Health diagnoses of ecosystems subject to a typical erosion environment in Zhifanggou watershed ,north-west China

摘要

Ecosystem health is the object of water and soil conservation and ecological building in loess hilly areas under erosion environment.Using principles of ecosystem health quantitative assessment and diagnosis index selection,17 factors were considered from three aspects:resource and environmental capacity,social and economic impact,and ecological services.An evaluation index system on ecosystem health was established for a small watershed under erosion conditions.Mean-square deviation was employed to determine the weight of each factor and then step-up multilayer synthesis with linear weighting function was used to build a two-level hierarchy and collection index health consultation model.The health dynamics of the ecosystem in the small watershed under erosion conditions was analyzed.Results show that the watershed ecosystem is relatively stable and has an increasing annual fluctuation (0.370 in 1985 to 0.573 in 2003) for the health index.This increasing trend indicates an adeqluately strong ability for sustainable development.At the same time,obstacles and advantages to the watershed ecosystem health were studied by introducing the concepts of obstacle degree and advantage,and path analysis method,considering the real economic optimal level as the uppermost goal.Finally,suggestions on ecological building were provided as a scientific basis for ecosystem rehabilitation in the small watershed.