The Study On The Ecological Vulnerability Based On Remote Sensing In Yulin Region

China is one of country with the largest ecological area, most ecological types, and obvious ecological vulnerability in the world. Argo-pastoral transitional zone is typical ecological vulnerable zone, with the biggest area, the longest spatial span and special agro-pastoral transitional character in China, and is also an important ecological shelter for North China. Yulin region in Shaanxi province is a typical vulnerable area in agro-pastoral transitional zone. In our study, Yulin region was taken as study area. We combined the methods of Remote Sensing (RS) and Geographic Information System, made several disciplines as theoretical guidance, such as landscape ecology, climatology, statistics, and son on, further selected some ecological factors, for example, climate factors, land cover, multi-temporal remote sensing data, economy, pressure, and quantitatively analyzed spatial-temporal variation of ecological environment and the status of its’ vulnerability. By using of trend analysis, abrupt analysis, wavelet analysis, landscape indexes, the spatial and temporal characteristic of climate factors, land cover and landscape, and vegetation fractional cover were quantitatively analyzed. The evaluation index system of ecological vulnerability was built based on analysis above. The ecological vulnerability of Yulin region was quantitatively evaluated by using of the information integration model. With the study, it can be provide the theoretical foundation and scientific basis for arid and semi-arid region in China. Through the above study, some conclusions were acquired as following:(1) During1970-2010, Climate in Yulin region gradually turn warm, precipitation fluctuate very much, and solar radiation descend obviously. The ecological vulnerability resulted form climate change gradually ascend. In past40years, the annual temperature indicators showed obvious fluctuation trend, and increased with the range of1.4-1.8℃, which was higher than the national average level. The increasing of temperature in spring and winter had much contribution to the ascend of temperature in the study region. The indexes of temperature in spring, autumn and winter become active. Annual precipitation fluctuates very much and the tendency was not obvious. Precipitation in summer and winter decreased, while increased slightly in spring. The frequency of periodic changes of precipitation in spring ascends, and descends in other three seasons. Solar radiation showed a down trend, and periodic changes of them were not obvious. Thus, ecological vulnerability caused by climate change increased in Yulin region. (2) During1985-2010, the spatial difference of ecological vulnerability resulted by the change of land cover and landscape ascend.under the development of returning farmland to woodland project, woodland and water body gradually increased, farmland and grassland decreased in the southeastern part of Yulin region. Unused land and settlement keep a sustained growth trend, and this phenomenon mainly distributed in the northwestern part of the region. Land degradation and urbanization also intensified in this part. Thus, ecological vulnerability caused by land cover change increased in the northwestern part, and decreased in the southeastern part of Yulin region. The landscape changes in1995in Yulin region marked as a turning point. Before1995, the degree of landscape fragmentation reduced gradually. The average area and connectivity of patch increased gradually. Spatial heterogeneity and the complexity of landscape structure also reduced. After1995, the landscape pattern present opposite tendency. Compared with2000, the landscape pattern in2010was relatively complex, with poor connectivity, and obvious fragmentation. Thus, the ecological vulnerability caused by landscape change was relatively obvious.(3) The ecological vulnerability caused by vegetation cover increased in the northwestern part and decreased in the southwestern part in Yulin region. From temporal scale, vegetation fractional cover presented a fluctuant increasing trend in Yulin region during2000-2011. The area of extreme coverage (Pv≥0.70), high coverage (0.7>Pv≥0.50) and medium coverage (0.50>Pv≥0.30) increased obviously. The other levels of coverage area showed difference degree of reduction. From spatial scale, vegetation cover gradually decreased from southeast to northwest during2000-2011. In recent12years, vegetation cover in the southeast of Yulin region increased obviously, but increased insignificantly, and degradation of vegetation still exists in the northwest of the region.(4) From2000to2010, the temporal-spatial distribution of ecological vulnerability was much difference in Yulin region. Ecological vulnerability gradually became vulnerable in the northwestern part and stable in the southeastern part. Compared to2000, ecological vulnerability in six counties in the southeastern part of the region decreased, basically unchanged in two counties in the central region, and increased in fourth counties on the edge of Mu Us land in the northwestern part. In2000, the climate in Yulin region was very arid, which lead that vegetation fractional cover was very low. Farmland, grassland and unuseland took up most area of Yulin region. The overall level of economic development in the region didn’t show much different in space. Thus, ecological environment in Yulin region was very vulnerable, and didn’t present much difference in space scale. In2010, the effect of human factors was much obvious in space scale. Under the driven of eco-environment protection measures, the area of woodland increased in the southeastern part of the region. Vegetation cover improved obviously. Climate was more humid than that in the northwestern part. The development of economic was relatively slow. The negative effect of human activity was much slight. Thus, the ecological vulnerability was low, and have an trend of improvement in the southeastern part. But in the northwestern part, vegetation cover increased insignificantly, unused land increased;the economic develop quickly, the urbanization gradually accelerated. The effects on ecological environment from human activity exceed the change speed of other driving factors of ecological vulnerability. Thus, ecological vulnerability in the northwest of Yulin region increased.The complex geographical conditions and socio-economic conditions determine the sensitivity and vulnerability of ecological environment in Yulin region, resulting in a temporal-spatial difference of ecological vulnerability. Through quantitative evaluation and analysis of driving factors, the degree of ecological vulnerability and its’temporal-spatial distribution, it can provide foundation and basis for decision making for the restoration and improvement of regional ecological environment, and provide technical support for survey and monitoring of ecological environment in the agro-pastoral transitional zone in North China. The innovation in our study can be seen as follows:we quantitatively analyzed the characteristics of spatial-temporal change of climate, land cover and landscape, and vegetation cover, revealed the characteristics of spatial-temporal change of driving factors and characterization of ecological vulnerability, and combined with other driving factors of ecological vulnerability to set up the assessment indexes system of ecological vulnerability. We also used the same processing method and the scalable information integration model to evaluate the spatial-temporal distribution of ecological vulnerability, provided a starting point and ideas for different disciplines to study on ecological environment, such as Remote Sensing, Geographic Information System,Landscape Ecology, and so on, and realized comprehensive application from different disciplines on the study of ecological vulnerability.