Dynamic Of Ecological Environment Of Fenced Grassland And Its Management In Yanchi County

Grazing prohibition and fencing is one of the most important ecological protection projects in our country, especially in arid and semi-arid regions. Degeneration and desertification of grassland can be contained; habitat and conditions of the rest for grass can be offered by implementing Returning farmland to forest and fencing policy. It can promote the rapid recovery of grassland vegetation to achieve sustainable use of grassland resources and the virtuous cycle of natural ecological system.The present study takes Yanchi County for example, where is in Ningxia in one of the agricultural-pastoral regions suffering from the most severe desertification in northern China. It is based on the National Desertification Localization Monitoring Project. From the perspective of ecology and use, the succession of vegetation community, the change of soil texture features and the health of the grass have been analyzed by combining sample plot survey with remote sensing. Trying to find the best recovery measures of desertification of grassland vegetation, explore the grassland ecological management model, to solve the conflicts between ecological protection and economic production, and provide theoretical basis for the desertification of grassland vegetation restoration and pasture management.The main achievements are as follows:(1) Herbs were dominant in study area, and there were most perennial herb majority and least shrubs, half shrubs. Leguminous and Compositae were the most extensively distributed dominate, followed by Gramineae, Chenopodiaceae. The vegetation in study area was classified into seven types at level four by TWINSPAN classification.(2) Research on vegetation succession of different sandy land on the north suggests that the general positive succession is annual herb short-lived pioneer plantsâ†'annual or biennial herbsâ†'perennial herbsâ†'Half shrubs, perennial shrub. Farmland to forest land, natural grassland and plowing area is in the midst of the positive succession stage of annual and perennial herbs as the main dominant species; New enclosure area and half enclosure area are in the midst of the positive succession stage of half shrubs, shrub and perennial herb as the main dominant species; Old enclosure area is in the midst of the reverse succession tendency of perennial herbaceous plants as the dominant species. In the process of positive succession of vegetation community, niche breadths are reaching the homogenization.(3) The research on vegetation characteristics of the plowing area shows that plowing can increase biodiversity and improve community evenness, but its effect is not significant. Numerical fluctuation of vegetation coverage and biomass of new plowing area is very big and have not obvious improvement. So for the current study, ribbon-like plowing is not a very good means for pasture use in Yanchi.(4) The soil nutrient status is very poor, content of total nitrogen, available nitrogen, total phosphorus, available phosphorus, total potassium, available potassium and organic matter is very low. The physical and chemical properties of soil surface are mainly affected by grazing disturbance. Soil moisture content of different depth in enclosure area is the largest. Available nutrients content are affected by disturbance gradient obviously, the greater the interference, the lower the nutrient content.(5) Divide healthy level of grassland by many influential factors. Master grassland accounts for 0.39% of the total grassland area, medium accounted for 60.18%, inferior accounted for 39.43%. Unit ecosystem service value of master grassland was 6286.98RMB/hm2-a, medium is 3627.41RMB/hm2-a, inferior is 1375.79RMB/hm2-a. The total ecosystem service value of grassland of Yanchi was 1375.79×106RMB in 2014.(6) The effects of enclosure measures on vegetation restoration was obvious. It can protect the vegetation from interference and provide good conditions. Community biodiversity were increased, soil nutrient status was improved, so as to promote community recovery reached a relatively stable state. From figures of vegetation cover can also be seen, vegetation coverage of 2003 and 2004 increased significantly after 2002, in which year grazing prohibition policy began to be implemented. Long term enclosure is not conducive to vegetation recovery. Over the years of fencing, the biological crust began to formed and more and more. Biological crust not only competed with plant for water and fertilizer, but also affected the moisture infiltration directly. The best period of completely fencing is about 8 years. Considering the vulnerability of ecological system of Yanchi, it is recommended that the management of grassland were classified. Grazing prohibition policy can be continue executed on inferior grassland, seasonal grazing or rotational grazing can be used on medium and master grassland. The compromise of economic production and ecological protection is 45% of the aboveground biomass.(7) Under grazing prohibition policy, the best way to inhibit grazing is combining to strengthen supervision and punishment with improving long-term profit of herdsman. When long-term profit is equal to the short-term benefits of grazing without permission, even if the government does not supervise the nomads nor grazing. Combining rotational grazing, seasonal grazing with the subsidy to improve herdsmen income is the best way.