Northwest Degradation And Desertification Of Grassland Vegetation Restoration In The Study

At present, the grassland degradation and desertification has become an issue of China and the world, the plateau grassland area located in the northwestern Sichuan Province is no exception. In order to prevent further degradation of grassland and restore the degraded grassland, government has been actively engaged in grassland vegetation recovery, and carried out a lot of measures. This paper was based on the vegetation restoration measures in northwestern Sichuan, adopted the method of field researches combined with analysis in lab, by researching to the basic physical and chemical properties of soil and community characteristics of grassland with different vegetation recovery years, focused on the distribution characteristics, the dynamic changes and the relationship between vegetation and soil in the recovery process, and attempted to offer basis for the defending and recovering work for the grassland degradation and desertification of this area. The main results see below,(1) The soil content of soil moisture and bulk density has changed significantly. With the vegetation recovery years increased, the contents of soil moisture increased obviously, especially on the superficial soil layer. Compared with the CK1plot, soil moisture of 1a, 3a, 7a plots increased by 2.07%, 13.97%, 6.03% in the 0-20cm layer, while it increased by 6.93%, 17.17%, 10.25% in the 20-40cm soil layer; soil bulk density showed a decreased trend, 0-20cm layer of soil bulk density decreased by 0.70%, 2.82% and 1.41%, and in the 20-40cm layer, they respectively decreased by 0.69%, 17.17% and 10.25%.(2) During the process of vegetation recovery, soil chemical properties showed an increased trend, especially in the soil surface. From CK1plot to 7a plot, content of organic matter in the 0-20cm soil layer were separately 2.67 g.kg-1, 3.12 g.kg-1, 3.51 g.kg-1 and 3.22 g.kg-1, compared to CK1 plot, it increased by 16.85%, 31.46% and 20.60 %; there was a less increase in the 20-40cm soil layer. The other nutrients in the soil also changed by different degrees, including soil total nitrogen, total phosphorus, available nitrogen, available phosphorus and available potassium radiated different levels of growth trend, while the total potassium content was not obvious. Further analysis showed that the impact of vegetation recovery in the 0-20cm soil layer is greater than that in the 20-40cm soil layer.(3) The vegetation investigation reports showed that plant species were gradually increasing during the process. Community coverage and the high values of dominant species in the community were also increasing at the same time. In the CK1, 1a, 3a, and 7a plots, coverage of the community were 2%, 17%, 35% and 8%, the difference was significant. Changes of height values of the dominant species were consistent with the cover. Community with the dominance of the major species of vegetation to restore the extension of life showed three different trends. From CK1 plot to 7a plot, the aboveground biomass (fresh weight) were 86.79 kg / mu, 205.95 kg / mu, 311.46 kg / mu, and 125.80 kg / mu, compared with the CK1, that respectively increased by 137%, 259%, 45 %. Grassland production was also improved, and the Shannon-Wiener diversity index was 0.6922, 0.7166, 1.9331 and 1.3326.(4) The correlation analysis between vegetation and soil characteristics revealed that physical and chemical properties correlated with each other at a high level. The correlation index between the content of organic matter and the height of the community, the content of organic matter and biomass were respectively 0.622 **and 0.640 **, which demonstrated soil matrix interactions and vegetation promoted each other during the vegetation recovery process.(5) Changes in grassland vegetation diversity and soil nutrient content were consistent with the change of environmental conditions, which illustrated the measures to the degradation and desertification grassland promoted the improvement of soil fertility and vegetation diversity. The degradation and desertification grassland has been under effective control, the vegetation restoration measures were operative. But these changes have been only preliminary, grassland remains in a precarious state. Moreover, ecosystem restoration of the degradation and desertification grassland is a slow process, requiring a long period of restoration and monitoring, therefore, some proposal for further prevention and control grassland degradation, desertification were listed below:①Reduce grazing pressure, and promote the natural grassland restoration.②Establish the artificial fodder, ease the pressure of the grassland production.③Strengthen the selection of the drought-tolerant grass species, contribute to the artificial restoration.④Integrated management of grassland, defend rodent pest.⑤Enhance the protection awareness, strengthen the supervision.