Studies On Effect Of Living Sand Barrier Vegetation And Soil Restoration In Horqin Sandy Land

China is one of the countries suffering the most serious damage caused by land desertification in the world. Along with the implementation of sand prevention and control project, large area of artificial vegetation and large amount of biomass resources are cultivated at the same time of controlling and improving ecological environment in the sandy area. In recent years, degradation and death of large area of vegetation has exerted direct impact to the sustainable effect of the artificial vegetation. Therefore, enhancing management and utilization of artificial vegetation has become a critical issue that needs to be addressed within a period in the future. Aiming at the artificial vegetation cultivated in controlling shifting sand dunes with living sand barriers widely applied in Horqin sandy land, guided by the modern vegetation ecology and restoration ecology and adopting the means of combining field investigation and indoor analysis, we conduct this comprehensive study on the effect of vegetation and soil restoration so as to master comprehensively its dynamic law and restoration effect, providing theoretic basis for establishing scientific measures for vegetation management and utilization. The conclusion is as follows:(1) Checkerboard-like (4 x 4m) living plant sand-barriers with Salix gordejevii and Hedysarum fruticosum on shifting sand dunes can play effective role in vegetation restoration. The vegetation of the sand barrier communities would reach 24.7% within 3 years and the sand dunes would be semi-fixed. In the period from the 4th to 7th year, the coverage would reach 40%～70% and the sand dunes would be fixed. In the period from the 3rd to 7th year, the species of plant in the communities would reach 6～10 and the biomass (fresh weight) would reach 221.6～531.1kg/m~2. In the period from the 5th to 7th year, the surface litter coverage would reach 26%-49% and the stock biomass would have reached cover 105.9～340.9g/m~2.(2) In primary growth period (before 4a) of the sand barrier communities, the species is monotonous and structure simple. The checkerboard-like horizontal structure of the communities is formed by mixing vertically the Salix gordejevii and Hedysarum fruticosum introduced artificially into the communities when the sand barriers are established, there is almost not vegetation between the barriers. Along with the succession of communities and the invasion of seedlings of Hedysarum fruticosum and herbage plants in the period from the 4th to 5th year of the communities, small communities among barriers grow rapidly, forming vertical structure with multiple synusias and multiple layers, and changing from the checkerboard-like horizontal structure to the uniformly distributed horizontal structure mixed with barrier checkerboard and small communities among barriers. Then, the vegetation would be comprehensively restores.Salix gordejevii and Hedysarum fruticosum always play the leading roles in the communities. The generation and growth of small communities among barriers results in a qualitative change of the communities. Shrubbery synusia, subshrub synusia and subshrub regeneration synusia (major species) are located in different horizontal spaces in the barrier communities. There is less horizontal overlap of the coverage and biomass. Fluctuation of any party would exert significant impact to the structure, stability, function and effect of the communities.(3) The species composition and structure of the communities in the period of 4a～5a would change acutely. At the same time, large amount of standing dead biomass would appear and the coverage and biomass of Hedysarum fruticosum coverage in subshrub synusia would drop in large degree. Now, the communities are coming into the phase of decline, showing that the communities are coming into succession to the direction of species diversity and structure complication and in the unsteady development phase.(4) The soil seed band of the sand-barrier communities is also restored primarily. The number of species in the soil sand bank of the 3～7 years old communities is 3 to 6, mainly composed of one or two-annual Echinochloa crusgalli and Flos chrysanthemi. The seed density is 33～694 grains/m~2. There is a moderate comparability between soil seed bank and ground vegetation. The number of species and seed density of the soil seed bank in 7-year communities is lower than that of the semi-fixed sand dunes in Keerqin sandy land.(5) The root biomass of sand barrier communities is restored quickly. The root biomass of the 2～7-year communities reaches 49.31～230.88g/m~2. In the structure of the root biomass, specific root ratio is universally higher, 0.5394～0.8145, reflecting that the root growth is in comparative bloom and the environmental condition of the soil is comparatively comfortable. The vertical distribution of the specific roots shows a trend of shallowness at large, which is beneficial to the utilization of precipitation resource in the sand area. The plant root systems in different synusias are different in vertical and horizontal distribution spaces, well complementing each other, beneficial to utilize of soil nutrient resources effectively and keep communities stable.(6) Along with the development and succession of the sand barrier communities, the physical and chemical properties of the soil also improve gradually. The physical particle content of surface soil layer (0～5cm) has increased, the 0～50 soil bulk density increased, the total soil porosity dropped, the Non-Capillary Porosity raised and the available nitrogen, Phosphorus and organic content increased(7) Along with the development and succession of the sand barrier communities, soil is taking the trend of desiccation. In the investigation, the water content of the compared soil was 3.19%, while the water content of the 7a communities dropped to 1.9%, 40.44% lower.(8) As a result of this paper, the species that have the characteristic of good adaptability, higher survive rate and steady growth should be selected and plant them on the contour line of sand dune. When the Checkerboard-like living plant sand-barriers with Salix gordejevii and Hedysarum fruticosum to be set up, Salix gordejevi shoud be plant on the contour line of sand dune.(9) Designating scientific measures for community management according the change of community structure and the mechanism of ecological restoration is of significance for keep stability of the artificial communities and maintain sustainable development of their effect.