Title: Grazing Effects on Net Global Warming Potential in Mixed Grass Prairie Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 30, 2009
Publication Date: July 6, 2009
Citation: Liebig, M.A., Gross, J.R., Kronberg, S.L., Phillips, B.L., Hanson, J.D. 2009. Grazing Effects on Net Global Warming Potential in Mixed Grass Prairie. Meeting Abstract. P. 99. IN: K. Paustian et al. (Eds.) International Symposium on Soil Organic Matter Dynamics Abst. Book. 6-7 July 2009, Colorado Springs, CO. NREL, Ft. Collins, CO. Technical Abstract: Quantification of global warming potential (GWP) for grassland ecosystems is critically important given their vast geographical extent and inherent capacity to affect the global carbon cycle. Contributions of grassland ecosystems to net GWP, however, are largely unknown. In this study, we sought to quantify GWP for two long-term grazing management systems located within a mixed grass biome in south central North Dakota. Grazing management systems included moderately grazed pasture (MGP; 2.6 ha/steer) and heavily grazed pasture (HGP; 0.9 ha/steer), both of which were established on native vegetation in 1916. Factors evaluated for their contribution to GWP included, 1) change in soil organic carbon (SOC) by utilizing 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 both pastures to be significant soil C sinks, with a mean sequestration rate of 0.40 kg C/ha/yr. Cumulative fluxes of methane and nitrous oxide over the measurement period were minor, and not different between pastures. Due to differences in stocking rate, methane production from enteric fermentation was nearly three-fold greater in HGP than MGP. Summation of factors contributing to net GWP indicated both pastures to be net sinks of greenhouse gases to the soil, underscoring the value of grazed, mixed grass prairie to reduce atmospheric radiative forcing.