Study On The Changes Of Soil Nutrients And Plant Community Of Different Stocking Rate Steppe During Stopping Grazing

Inner Mongolia Steppe, an important part of Eurasia Steppe, is not only the foundation of regional development, but also the important environmental barrier. According to the correlativity between soil nutrients and plant community, the paper studies the properties of soil nutrients and plant community during stopping grazing. The results indicate:Heterogeneity of soil nutrients increased under different stocking rates during stoppping grazing, but the proportion of structure factors declined. Biomass and coverage of plant community increased during stoppping grazing, and relative biomass of different plant species and a diversity of plant community also shows different variation. There is an certain correlations between plant community properties and soil nutrients spatial pattern.There existed significant differences from DM decomposition and nutrients release between different successive series species. The rate of DM decomposition and nutrients release from A.chinense is the highest, and P.acaulis is the lowest. Decomposition of and nutrients release from plant litter have significantly (p<0.05) negative correlations with lignin content, C:N ratio, Lignin:N ratio and LigninrP ratio of plant litter, and the C:N ratio is the most important intrinsic factor controlling plant litter decomposition and nutrients release.Lichen is too much sensitive to grazing and trampling, after no grazing for 4 years, there existed no significant difference between lichen biomass under different stocking rate treatment (p>0.05). Under four stocking rate treatment, lichen biomass has negative correlations with plant community coverage and biomass, but significant only in zero stocking rate area (p<0.05). Lichen biomass has significant negative correlations with gramineae plant function group (p<0.05), but no significant negative correlations with legumineae and liliaceae plant function groups (p>0.05). Lichen biomass has significant positive correlations with soil organic carbon and inorganic nitrogen (p<0.05), but no significant positive correlations with soil total nitrogen (p>0.05).In Inner Mongolia Steppe, because of the comprehensive effects of plant properties, soil pH, organic carbon, total N, inorganic N and N mineralization of different plant population patches have different variations.The urea in the urine was rapidly hydrolysed in the soil, and soil pH increased significantly, but as the nitrification proceeded and plant absorbed NH4+-N, soil pH began to decline with time and was significantly (P<0.05) lower than those of the control day 70 and 84 after urine supply. Adding urine increased soil microbial biomass N (MBN) and extractable soil organic N (ESON) and soil dissolved organic carbon (ESOC) concentrations. Urine addition increased soil NH4+-N concentrationsimmediately, but did not increase soil NO3--N concentrations significantly (P<0.05) until day 7. Significant reduction (p<0.05) was observed in the plant biomass and plant N content on days 7, 21 and 35 compared the urine treatment with the control because of herbage being scorched. After day 56, the plant biomass and plant N content from the urine treatment were higher than those from the control, and the differences were significant (p<0.05) on days 70 and 84.