Changes Of Plant Community Characteristics At Different Succession Stage And Its Influence On Soil Properties In Abandoned Cropland

The vegetation restoration is one of the effective step to protect the Loess Plateau from soil erosion and degradation. In order to understand the dynamic of community change between soil property in different plant community of succession stage, the Artemisia capillaries community,Artemisia gmelinii community and Bothriochloa ischaemun community which are typical species in abandoned stage of Loess hilly region were chosen for the research, using the method of substituting spatial difference for time change.From the analysis of vegetation change, soil characteristics, soil aggregates and microorganism under different successional stages in soil profiles. The coordinated variation between vegetation, soil and microorganism in the course of succession was discussed. The main conclusions are as follows:(1) Species rich index ranged from 2.556 ~ 2.858, the range of Shannon index changes to 0.233 ~ 0.312, diversity index range of variation in the 3.540 ~ 4.204, Pielou index range of 1.205 ~ 1.428. Fine roots(<2mm) are the main part of whole roots and most of roots distribute in the upper soil layer. The root biomass, root surface area(RSA) and root length density(RLD) increased with the succession, the SRL andRSA of Bothriochloa ischaemunreflects its ecological strategy in later succession stage. The changes of organic carbon in dominant plant communities were not obvious, and the total nitrogen and total phosphorus showed a decreasing trend with the succession. N:P ranged from 4.53~6.06 less than 14 which showed the vegetation growth was limited by nitrogen in the hilly Loess Plateau region.(2)In addition to soil total phosphorus, soil total nitrogen, organic carbon content shows the characteristics of the surface accumulation, and the performance of the growth trend with the succession. Soil bulk density is decreased with succession, which is different from soil nutrient. In the process of succession, the soil structure was improved, and the nutrient accumulation needed a longer time. There were a higher positive correlation between soil total phosphorus, plant total nitrogen and total phosphorus in the correlation analysis.(3)The soil aggregates stability and the organic carbon and total nitrogen content in it were increased with the succession stage, and decreased with the depth of soil layer and particle size.The highest soil aggregate stability of Artemisia gmelinii community was the highest. In correlation analysis, 0.5~ 2 mm root of surface soil, the biomass, RLD and RSA and soil aggregate R0.25, mean weight diameter(MWD),geometric mean diameter(GMD) and the fractal dimension D has significant correlation, reflects the main function of the fine roots in soil aggregate formation of the turnover process.(4)The α diversity indexes of soil fungal and bacterial communities shows a trend of growth with the succession. Compared with the fungus, the response of bacterial communities to succession was higher, by cluster analysis and principal coordinate analysis of β diversity. Through the T test, the different bacterial species between Artemisia capillaries community,Artemisia gmelinii community is Plantctomycetes. The redundancy analysis is performed on the environmental factors and microbial species factors, and the analysis indicates that soil nutrients and vegetation biomass are the main factors influencing soil microbial community.