We collected continuous measurements of soil O2 in “wet” and “dry” riparian soils and measured denitrification by removing the background N2 headspace from intact soil cores, replacing it with a He–O2 mixture, and measuring N2 production with time. We found that soil O2 varied considerably in the wet site, ranging from anoxic conditions when the water table was high in late spring to completely oxic conditions (20% O2) during summer when the water table dropped. In contrast, the dry site remained at 20% nearly year round. Bulk soil O2 strongly controlled denitrification rates in the wet site but not in the dry site, which only denitrified when NO3 was added. Denitrification enzyme activity was approximately twice as high in the wet site compared with the dry site, both of which responded predictably to O2 exposure. Experimental manipulation of O2, NO3 , and C may help to identify real hot and cold spots for denitrification in landscapes.

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