| Ecological environment is not only the basic needs for human survival and development, butalso the material foundation of economic and social development. With the development of societyand economy，the eco-environment problem has increased dramatically. Nowadays, its vulnerabilityis one of the top concerns in global environmental change and sustainable development project, andhas attracted many scholars’ attentions.Yanhe Basin is located in the central Loess Plateau of the northern Shaanxi province, which is atypical gully region of Loess Hilly Region. The complex conditions there, combination of regionalnatural, cultural, economic, and geographical, as well as the detrimental impact of natural disastersand environmental destructive activities, made the basin suffers from fragile ecological environment,serious soil erosion, and fragile ecological environment. Evaluating the ecological vulnerability ofYanhe Basin and grasping the ecological environment and spatial pattern has a great significance toecological construction and the sustainable development.Take the Yanhe Basin of Loess hilly region as study area, based on the RS and GIS technologiesand the method of spatial principal component analysis (SPCA), the integrated assessment ofeco-environment vulnerability are studied on two scales from regional to watershed, systematicanalysis of the ecological vulnerability spatial differentiation of Yan Basin. And further discuss thevulnerability variation characteristics on a regional scale, preliminary study on its driven mechanism.The main conclusions are as follows:(1) Ecological environment vulnerability of Yanhe Basin was decreased as a whole, but still in afragile state, mainly at moderate level. Slight and light fragile areas are mainly distributed in thesoutheast Baota District and Yanchang county, which is the best ecological environment quality areain the Yanhe Basin; the moderate fragile areas are mainly located in the southeast of Ansai County,Yanchuan County and Baota District; severe and extremely vulnerable area accounts for about11%of the whole area, mainly in Jingbian County, northwest of Zhidan County, northwest of AnsaiCounty and the part region of Zichang county. From the point of view of the overall pattern of spatialdistribution, the study area’s ecological fragility gradually decreased from northwest to southeast.(2) Eco-environment vulnerability assessment of typical small watersheds in differentvegetation zones show that the eco-environmental vulnerability in steppe zone was at heavy level,forest steppe zone at medial level and forest zone at light level, the ecological fragility in typical small watershed internal of the same vegetation zone are similar.(3) The vulnerability grade of typical small watershed in different vegetation zones all showed acertain regularity with the slope changing. Slight vulnerability was mainly distributed within3degree, and then appeared wavy changing trend of "decreasing-increasing–decreasing ", the othergrades increased first and then decreased with slope increasing. And all reached the maximumbetween15degree and35degree. At the same time, special geomorphic features and erosionenvironment, making the most ecological vulnerable areas located in gully slope.(4) The dynamic evaluation of the time series shows that, during the period1990-2000, theecological environment of Yanhe Basin showed downtrend at whole; and then gradually improvedand stabilized between2000and2010. In the space level, the farther away from the city center, thelower degree of ecological vulnerability; and farther from the river, the higher degree of ecologicalvulnerability.(5) Adopt the mathod of space principal component analysis to study the driving force of theecological vulnerability in Yanhe Basin, initially determines four major driving factors areinfluencing eco-ecological vulnerability in the region, that is terrain condition, vegetation cover, landuse types and meteorological factors. |
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