Effects Of Fire Originated Black Carbon On Ectomycorrhizal Fungi Community And Soil Carbon Pool Stability In Larix Gmelini Forest

Fire is one of the important disturbance factors in boreal forest ecosystems,and black carbon,as a product of fire,is widely present in forest soils.Although black carbon has a positive impact on tree growth,little is known about the synergistic effects between black carbon and microorganisms that promote tree growth,such as mycorrhizal fungi.As a bridge between coniferous tree species and soil in the boreal forest ecosystem,ectomycorrhizal fungi（ECM）play a significant role in the decomposition and fixation of soil organic carbon.Exploring the changes in the ectomycorrhizal fungal community after fire can provide a theoretical basis for the restoration and scientific management of the carbon pool in the boreal forest ecosystem after fire.This study took Larix gmelinii forest in Da Hinggan Mountains as the research object,using high-throughput sequencing methods to identify ECM fungi,and explore the changing characteristics and key influencing factors of ECM fungal community under fire and black carbon addition during the growth season;The physical grouping of soil organic carbon was conducted,and the effects of different treatments on the physical composition of organic carbon were studied to clarify the mechanism of ECM fungal community in it.The research results show that:（1）During the growing season,soil physical and chemical properties showed significant seasonal changes.After fire interference,soil moisture,total phosphorus（TP）,ammonium nitrogen（NH₄⁺-N）,organic carbon（SOC）,dissolved organic carbon（DOC）,microbial biomass carbon（MBC）,and mineral bound organic carbon（MAOC）contents significantly increased,while soil p H significantly decreased（p<0.05）.After adding black carbon,soil p H,total soil organic carbon（SOC）,free particulate organic carbon（f POC）,and MAOC content significantly increased,while soil NH₄⁺-N,nitrate nitrogen（NO₃^--N）,and DOC content significantly decreased（p<0.05）.（2）During the growing season,the abundance andαThe diversity decreased significantly,while the black carbon addition treatmentαThe diversity increased significantly（p<0.05）.However,fire treatment had a significant impact on the increase in species abundance of Basidiomycetes,while black carbon addition treatment had a significant impact on the increase in species abundance of Ascomycetes.The composition of ECM fungi community in both fire and black carbon addition treatments was significantly affected by the content of MBC,NH₄⁺-N,TN,and TP in the soil.This study showed that fire reduced the diversity of ECM fungi in the growing season of Larix gmelinii forest,and significantly reduced its abundance.However,the addition of black carbon after fire promotes the recovery of ECM fungi and increases their diversity by affecting soil microorganisms and soil nitrogen content.（3）During the growing season,soil particulate organic carbon（POC）in the burning and black carbon addition treatments is positively correlated with soil TN and TP,and negatively correlated with soil MBC,while soil MAOC is positively correlated with soil p H and available nitrogen,indicating that the decomposition and fixation of soil organic carbon are closely related to microbial activity.The results of this study also indicate that soil p H,TN,available nitrogen,MBC,and ECM fungal communities are important variables that affect soil organic carbon stability,with interpretation rates of 14.6%,41.8%,24.6%,36.4%,and 43.2%,respectively.Basidiomycetes in ECM fungal communities are important variables for predicting soil f POC and o POC content,while ascomycetes are important variables for predicting soil MAOC content.In addition,due to the different retention times of black carbon in soil,the ECM fungal community after fire is mainly related to the content of MAOC in the soil,while the black carbon addition treatment is mainly related to the content of closed organic carbon（o POC）in the soil.Therefore,burning and black carbon addition can affect the stability of soil organic carbon pools by affecting the composition of ECM fungal communities.