Response Of Organic Carbon In Mineral Soil To Climate Change In Permafrost Wetland Of The Great Hing’an Mountains

Permafrost wetland soil in the Northern Hemisphere is important organic carbon pool for terrestrial ecosystems.With the increase of temperature and the degradation of permafrost,the mineralization of soil organic carbon in permafrost wetlands will be significantly affected,and mineral protection can slow down the response of soil organic carbon mineralization to warming.The Great Hing’an Mountains is located at the southern edge of the zonal permafrost distribution area of Eurasia,and the wetland type is mainly swamp wetland.Due to the significant warming trend in recent decades,the Great Hing’an Mountains has received widespread attention.However,the current research on the warming response of soil organic carbon in permafrost wetlands mainly focuses on surface organic soil,and the stability and warming response of mineral soil organic carbon in permafrost areas need to be strengthened.In this study,we selected the swamp wetlands in the northern part of the Great Hing’an Mountains as the research object,combined with indoor incubation experiments and isotopic analysis,to explore the response mechanism of mineral soil organic carbon to climate change in wetlands,in order to provide basic data and theoretical support for predicting the change trend and intensity of soil organic carbon in swamp wetlands in permafrost areas.The main conclusions are as follows:（1）Soil Fe/Al oxides could adsorb active organic carbon with a low degree of decomposition,so that mineral soil organic carbon remained stable for a long time.HF-OC was the main organic carbon component,with an average content of about 83.26%of the bulk soil organic carbon,which enriched the main parts of easily oxidized organic carbon and dissolved organic carbon.The content of Fe/Al oxides in the subsoil was significantly positively correlated with the soil organic carbon content and negatively correlated with the soilδ¹³C value,which confirmed that Fe/Al oxides could effectively adsorption,decompose and transform active organic carbon with a low degree of transformation.（2）Temperature increase promoted the soil organic carbon mineralization in permafrost wetlands,but mineral protection could slow the response of soil organic carbon to warming and reduce the temperature sensitivity of soil organic carbon.Soil fraction,temperature and depth all had significant effects on cumulative soil CO₂emissions,and there were interactions between the three.After warming of 10°C,the increase in topsoil organic carbon mineralization was on average about 2.53 times that of subsoil.The response of subsoil to warming was low,and warming did not have a significant effect on microbial abundance in subsoil.The temperature sensitivity of soil organic carbon was significantly negatively correlated withδ¹³C value and the ratio of mineral content to organic carbon content.（3）Soil moisture could promote the soil organic carbon mineralization in permafrost wetlands by increasing microbial activity,but it had no significant effect on soil organic carbon temperature sensitivity.Soil moisture was positively correlated with the carbon content of microbial biomass in soil.Temperature,soil moisture and depth all had significant effects on cumulative soil CO₂ emissions,and there were interactions between the three.Under the incubation condition of 0-40%WHC,soil moisture had a significant promoting effect on soil organic carbon mineralization.However,under the incubation conditions of 5°C and 40-100%WHC,soil moisture did not have a significant effect on soil organic carbon mineralization.