Effects Of Warming And Fencing On Soil Organic Carbon Components In Alpine Grassland

In the context of climate warming,fencing sealing is a common grassland ecosystem management method.Fencing mainly prevents livestock from entering the grassland,reducing grazing and trampling pressure,improving degraded grassland plant structure,increasing species diversity,improving grassland productivity,improving soil structure,increasing nutrient content,increasing soil microbial biomass and enzyme activity,and gradually achieve grassland restoration.Clarifying the accumulation process of soil organic carbon under warming and fencing is crucial for understanding the carbon source-sink effect in grassland ecosystems.In this study,the soil organic carbon components and their influencing factors under warming and fence sealing were selected for 15 consecutive years.By understanding the sources and accumulation of soil organic carbon in alpine grassland ecosystems,calculating the contribution of fungi and bacteria to microbial residue carbon,analyzing the relative contribution of microbial-derived carbon to organic carbon accumulation,and clarifying the relationship between environmental factors and microbial residue carbon under warming and fencing in alpine grassland areas,we can understand the role of microorganisms in soil organic carbon accumulation,providing a scientific basis for ecosystem management and conservation.This study is of great significance for revealing the carbon cycling and storage mechanisms of this ecosystem.The main conclusions are as follows:(1)The p H and conductivity of soil showed significant changes with soil depth under the warming + fencing and fencing treatments,while there was no significant change in the p H and conductivity of soil in the control area with soil depth.Soil moisture content decreased significantly with increasing soil depth under the warming + enclosure,fencing treatments and control area.The soil in the warming + enclosure,fencing treatments and control area was dominated by silt and sand particles,with the highest proportion of silt particles and the lowest proportion of clay particles.There was no significant difference in particle distribution among the soil under the warming + enclosure,fencing treatments and control area.(2)Soil organic carbon(SOC)and total nitrogen(TN)showed a significant decrease with increasing soil depth under the warming + enclosure,fencing treatments and control area.At the same soil depth,the carbon-nitrogen ratio of the soil under the warming + fencing treatment and control area was significantly higher than that of the soil under the fencing treatment.p H showed a negative correlation with conductivity,but showed no significant correlation with other soil indicators.Conductivity,moisture content,SOC,TN,and carbon-nitrogen ratio showed a positive correlation with each other.(3)The activities of all five enzymes showed a decreasing trend with increasing soil depth under the warming + enclosure,fencing treatments and control area.There were differences in the activities of the five enzymes at the same soil depth under the warming +fencing treatment,fencing treatment,and control area,but the overall difference was not significant(p>0.05).(4)The correlation analysis between soil enzyme activities and warming + fencing and fencing treatments showed that alkaline phosphatase activity was significantly positively correlated with total nitrogen and soil organic carbon,and significantly negatively correlated with soil depth(p<0.05).Urease activity was significantly positively correlated with TN,SOC,soil moisture content,and conductivity,and significantly negatively correlated with p H and soil depth(p<0.05).Sucrase activity was significantly positively correlated with TN,SOC,soil moisture content,and conductivity,and significantly negatively correlated with p H and soil depth(p<0.05).Peroxidase activity was significantly positively correlated with TN,SOC,soil moisture content,and conductivity,and significantly negatively correlated with soil depth(p<0.05).(5)Compared with the control,there was no significant difference in bacterial and fungal residue carbon under the warming + fencing and fencing treatments.However,fungal residue carbon contributed more to soil organic carbon than bacterial residue carbon.The total amount of amino sugars in the soil was not significantly affected by the warming + fencing and fencing treatments compared with the control.However,the treatments significantly reduced the long-term turnover of microbial residue carbon in the soil,while the short-term turnover was not significant.(6)Total amino sugars,fungal residue carbon,bacterial residue carbon were significantly positively correlated with conductivity,moisture content,soil organic carbon(SOC),and total nitrogen(TN).In summary,warming will reduce the contribution of microbial source carbon to soil organic carbon,fence sealing increases the contribution of microbial source carbon to soil organic carbon,0-30 cm soil layer depth,microbial residual carbon contribution of more than48.6%.Fungal residual carbon contributes more to soil organic carbon than bacterial residual carbon.Total amino sugars,fungal residual carbon,and bacterial residual carbon were significantly positively correlated with conductivity,moisture content,soil organic carbon and total nitrogen.