Get reliable rangeland science

Grazing represents a multifaceted interaction between livestock and grasslands, encompassing three main mechanisms: defoliation, dung and urine return, and trampling, each of which profoundly affects soil carbon (C) storage processes. To better understand the impact of grazing on soil C dynamics, we conducted an in-situ 13C pulse labeling experiment on a field-simulated grazing platform, incorporating separate or combined treatments of defoliation, excreta return, and trampling. We tracked 13C allocation in dissolved organic carbon (DOC), microbial biomass carbon (MBC) and soil organic carbon (SOC). We found that mowing significantly promoted the accumulation of root-derived DOC and MBC. Trampling also increased root-derived DOC. A positive correlation was observed between root-derived DOC and MBC, whereas no significant correlation was found between root-derived SOC and either root-derived DOC or MBC. Overall, we disentangled the complex grazing behaviors, quantified and tracked the pathways of C among different C pools under different grazing disturbance. Our study also highlights the distinct impact of mowing, trampling, and dung and urine return by ungulates on SOC, and future research should thoroughly consider these mechanisms to improve grassland management practices.