The pattern of soil microbe metabolic limitation and carbon use efficiency was altered by light grazing in typical steppe

Abstract

The influence of grazing on the limiting of soil microbial metabolism is crucial for optimizing grazing management aimed at enhancing the soil's capacity for carbon sequestration in grasslands. Previous studies have investigated the impact of different levels of grazing intensity on the metabolic behavior and carbon utilization efficiency of soil microorganisms. This research aimed to evaluate the microbial biomass levels, physicochemical properties, and the functions of four specific extracellular enzymes associated with the uptake of C, N, and P in a sample plot that exemplifies a typical steppe ecosystem. The study intends to elucidate the dynamics of soil enzyme stoichiometry while identifying the constraints on carbon use efficiency and microbial metabolism in relation to different grazing intensities. The results reveal that in conditions of light grazing, microbial metabolic processes are co-limited by C and P, whereas in ungrazed plots and those subjected to different grazing treatments, limitations are primarily due to C and N. Key determinants of microbial carbon limitation include nutrient availability and the ratio of microbial biomass, while limitations pertaining to N, and P are primarily influenced by microbial biomass levels and their respective ratios. Notably, microbial carbon use efficiency peaked under light grazing conditions. Therefore, sustained light grazing can modify the limitations affecting soil microbial metabolism and enhance microbial carbon use efficiency. This study's outcomes offer a theoretical foundation for developing sustainable grazing management strategies that can improve soil quality and augment the carbon sequestration potential of grasslands.