Grazinglands: A Meta-Analysis of Biogeochemical and Soil Physical Responses to Livestock Grazing Regimes.

Grazing lands comprise approximately 40% of the world’s terrestrial surface and have the potential to become degraded due to severe drought or overuse leading to desertification. Soils serve as the backbone of stability and resilience in these systems and provide numerous ecosystem services. We conducted a global analysis of the response of soil organic carbon (SOC), total nitrogen (TN) and bulk density (BD) to livestock grazing systems and intensities from a total of 66 studies that span a range of study durations, climates and environmental conditions. Our results indicate a strong effect of rotational grazing compared to continuous grazing; SOC increased and BD decreased. Continuous grazing compared to no grazing had no effect on SOC or TN and decreased soil C:N (CN) ratio and increased BD. Linear regression revealed that SOC response was driven by grazing intensity, soil depth (cm), % sand and elevation (m) (p < 0.0001, R² = 0.31). We conclude that nutrient cycling and physical characteristics may be driven in part by grazing regimes but other environmental or study variables may be more important predictors. As well, rotational grazing strategies compared to continuous grazing may improve SOC and BD and will require long-term research agendas to determine rotational grazing impacts on grazed ecosystems.