Response Of Soil Organic Carbon Stability To Grazing And Mowing In Typical Steppe

With the current global focus on "carbon neutrality",how to improve and increase carbon sequestration and reduce carbon emissions has become a hot area of focus for governments and scientists.Soil microbial residue carbon is of great significance for soil carbon fixation.The response of soil microbial residues to utilization methods was more sensitive than that of total soil carbon and had an important impact on the composition and stability of soil carbon.Soil microorganisms are important promoters of soil ecosystem functions.Improving and maintaining soil microbial activity and diversity is conducive to promoting the stability of soil organic carbon and alleviating global environmental changes.In grassland ecosystem,exploring the response of soil microbial community and soil organic matter stability to grazing and mowing utilization has strong theoretical and practical significance for studying the stability of soil organic carbon and its influencing mechanism.In this study,the typical grasslands of Inner Mongolia were selected as the research object,and three comparative experiments of grassland utilization were set up,including different grazing intensity,different mowing frequency and three utilization methods(enclosure,grazing and mowing).By comparing the contents of soil amino sugars,microbial-derived organic carbon and organic matter fractions and their contributions to total soil carbon,the contribution and main influencing factors of soil microbial residues in typical grassland soil under grazing and mowing to organic matter stability fractions and soil carbon were discussed.The main conclusions are as follows:(1)Under different utilization methods,fungal α-diversity and community composition changed significantly with the utilization intensity or methods and were not significantly affected by soil depths.The bacterial α-diversity and community composition changed significantly with soil depth and were not significantly affected by soil utilization.Fungal communities were more responsive to utilization methods than bacterial communities.Compared with changes in microbial phyla,changes in microbial functional groups were more pronounced.(2)Different grazing intensity,mowing frequency and different utilization methods all had significant effects on the non-protection and physical protection fractions of soil organic matter.And mowing was conducive to the accumulation of organic carbon content in the biochemically-protection fraction soil organic matter,that is,the stability of soil organic carbon was affected by grazing and mowing,while the ability of soil to conserve organic carbon was stronger in mowing.(3)Differences in soil microbial residue carbon between all treatments were generally like differences in fungal residue carbon content.Fungal necromass C(accounting for more than 90% of microbial carbon)always contributed more than bacterial necromass C to soil carbon.Soil amino sugar accumulation was affected by fecal and urine input.And fungal residues were more responsive than bacterial residues to utilization methods.Grazing favored an increase in microbial residues to soil carbon.While mowing favored the accumulation of surface soil carbon,the microbial residues to soil carbon decreased.In typical grassland under different utilization methods,soil carbon contained more Glucosamine than Galactosamine and Muramic acid,indicating that fungal residues predominated in all treatments.(4)Soil depth was an important factor for the carbon content in soil microbial residues and soil organic matter fractions and their contribution to total soil carbon accumulation under different grazing intensities and different mowing frequencies.The changes in soil environment and nutrient content of grazing during peak growth season are beneficial to the accumulation of fungal residues and increase soil carbon content.Mowing frequency,on the other hand,increased soil carbon content by affecting the accumulation of fungal residues and active microbial biomass.Therefore,grazing and mowing facilitate the accumulation of total amino sugars and fungal residues in the surface soil.Whether under different grazing intensities or different mowing frequencies,or under three utilization methods(enclosure,grazing and mowing),soil total carbon was positively affected by soil organic matter fractions,and fungal necromass C was significantly affected the carbon content of soil organic matter fractions.