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Grazing Management Contributions to Net Global Warming Potential: A Long‐term Evaluation in the Northern Great Plains
Author(s) -
Liebig M. A.,
Gross J. R.,
Kronberg S. L.,
Phillips R. L.
Publication year - 2010
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/jeq2009.0272
Subject(s) - grazing , environmental science , pasture , grassland , primary production , agronomy , greenhouse gas , soil carbon , carbon sink , ecosystem , global warming , fertilizer , climate change , soil water , ecology , biology , soil science
The role of grassland ecosystems as net sinks or sources of greenhouse gases (GHGs) is limited by a paucity of information regarding management impacts on the flux of nitrous oxide (N 2 O) and methane (CH 4 ). Furthermore, no long‐term evaluation of net global warming potential (GWP) for grassland ecosystems in the northern Great Plains (NGP) of North America has been reported. Given this need, we sought to determine net GWP for three grazing management systems located within the NGP. Grazing management systems included two native vegetation pastures (moderately grazed pasture [MGP], heavily grazed pasture [HGP]) and a heavily grazed crested wheatgrass [ Agropyron desertorum (Fisch. ex. Link) Schult.] pasture (CWP) near Mandan, ND. Factors evaluated for their contribution to GWP included (i) CO 2 emissions associated with N fertilizer production and application, (ii) literature‐derived estimates of CH 4 production for enteric fermentation, (iii) change in soil organic carbon (SOC) over 44 yr using archived soil samples, and (iv) soil–atmosphere N 2 O and CH 4 fluxes over 3 yr using static chamber methodology. Analysis of SOC indicated all pastures to be significant sinks for SOC, with sequestration rates ranging from 0.39 to 0.46 Mg C ha −1 yr −1 All pastures were minor sinks for CH 4 (<2.0 kg CH 4 –C ha −1 yr −1 ). Greater N inputs within CWP contributed to annual N 2 O emission nearly threefold greater than HGP and MGP. Due to differences in stocking rate, CH 4 production from enteric fermentation was nearly threefold less in MGP than CWP and HGP. When factors contributing to net GWP were summed, HGP and MGP were found to serve as net CO 2equiv. sinks, while CWP was a net CO 2equiv. source. Values for GWP and GHG intensity, however, indicated net reductions in GHG emissions can be most effectively achieved through moderate stocking rates on native vegetation in the NGP.