HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Walker, J. T. Articles by Geron, C. D. PubMed PubMed Citation Articles by Walker, J. T. Articles by Geron, C. D. Agricola Articles by Walker, J. T. Articles by Geron, C. D. Related Collections Ecosystem Restoration Soil Microbiology Biogeochemical Processes Landscape-Atmosphere Interactions Nutrient Cycling

TECHNICAL REPORTS

Recovery of Nitrogen Pools and Processes in Degraded Riparian Zones in the Southern Appalachians

^a U.S. Environmental Protection Agency, National Risk Management Research Lab., Research Triangle Park, NC 27711
^b USDA Forest Service, Coweeta Hydrologic Lab., Otto, NC 28763

^* Corresponding author (walker.johnt{at}epa.gov).

Received for publication June 5, 2008. Establishment of riparian buffers is an effective method for reducing nutrient input to streams. However, the underlying biogeochemical processes are not fully understood. The objective of this 4-yr study was to examine the effects of riparian zone restoration on soil N cycling mechanisms in a mountain pasture previously degraded by cattle. Soil inorganic N pools, fluxes, and transformation mechanisms were compared across the following experimental treatments: (i) a restored area with vegetation regrowth; (ii) a degraded riparian area with simulated effects of continued grazing by compaction, vegetation removal, and nutrient addition (+N); and (iii) a degraded riparian area with simulated compaction and vegetation removal only (-N). Soil solution NO₃^– concentrations and fluxes of inorganic N in overland flow were >90% lower in the restored treatment relative to the degraded (+N) treatment. Soil solution NO₃^– concentrations decreased more rapidly in the restored treatment relative to the degraded (-N) following cattle (Bos taurus) exclusion. Mineralization and nitrification rates in the restored treatment were similar to the degraded (-N) treatment and, on average, 75% lower than in the degraded (+N) treatment. Nitrogen trace gas fluxes indicated that restoration increased the relative importance of denitrification, relative to nitrification, as a pathway by which N is diverted from the receiving stream to the atmosphere. Changes in soil nutrient cycling mechanisms following restoration of the degraded riparian zone were primarily driven by cessation of N inputs. The recovery rate, however, was influenced by the rate of vegetation regrowth.