Simulating Grazing Effects on Soil Organic Carbon Dynamics in Semi-arid Rangelands (Southern Iran)

Abstract Grazing is one of the main causes of rangeland degradation worldwide, due to the effects of overgrazing on vegetation cover and biodiversity. But few data are available on the effect of grazing intensity on the dynamics of soil organic carbon (SOC) and soil labile organic carbon (SLOC). So far, very few studies have addressed the modeling of SOC dynamics under different grazing intensities, and SLOC dynamics has not been modeled yet. In this study, we used the CENTURY model to select the most effective grazing management in terms of carbon sequestration (SOC and SLOC stocks) in semi-arid rangelands of Southern Iran. The effect of four different scenarios of grazing intensity was simulated: no grazing, light grazing (LG), moderate grazing (MG), and heavy grazing (HG). The results of long-term model simulations (2015–2100), indicated that SOC stocks will change by 2.7, 1.7, -23.4, and − 24.6% in the scenarios of exclusion, LG, MG, and HG respectively compared to 2014. With increasing grazing intensities, SLOC stocks in LG, MG, and HG scenarios significantly decreased compared to the no grazing scenario by 26.1, 59.6, and 70%, respectively. Thus, this study suggests recommending light grazing management for semi-arid rangelands of Iran and also SLOC as a suitable index for studying the effect of grazing on soil carbon.