Ecological and environmental evaluation for water and soil loss comprehensive harness in Loess hilly region

Hierarchy, complexity and polytropy of eco-environment determine the difficulty in accessing its quality. It is a key issue that many scholars concern for a long time in establishing a set of index system and evaluation method, which is reasonable, scientific and representative in solving the same kind of problem. Methods of Grey relation degree, comprehensive evaluation and DPSIR-mDSS model (driving force, pressure, state, impact, response framework-multiple decision support system) were adopted to compare their difference in accessing eco-environmental effects. Meanwhile, demonstration area of soil conservation and eco-environment construction in Yan'an was taken as a study object to access environmental effects of ecological restoration of water and soil loss comprehensive harness from 1999 to 2009. The results showed that complicated relationship between human social and economic behavior and environmental system could be simplified to "one to one" causal chain by DPSIR model in constructing index system for accessing environmental effect of ecological restoration of water and soil loss comprehensive harness, accessing process could be decomposed and simplified. Also, the evaluation results of DPSIR-mDSS model was consistent with the actual situation of ecological restoration effects of study area, and would be better explained the variation of ecological restoration effects of water and soil loss comprehensive harness with time, which also provide a new method for ecological restoration effects assessment. In general, the eco-environmental status improved greatly due to the implement of "grain for green" project. However, more attention should be paid to problems in the future, such as pressure on cropland and ecological water storage deficit.