| Based on the historical statistics data (hydrographical, meteorologic and vegetational) and the field survey data, regarding plant population as the indicator of the regional ecoenvironmental degradation, reflect the effect of the climate change and anthropogenetic activity on the eco-engvironment degradation in the northeastern margin of the Qinghai-Tibetan Plateau. Water resource changes (Changes of Surface Water System, Changes of Water resource amount) and vegetation variation (Alpine meadow degradation, Changes of grassland and forest ecosystem) were studied in this paper. At the same time, applying the ERDAS, MAPINFO, ARCINFO and GIS software, interprete the satellite images of 1982 and 2001 and test the variation amount of wetland.According to the interpretation to the satellite images of 1980, 1990 and 2005 with reference to the historical maps and GPS positioning survey data on-the-spot. Based on the Post-Classification Comparison Change Detection, transfer matrixes of LUCC from 1980 to 1990 and 1990 to 2005 were made and the features of LUCC were analyzed in the northeastern margin of the Qinghai-Tibetan Plateau.In order to evaluate the fragile index of the northeastern margin of the Qinghai-Tibetan Plateau, the intergrative and classified evaluation method was adopted, and index system and index weight were constructed in this paper.Using(?)obtained the ecoenvironmental fragileindex and evauated it.(1)The regional hydrology and ecosystems of the northeastern margin of the Qinghai-Tibetan Plateau have changed over the past 40 years driven by intense human activity and regional climate changes. Annual mean air temperature has increased in the region. Streamflow from the northeastern margin of the Qinghai-Tibetan Plateau has decreased significantly. Overall, a number of Alpine step meadows and Alpine frigid meadows have seriously degraded. Degeneration of vegetation and grassland led to desertification and frequently induced dust storms. With the continuous increase in cultivated land area, grassland area in the region has dropped significantly since the 1960s. At present, degraded grassland occupies about 83% of total usable grassland area. As the number of livestock increased, range condition deteriorated and the carrying capacity was reduced. The forest area in the northeastern margin of the Qinghai-Tibetan Plateau has decreased by 20%, and the local ecosystem has become very fragile.(2)The amount of water resource in the northeastern margin of the Qinghai-Tibetan Plateau has shown a steadily downward trend since 1950s. By analyzing hydrological data (1956 - 2004) of the study areas, the results showed that the multi-year variation of water resource of 4 catchment regions had similar patterns from 1956 to 2004. The maximum occurred at the middle and end of 1960s in all catchment regions, and declined thereafter.(3)From the 1970s to the 1980s the areas of Alpine step meadows, Alpine frigid meadows and swamp meadows in the northeastern margin of the Qinghai-Tibetan Plateau decreased by 2.26, 3.73 and 24.53% respectively, whereas it decreased 6.64, 24.21 and 34.45%, respectively, from 1980s to 1990s.(4)With the continuous increase in cultivated land area and number of livestock, the area of degraded grasslands in the northeastern margin of the Qinghai-Tibetan Plateau had increased significantly since the 1950s. In this region, there was about 2,361,000 ha of natural rangeland, and degraded grassland occupied about 83.20% of total usable grassland area, in which severe and moderate degraded grassland area was 814,000 ha and 1,370,000 ha, respectively; desertified grassland was 53,300 ha, and salt-affected grassland was 5,500 ha. The amount of quality forage declined from 70% to 45%. The areas invaded by noxious weeds had increased from 30% to 55% since 1980s.(5)The area of forest land in the northeastern margin of the Qinghai-Tibetan Plateau has dropped significantly since the 1950s. At the end of 1998, the northeastern margin of the Qinghai-Tibetan Plateau had lost 23,000 ha forest area and 26,270,000 m~3 wood accumulation, representing 35.11% and 32.59% reduction, respectively.(6)Average air temperature showed a fairly rapid increase since 1990s in the northeastern margin of the Qinghai-Tibetan Plateau. The decade of mean air temperature departure was - 0.4 - - 0.3, - 0.3 - - 0.1, - 0.1 - 0 and 0.2 - 0.5℃, for the periods of 1960-1970, 1970-1980, 1980-1990, respectively.(7)Over the past 4 decades the annual precipitation in the headwater area showed no noticeable changes or it remained stable.(8)The increased temperature has caused the degradation of permafrost. In the northeastern margin of the Qinghai-Tibetan Plateau, the lake water area in the region has decreased and water areas of most lakes and rivers were reduced because of permafrost degradation. The lake water area shrank by 0.54% from 1970s to 1980s, and by 9.25% from 1980s to 1990s.(9)At present, the grassland was overstocked and overgrazed, the grassland available per head of sheep ranged from 0.45 to 0.50 ha. Overgrazing resulted in degradation of the grassland ecosystem.(10)Based on the matrix of LUCC, there were significant change of LUCC from 1990 to 2005 in the northeastern margin of the Qinghai-Tibetan Plateau.(11)Environment fragile represented as intensive fragility with index of 0.59 from 1987 to 2005 in the northeastern margin of the Qinghai-Tibetan Plateau.(12)Analyzing the relationship between fragile index of ecoenvironment and fragile factors and knowing the relative sequence between all factors and fragile eco-environmental index is: productive forces of grassland > precipitation > percentage of forest cover > cumulative temperature (≥10℃) > rural per capita net income > the ratio of the income of livestock to the gross income of agriculture > aridity > the ratio of catastrophic area to the calamitious area > the relativity variation rate of precipitation to 1986's > per capita income of industry > the ratio of capita income of enterprises in townships and towns to capita gross dommestric product > per possession of grain > the ratio of non-farm population to total population > the natural growth rate of population > Engel coefficient > the ratio of non-illiteracy population to illiteracy population.(13)Analyzing the relative contribution of natural fragile factor, economic fragile factor and society fragile, obtain each fragile factor drive proportion is 64.36%, 28.57% and 6.09%. Showing the effect of natural fragile factor on the environment was higher than society and economic fragile factor.To avoid further deterioration of the environment and ecosystems, it is important to establish and implement ecosystem protection countermeasure. Some effective measures are essential in this respect, including technical and political considerations.
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