Grazing improves C and N cycling in the Northern Great Plains: A meta-analysis
Citation
Wang, X., McConkey, B.G., VandenBygaart, A.J., Fan, J., Iwaasa, A., Schellenberg, M. (2016). Grazing improves C and N cycling in the Northern Great Plains: A meta-analysis. Scientific Reports, [online] 6 http://dx.doi.org/10.1038/srep33190
Plain language summary
Livestock grazing affects the storage and cycling of carbon (C) and nitrogen (N) in grassland. The direction and size of the effects is poorly understood for grasslands in the Northern Great Plains (NGP). We analyzed the results from available studies to determine the response of 30 variables of the storage and flows of C and N to grazing for NGP grasslands. The results showed that grazing increased soil C by 5% and N by 11% in the topsoil. Grazing stimulated decomposition of surface plant litter. Grazing also increased the release of plant-available soil N forms of ammonia and nitrate. Our results indicate that sustainable grazing management practices have increases soil C and N over the past 70 to 80 years. We believe this represented the recovery of C and N lost during a period of widespread grassland deterioration that occurred in the first half of the 20th century. The increased soil C in grassland soils has offset some of the emissions of greenhouse gases.
Abstract
Grazing potentially alters grassland ecosystem carbon (C) and nitrogen (N) storage and cycles, however, the overall direction and magnitude of such alterations are poorly understood on the Northern Great Plains (NGP). By synthesizing data from multiple studies on grazed NGP ecosystems, we quantified the response of 30 variables to C and N pools and fluxes to grazing using a comprehensive meta-analysis method. Results showed that grazing enhanced soil C (5.2 ± 4.6% relative) and N (11.3 ± 9.1%) pools in the top layer, stimulated litter decomposition (26.8 ± 18.4%) and soil N mineralization (22.3 ± 18.4%) and enhanced soil NH4+ (51.5 ± 42.9%) and NO3- (47.5 ± 20.7%) concentrations. Our results indicate that the NGP grasslands have sequestered C and N in the past 70 to 80 years, recovering C and N lost during a period of widespread grassland deterioration that occurred in the first half of the 20th century. Sustainable grazing management employed after this deterioration has acted as a critical factor for C and N amelioration of degraded NGP grasslands and about 5.84 Mg C ha-1CO2-equivalent of anthropogenic CO2 emissions has been offset by these grassland soils.