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Grazing management, season, and drought contributions to near-surface soil property dynamics and greenhouse gas flux in semiarid rangeland

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Semiarid rangelands provide an array of ecosystem services, yet the role of grazing management and environmental conditions to affect rangeland soil function is poorly understood. A study was conducted to assess effects of grazing management, season, and drought on soil property dynamics and greenhouse gas (GHG) flux within semiarid rangeland. Grazing management treatments evaluated in the study included two native vegetation pastures differing in stocking rate [moderately and heavily grazed pastures (MGP and HGP, respectively)] and a fertilized, heavily grazed crested wheatgrass [Agropyron desertorum (Fisch. ex. Link) Schult.] pasture (CWP) near Mandan, ND, USA. Over a period of three years, soil properties were measured in the spring, summer, and fall at 0-5 and 5-10 cm, while soil-atmosphere fluxes of carbon dioxide, methane, and nitrous oxide were measured annually on one to two week intervals. High stocking rate and fertilizer N application within CWP contributed to increased soil bulk density and extractable N, and decreased soil pH and microbial biomass compared to native vegetation pastures. Soil nitrate-N tended to be greatest at peak aboveground biomass, whereas soil ammonium-N was greatest in early spring. Drought conditions during the third year of the study contributed to nearly two-fold increases in extractable N under CWP and HGP, but not MGP. Stepwise regression found select soil properties to be moderately-related to soil-atmosphere GHG fluxes, with model r-square ranging from 0.09 to 0.76. Among soil properties, electrical conductivity was included most frequently in stepwise regressions. Soil attributes measured in this study suggest high stocking rate combined with long-term fertilizer N application may compromise soil functions necessary to support and regulate key ecosystem services in semiarid rangeland.
M. A. Liebig , S. L. Kronberg , J. R. Hendrickson , J. R. Gross
USDA Scientist Submission
Rangeland ecology & management 2014 May v.67 no.3
the Society for Range Management
Journal Articles, USDA Authors, Peer-Reviewed
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