Soil Organic Carbon Characteristics And Soil Microbial Community Structure Study Of Different Soil Fertility In Fluvo-aquic Soil,North China

Soil organic carbon(SOC),as an important component of terrestrial soil carbon pool,is the key research content of ecosystem carbon cycle.In this study,the representative soils of high,medium,and low fertility different condition in Qihe County,Dezhou City,Shandong Province were used of soil organic carbon mineralization for 196 days with indoor organic carbon culture.Soil physical and chemical factors,soil organic carbon components(Light fraction organic carbon,Heavy fraction organic carbon,microbial biomass carbon,Dissolved organic carbon),soil enzyme activities(urease,invertase,cellulase,catalase)and microbial community structure were studied to provide scientific basis and data support for the management of soil carbon pool and global carbon cycle process in Fluvo-aquic soil,North China by revealing the changes of soil organic carbon composition and mineralization under different soil fertility conditions and understanding the changes of soil microbial community structure and diversity.The main results are as follows:(1)With the increase of soil fertility grade,soil nutrient content increased significantly(P < 0.05).Under the same soil fertility condition,the soil nutrient content in 0~20 cm soil layer was significantly higher than that in 20~40 cm soil layer(P< 0.05).Two-factor analysis shows that there was no coupling relationship between soil fertility grade and soil depth on soil physical and chemical factors.(2)Under different soil fertility conditions,soil organic carbon components are different.The contents of recombinant organic carbon(HFOC),microbial biomass carbon(MBC)and soluble organic carbon(DOC)in soil were significantly different(P < 0.05).Under the same soil fertility,the contents of HFOC,MBC and DOC in 0~20 cm soil layer were significantly higher than those in 20~40 cm soil layer(P < 0.05).The contents of HFOC,MBC and DOC in soil were affected by various soil nutrient contents.(3)Under different soil fertility conditions,soil urease,invertase,cellulase and catalase activities were significantly different(P < 0.05),showing the tendency of high soil fertility(HSF)> medium soil fertility(MSF)> low soil fertility(LSF).Under the same soil fertility,the activities of soil enzymes in 0~20 cm soil layer were significantly higher than those in 20~40 cm soil layer(P < 0.05).Different soil enzymes not only played their respective roles,but also had close relationship with each other.(4)The regularity of soil organic carbon mineralization declined rapidly in the early stage of incubation and stabilized in the later stage.The cumulative amount of soil organic carbon mineralization showed significant difference under different soil fertility conditions(P < 0.05).Among them,the stability of low fertility conditions soil was the worst,which is not conducive to the fixation of soil organic carbon.Under the same geodynamic condition,the mineralization rate and accumulation of soil organic carbon decreased significantly with the deepening of soil depth in vertical distribution(P<0.05).Soil organic carbon mineralization was affected by many factors,such as soil physical and chemical factors.With the process of soil organic carbon mineralization,MBC and DOC are significantly lower than the initial content(P < 0.05).(5)Under different soil fertility conditions,there are large differences in the amount of litter,soil nutrient content and root exudates in the soil,which lead to a large difference in soil microbial population structure and quantity.Under the same soil fertility condition,different soil layers can change the structure of soil microbial community,and there are obvious differences.