Community Structure Of Soil Fauna And Its Effects On Leaf Litter Decomposition Under Nitrogen Deposition

Nitrogen depositionhas been a threat to global biodiversity and ecosystems.It has become a global ecological problem.In order to study the effects of nitrogen addition on soil fauna community structure and litter decomposition,different treatments of nitrogen addition including0,5,10,15,30 g N·m-2·a-1were set up in poplar plantations.Litterbags with 3 different mesh sizes?0.01mm,1mm,5mm?were set up under five different treatment of nitrogen.Soil fauna community structure in the litterbags,soil fauna community structure of topsoil?0-10cm?,mass remaining rate,physical and chemical properties of topsoil?0-10cm?are measured within 6month?Feb,Apr,Jun,Aug,Oct,Dec?.The main results are as follows:?1?The individual density and group number of soil fauna in the litterbags increased at the concentration of N3,The dominant groups in the litterbags were Oribatida,Prostigmata,Isotomidae;The individual density of the soil fauna in the macro-mesh?5mm?litterbags was higher than meso-mesh?1mm?litterbags;The group number of soil fauna in the macro-mesh litterbags was higher than meso-mesh litterbags,The Pielos index of the soil fauna community in the meso-mesh litterbags was higher than that of in the macro-mesh litterbags,The Marglef index of the soil fauna community in the macro-mesh litterbags was higher than meso-mesh litterbags;The Simpson index and Shannon-Wiener index of the soil fauna community in the macro-mesh litterbags were higher than meso-mesh litterbags except June and August.?2?After one year's decomposition,the mass remaining rates were 0.01mm?52.29%?>1mm?49.85%?>5mm?47.96%?,nitrogen deposition did not change this pattem;The mass remaining rate under N3 treatment was less than other nitrogen treatments,and the mass remaining rate was significantly correlated to the group number of soil fauna?p<0.01?.The mass remaining rate in the meso-mesh litterbags was significantly correlated to the Shannon-Wiener index and the Marglef index?p<0.05?.The mass remaining rate in the macro-mesh litterbags significantlycorrelated to the Shannon-Wienerindex and the Marglef index under N3 treatment.?3?N3treatment increased the individual density and group number of soil fauna in the topsoil?0-10cm??p<0.05?,and N4treatment decreased the individual density and group number of soil fauna in the topsoil.The content of NO₃^--N and SOC in the topsoil increasedwith the addition of nitrogen.The content of MBC was highest in the early spring?April?.The individual density of soil fauna in the topsoil?0-10cm?was significantly correlated to the content of SOC at t N1?N2 treatments.The individual density of soil fauna in the topsoil?0-10cm?was significantly correlated to the content of MBC in the topsoil?0-10cm?except N4 treatment?p<0.05?.Basically,the individual density and group number of soil fauna increased at N3 treatment.The mass remaining ratehas a significantly negative correlation with group number,Shannon-Wiener index and Marglef index of soil fauna?p<0.05?,which reveals that the diversity and richness of the soil fauna is beneficial to the litter decomposition,also to nutrient cycling,This study revealed the effect of nitrogen deposition on soil fauna community structure and its effect on litter decomposition,which provided an important basis for clarifying the mechanism of the ecological process on the productivity of poplar plantation.