Divergent effects of moderate grazing duration on carbon sequestration between temperate and alpine grasslands in China

Moderate grazing has been widely proven to improve ecosystem functioning and have profound effects on the carbon cycling and storage in grassland ecosystems, which highly depend on grazing duration and grassland type. However, the effects of moderate grazing durations on carbon sequestration with different grassland types over broad geographic scales across China remain underexplored in the context of striving for carbon neutrality. Here, we explored the probably different responses of carbon sequestration to moderate grazing duration for temperate and alpine grasslands based on 129 published literatures regarding the China's grasslands. The results showed the soil organic carbon stocks were significantly increased during short-term (<5 years) grazing duration, while significantly decreased during medium- (5-10 years) and long-term (≥ 10 years) grazing durations in temperate grasslands. However, the soil organic carbon stocks were significantly decreased during short-term grazing duration, while showed no significant changes during medium- and long-term grazing durations in alpine grasslands. The changes in soil organic stock were significantly positively correlated with the changes in belowground biomass, root:shoot, and microbial biomass carbon (P < 0.05). These findings suggest that the temperate grasslands change from carbon sink to carbon source with moderate grazing duration increasing, while the alpine grasslands present an opposite change pattern from carbon source to carbon sink, regulated by grazing-altered carbon input and microbial activities. Our study might have significant implications for future sustainable management practices for carbon sequestration of China's grasslands.

Plant and soil properties mediate the response of soil microbial communities to moderate grazing in a semiarid grassland of northern China

Even though a growing amount of information about the effects of livestock grazing on soil microbial communities have accumulated in literature, less is known about the combined response of plants, soil properties, and their interactions with soil microbes. In this study, we used a seven-year controlled grazing experiment to quantify the response of plant and soil properties and their interactions with soil microbial communities to moderate grazing in a semiarid grassland of Northern China. Our results showed that moderate grazing reduced the richness and diversity of soil microbial communities, as well as weakened community interactions. However, bacterial communities and their linkages were more stable under moderate grazing than fungal communities. Changes in aboveground plant biomass, soil water content, NO₃^--N, and NO₃/NH₄ ratio dominated grazing effects on soil bacterial communities, while fungal communities were mainly influenced by plant N, soil NO₃^--N, and NO₃/NH₄ ratio. Changes in the plant community composition played a key role in driving the composition of the fungal community. Our results provide a new insight into the response of soil microbes to moderate grazing, and suggest that above- and belowground communities should be considered to be precise indicators of the state and characteristics of the grassland ecosystem.