The Utility Study On The Ecological Restoration Of Degraded Grassland In Northwestern Sichuan During Grazing-prohibited

There is rich grassland resource in China, but it began to depredate because of excessive and unreasonable use from the 1950s to 1960s. In order to prevent further degradation of the grassland and carry through the restoration of degraded grassland, the "Retirement and Environment Project" was put forward in 2002 and formally launched in the west in 2003. The implement of the "Retirement and Environment Project" brought the eco-efficiency, social and economic benefits studies. This paper penetrated into studying the grassland regions at the "Retirement and Environment Project" in Northwest of Sichuan, and provided a theoretical basis and guidance to the "Retirement and Environment Project". The research indicated that:1 The species richness at "Retirement and Environment Project" region showed the trends of a single peak; the Shannon-wiener diversity index and the Pielou eveness index showed the same rule, both were decreased as well as the grazing-prohibited year increased. All of these further confirmed the accuracy of this study.2 The research on the life-functional group of grassland community showed that different changes and trends existed in the proportion of the life-functional group of grassland community after grazing-prohibited, the larger promotion changes existed as Cyperaceae plants, Poisonous plants and Forb plant, the proportion of Gramineae and legumes plant were small. The promotion of Cyperaceae plants increased from 21.83% at the first grazing-prohibited year to 55.13% at the fourth grazing-prohibited year; the promotion of Poisonous plants decreased from 21.83 at the first grazing-prohibited year to 49.37% at the fourth grazing-prohibited year; and the promotion of Forb plant decreased from 27.53% at the first grazing-prohibited year to 11.14% at the fourth grazing-prohibited year. The changes of the proportion of life-functional group of grassland community indicated that the promotion of the edibility grass increased, and the community structure gradually optimized.3 The research on the spatial distribution of existing showed that grassland communities in "Retirement and Environment Project" region was bigger than the no grazing-prohibited region; the above grassland communities promotion of the 0-5cm layer decreased, but the 15-30cm and the above 30cm layer increased as the grazing-prohibited year increased; the underground root biomass proportion of the 0-5cm layer decreased from 91.26% at the first grazing-prohibited year to 73.56% at the fourth grazing-prohibited year; but the underground root biomass proportions of the 5-10 cm and 10-15 cm layers were increased from 6% and 2.47% at the first grazing-prohibited year to 21%and 5.64% at the fourth grazing-prohibited year respective. So the grass plants promoted to the ground and upper ground floor developed as the grazing-prohibited years increased.4 The research on the soil moisture showed that the soil moisture in the grazing-prohibited region was higher than the no grazing-prohibited region except the second grazing-prohibited year at sloping field; the soil moisture was lower than the no grazing-prohibited region at flat after grazing-prohibited for one or two years, but at the tired and fourth grazing-prohibited years, the results were reversed. All the results showed that the soil moisture not only affected by the grassland community, but also signify affected by the agrotype, physiognomy and so on, the soil moisture as a factor of the degraded grassland restoration affected by the outside factors obviously.5 There was small relative between the number of the edaphon and grazing-prohibited years in "Retirement and Environment Project" region, because the number of edaphon affected by many factors, on the other hand the edaphon couldn't be completely isolated from the soil as the limit of the separation conditions and methods, so the number of the edaphon couldn't be a accuracy factor measured the degraded grassland restoration.6 The number of the germination seed in the grazing-prohibited region was more than the number of no grazing-prohibited region except the third grazing-prohibited year, it indicated that "Retirement and Environment Project" had important effects on the restoration of soil seed bank, and the soil seed bank could be a measure of the degraded grassland restoration factor, but if use the method of combining germination and physical separation to separate and identify the soil seed, the accuracy would be higher.7 Results indicated that the species richness, species diversity, life-functional group proportion, spatial distribution of the standing crop, soil seed banks and other indicators of the grassland community significant related to grazing-prohibited years, also can be used as the evaluations of the restoration of degraded grassland ecosystem; but the soil moisture and edaphon number of the grassland changed larger as the external conditions and the test method, so these had little accuracy as the indicators of the restoration of degraded grassland.