Title: Grazing Management Contributions to Net Global Warming Potential: A Three Year Evaluation in the Northern Great Plains Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 20, 2009
Publication Date: November 5, 2009
Citation: Liebig, M.A., Gross, J.R., Kronberg, S.L., Phillips, B.L., Hanson, J.D. 2009. Grazing Management Contributions to Net Global Warming Potential: A Three Year Evaluation in the Northern Great Plains. Meeting Abstract. Technical Abstract: Determination of grassland ecosystems as net sinks or sources of greenhouse gases is limited by a paucity of information regarding management impacts on the flux of nitrous oxide and methane. Furthermore, no long-term evaluation of net global warming potential (GWP) for grassland ecosystems in the northern Great Plains (NGP) of North America have been reported in the literature. Given this need, we sought to determine net GWP for three grazing management systems located within the NGP, a region possessing a semi-arid continental climate and abundant grassland resources. Grazing management systems included two native vegetation pastures [moderately grazed pasture (MGP), heavily grazed pasture (HGP)] and a crested wheatgrass pasture (CWP) near Mandan, ND. Factors evaluated for their contribution to GWP included, 1) change in soil organic carbon (SOC) through utilization of archived soil samples, 2) flux of methane and nitrous oxide over the three year period using static chamber methodology, and 3) literature-derived estimates of methane production for enteric fermentation. Analysis of SOC over a 44 yr period indicated all pastures to be significant soil C sinks, with C sequestration rates ranging from 0.39 to 0.46 Mg C/ha/yr. All pastures were minor sinks for methane, with uptake rates <2.0 kg C/ha/yr. Annual N fertilizer application within CWP contributed to cumulative nitrous oxide emission over two-fold greater than that observed in HPG and MGP. Due to differences in stocking rate, methane production from enteric fermentation was nearly three-fold greater in CWP and HGP than MGP. Summation of factors contributing to net GWP indicated HGP and MGP to be net sinks of greenhouse gases to the soil, underscoring the value of grazed, mixed grass prairie to reduce atmospheric radiative forcing.