Soil Microbial Dynamics Under The Disturbance Background Of Different Logging Periods In The Xiaoxing'an Mountains

As important regulators of ecosystem processes,microorganisms play a crucial role in ecosystem restoration.However,it is unclear how soil microbial communities and functions change during recovery after deforestation.Here,we used high-throughput sequencing technology to systematically analyze the differences in soil microbial community composition,function,and physicochemical properties between primary forests and secondary forests formed after harvesting at different periods.In this experiment,five forest lands with different logging backgrounds were set up in Wuying District,Yichun:forest land with a recovery time of 20 years from2019(T),32 years of forest land(TT),47 years of forest land(FS),61 Years of forest land(SO)and unharvested virgin forest land(O)were used to study the dynamic changes of forest soil microorganisms under different logging backgrounds in the Xiaoxing'an Mountains,in order to provide support for subsequent research on forest soil microbial dynamics.The experimental results are as follows:(1)The soil environmental factors have changed significantly under the disturbance background of different logging periods in the Xiaoxing'an Mountains.With the increase of recovery years after harvesting,the content of soil ammonia nitrogen(NH₄⁺-N)increased from 21.91 mg/kg to 61.43 mg/kg and then decreased to26.23 mg/kg;The content of soil nitrate nitrogen(NO₃^--N)increased from 76.68 mg/kg to 98.84 mg/kg and then decreased to 61.33 mg/kg;Soil total nitrogen(TN)increased from 4.91 g/kg to 5.93 g/kg and then decreased to 5.60 g/kg;Soil ammonia nitrogen(NH₄⁺-N),nitrate nitrogen(NO₃^--N)and total nitrogen(TN)showed a trend of first increasing and then decreasing,but soil ammonia nitrogen(NH₄⁺-N)and total nitrogen(TN)were generally is increasing and nitrate is decreasing.The content of soil total carbon(TC)increased continuously from 80.40 g/kg to 110.42 g/kg;Microbial biomass carbon(MBC)continued to increase from 327.67 mg/kg to 572.92 mg/kg;Microbial biomass nitrogen(MBN)continued to increase from 307.97 mg/kg to619.01 mg/kg;Soil total carbon(TC)and microbial biomass carbon and nitrogen(MBC,MBN)both increased gradually with the restoration of post-cutting forest land.In conclusion,with the increase of post-harvest recovery years,the content of carbon and nitrogen in the soil increased,and other environmental factors did not change significantly.(2)Both bacterial and fungal community compositions changed with the increase of harvesting recovery years,and the bacterial community responded more strongly to the disturbance background in different harvesting periods.The richness and diversity of bacteria showed an increasing trend with the increase of recovery time after harvesting,and the diversity of fungi also increased,but the change of richness was not consistent.(3)The bacterial functional groups related to nitrogen cycle in the bacterial community,such as nitrifying and denitrifying bacterial functional groups,have undergone significant changes.The fungal functional group was significantly increased,and the ectomycorrhizal functional group was significantly decreased.(4)We also found that the responses of bacterial and fungal communities to changes in biomass nitrogen(MBN)were significant(P=0.024<0.05;P=0.028<0.05).The response of bacterial functional groups to changes in biomass nitrogen(MBN)and nitrate nitrogen(NO₃^--N)was significant(P=0.006<0.05;P=0.036<0.05);The response of fungal functional groups to changes in soil water content(SWC)was significant(P=0.002<0.05).To sum up,under the interference background of different logging periods in Xiaoxing'an Mountains,the changes of bacteria are significant,Carbon,nitrogen and water in soil are the main drivers of changes in bacterial and fungal communities and functional groups,Changes in bacterial and fungal community structure and functional taxa will alter soil nutrient cycling during secondary succession.