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Recovery of Nitrogen Pools and Processes in Degraded Riparian Zones in the Southern Appalachians
Author(s) -
Walker John T.,
Vose James M.,
Knoepp Jennifer,
Geron Christopher D.
Publication year - 2009
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2008.0259
Subject(s) - riparian zone , biogeochemical cycle , environmental science , nitrification , cycling , nitrogen cycle , mineralization (soil science) , vegetation (pathology) , nutrient , nutrient cycle , denitrification , riparian buffer , nitrogen , hydrology (agriculture) , environmental chemistry , chemistry , soil science , ecology , soil water , geology , biology , forestry , medicine , geotechnical engineering , organic chemistry , pathology , habitat , geography
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 NO 3 − concentrations and fluxes of inorganic N in overland flow were >90% lower in the restored treatment relative to the degraded (+N) treatment. Soil solution NO 3 − 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.