The Vertical Distribution And Influencing Factors Of Soil Microbial Biomass And Community Structure In Huabaowan Landslide Reservoir And Check Dam

The species and biomass of soil microbes could reflect the changes of ecological environment in soil.Present studying of the check dam microbes focused on the topsoil,and the studying of soil profile microbes less.In order to clarifying the main influencing factor of the biomass and characteristics of soil microbial community structure in the Loess Plateau.We studied the distribution of the biomass and community structure of landslide reservoir and man-made check dam in soil profiles,and discussed correlations between them with the chemical components and mechanical compositions.On this basis,the preliminary results were observed as the followings:(1)According to the data of mechanical compositions,It can be divided into 5 depositional cycles in the vertical direction of the soil profiles in landslide reservoir,but it can be divided into 25 depositional cycles in check dam.It is based on sand of the soil profiles in landslide reservoir(56.62%),it is based on silt of the soil profiles in check dam(46.39%).(2)The contents of SOC,TN,MBC and MBN have the consistent distribution in the vertical direction in landslide reservoir,A profile>B profile>C profile in the horizontal direction.The contents of SOC,TN,MBC and MBN shows the distribution that the fine particle layers>the coarse particle layers in check dam.(3)It is detected total 17 kinds of phospholipid fatty acidsin landslide reservoir,20 kinds of phospholipid fatty acids in check dam.Whether landslide reservoir or check dam,bacteria is the main composition of the soil microbial community in two dams(respectively accounts for about 65%-75%,60%-71%),following by actinomycetes(15%-25%,10%-25%)and fungi(5%-10%,12%-20%).(4)Judging from the biomass of microbes,soil profiles include three high-value areas(0-50cm,120-140cm and 220-260cm)and three low-value areas in landslide reservoir,that the distribution is A profile>B profile>C profile in the horizontal direction.The distribution of the contents of soil microbes,bacteria,fungi and actinomycetes is the fine particle layers>the coarse particle layers.(5)The trendencies of the change of microbial diversity indexes(Shannon index,Simpson index and Pielou index)are the basically same.In the vertical direction,the three microbial diversity indexes in high-value areas are basical higher than that in low-value areas in landslide reservoir,A profile>B profile>C profile in the horizontal direction.The distributions of microbial diversity indexes in check dam were both the fine particle layers>the coarse particle layers.(6)Soil clay component is the main factor that influences on the microbial biomass and community structure.The total microbial biomass,the bacterial biomass and the fungal biomass have significantly positive correlations with the clay content.With respect to landslide reservoir,correlation coefficient r is 0.58,0.57 and 0.62(P<0.05),respectively.With respect to check dam,r is 0.94,0.97 and 0.98(P<0.001),respectively.