Study On Effects Of Ecological Rehabilitation Of Opencast Coal Mine In The Loess Plateau

China is the biggest country that product and consume the coal. Due to economic drivation, a lot of open-cast mining were exploited. At the same time, a mass of environmental accidents were represented. Mining is an anthropogenic activity, which causes drastic soil disturbances. Due to 2001 legal requirments in China, it is the necessity of providing comprehensive protection for the environment. In our study, We accessed the effect of ecosystem reclaimed effort through a serial of field survey and laboratory testing in the reclaimed land of the Heidaigou Opencast Coal Mine in the Loess Plateau. Through the surveys and statistical analysis on vegetation composition and soil nutrient status, the changes in the relaimed ecosystem were paid attation. The traits of the vegetation-soil ecosystem on the reclaimed system were analyzed and the benefits owing to the reclaimation were accessed.In 2006, we took a vegetation survey at the relaimed ecosystem at the reclaimed lands. The results showed that there were 115 species in the reclaimed land within the 16 years from 1991 to 2006. In the initial reclaimation stage, the annual plants played the dominant roles. By the long-term reclaimation, the perennial plants had increase substantially in plant community, and the percentage of some perennial plants may take up to almost 50%.To analyze the triggering factor that related to the development of soil functionality, a field experiment was conducted in the opencast coal mine. Results obtained from soil physicochemical properties analysis indicated that the different vegetation types affected soil forming processes obviously, especially in upper (0-20 cm) parts of the profile. The spatial pattern of reclaimed vegetation was the principal source of variability for these soil forming processes, such as the highest soil organic matter (9.23 g kg-1) and soil organic carbon (5.73 g kg-1) were observed at soil upper layer of site reclaimed with Pinus tabulaeformis, Salix matsudana, and Hippophae rhamnoides compound plant communities, which represent the most complex spatial structure. In addition, owing to a large amount of litter fall and root exudation in herbages and shrubs, soil organic matter and soil organic carbon at sites reclaimed with Leymus chinensis, Caragana sinica were significant higher than those at sites reclaimed with woody plants (p<0.05).Finally, we studied the landscape changes, landscape types and landscape features in pre and post reclaimation by means of geographical information system and the theory of landscape ecology. The six landscape types were found, which would be divided into 332 patches. Most of the natural landscapes had disappeared,and all most ecosystems were unstable. The constructions account for 23.37% of the whole area. The reclaimed woodland and pasture account for 67.90%, which occupied largest portion of the whole land.On the basis of the community composition, soil nutrient status and landscape changes, the effect of the ecological rehabilitation were evaluated. And we could anticipate that the trends of the the ecological rehabiltiation based on the study results.