Ecosystem Health Assessment On Grazing Land Of Leymus Chinensis Steppe

Leymus chinensis rangeland is one of the unique types of rhizomes grassland that appeared in middle-Asia. The study of its health assessment is benefit to understand the typical rangeland. Based on the ecological investigation, the dynamics of indicators related to range health were studied. The relationship among the indicators of range health under grazing intensity was also analyzed. The results showed:on family ranch scale, equity distance method was used to measure the vegetation. Based on the dominative value of vegetation, a precise grade of grazing gradients of Leymus chinensis grassland can be divided to light grazing area and moderate grazing area. As the increase of grazing pressure, plant species composition was changed. It's showed a signified decrease, while the proportion of rhizome grass was also decrease. Bunch grass occupied most the proportion of the plants and semi-shrub increased in moderate grazing area, which indicated that different plant functional group have different ways responded to grazing. Both community biomass and coverage were decreased in moderated grazing area. Photosynthesis rate of the main species decreased too. The amount of litter was also decreased. Those were the cause of poor stability of grassland system. With the increasing of grazing pressure, total soil organic matter, total potassium,total phosphate and available potassium were decreased, while soil bulk density increased. The number of soil bacteria,bacillus increased,and ray fungi,fungus decreased. The number of self nitrogen-fixing bacteria increased then decreased as the increased of grazing pressure. The indictors used for of range health assessment included 4 vegetation indictors and 3 soil indictors. There were: community productivity, total base coverage, net productivity of main species-Leymus chinensis, litter amount at May, total soil phosphate, soil organic matter, and the reciprocal of 0—20cm soil particles the diameter is greater than 0.05mm. By using the above 7 indicators, fuzzy integrative assessment method was adopted, thus, the health level of degraded grassland can be determined to health, sub-health, no-health. According to the value of range health of the degraded zone and the reference, a system can be established that is, I. Health, II. Sub-health, III. No-health, IV. Collapse. The coefficient for each level were, 1～0.76,0.75～0.51,0.50～0.26,0.25～0. This system is similar to range condition, but covered more contents. By using the quantity ecological data, combined with the fuzzy mathematics assessment method to evaluate the range health level is the first both domestic and aboard. These not only fit the gap of range health assessment in China, richen the contents of range health evaluation and provided a basic for range health indictor's framework establishment, but also giving a good guide for judge the health level of Leymus chinensis, especially in range management, which is benefit to piratical grassland strategies development, grassland animal husbandry and environment production.