Study On Ecosystem Health Assessment In Lanlingxi Small Watershed

The ecosystem health is closely related with social economics, human activity and eco-environment. In recent years, with the deterioration of watershed environment increasingly, It is becoming one of the study focuses that how to assess the watershed ecosystem health in water conservancy science, environmental science, ecology and other fields.Taking the Lanlingxi small watershed as the study object, basing on pressure-state-response model built by Organization for Economic Co-operation and Development (OECD), and adapting some remote sensing images, DEM, and other statistical investment data, using 3S technology, this paper established a spatial database which contain 12 evaluation index(fertilizer employing intensity, pesticide employing intensity, population density, human disturbance index, NDVI, importance value of high quality vegetation, landscape fragmentation, ecological elasticity, material production, soil erosion intensity,reclaimed index of land, per capita net income) based on 100 m×100 m grid cell. Then, the paper obtained the ecosystem heath assessment results of Lanlingxi small watershed in 2002 and 2007 by using relative comprehensive evaluation method, and further analyzed the spatial and temporal distribution rule of the watershed ecosystem heath and its connection with pressure. The results indicate as follows:1. The average of comprehensive evaluation index of the small watershed ecosystem heath increased from 0.531 in 2002 to 0.781 in 2007. The index varied from 0.177 to 0.788 in 2002 which shows statistically normal distribution, while 0.325 to 1 in 2007 which shows statistically skewed positively distribution.2. In the spatial distribution, the watershed ecosystem heath shows some Distribution Characteristics of Geographical elements. In horizontal direction, it is better in the southwest than in the northeast and the east. While in vertical direction, it is better with the altitude increasing.3. Changes in terms of time, the watershed ecosystem heath significantly improved in the past 5 years from 2002 to 2007. The grid area which be improved accounts for 94.444% of whole area, in which 63.270% be significantly improved, and 19.778% be obviously improved; While 2.024% deteriorated, in which 0.034% significantly deteriorated; and 3.531% has no change.4. The statistical results of pressure indicate that, In 2007,the areas in which the pressure is more than they can bear are among 3.711% in 2002 that has reduced to 0%; And the areas beyond the generally scope has dropped from 6.544% down to 0.135%. but the areas in which the pressure is at normal range has raised to 90.609% from 59.137%. Generally speaking, the pressure on the small watershed ecosystem obviously reduced, the regional ecological environment has been improved significantly. In addition, derived from statistical results of the pressure distribution in 2002 and 2007, we can take that the pressure has a negative relationship with the small watershed ecosystem heath, and the areas in which on the high pressure is decreasing, but the areas on pressure are mostly in the northeast,central and southeast where the ecological environment are bad.