Study On The Spatial-temporal Changes Of Eco-security Assessment Based On GIS And RS

The ecological security is the foundation of the national security, and theresearch this subject is one of the international frontier research. In present, there is noa successful theory and method. We take the Yulin District of shaanxi Province as aexample, the Yulin District is not only the place with interlock of farming and animalhusbandary, but also with the transition region of the desert and the loess plateau.There are multitudinous ecological environment problems in this area, such as seriousdesertification, water and soil loess and a serial of new environment problems broughtby the exploitation of mineral resources. Therefore, it is an urgency and necessity toappraise the ecology security of Yulin District syntheetically.Yulin district is located in the most Northern part of Shaanxi province, between36°57′and 39°34′N and 107°28′and 111°15′E; The climate type is temperate semi-aridcontinental monsoon climate. It covers an area of 42 986km~2. There are about 3 337000 inhabitants living in this place. The mean elevation is 1000m above mean sealevel with a maximum of 1907m in the Mt. Baiyun. The landform is compromised oftwo parts: the sandy land lies in the northern part, accounting for 48.3% of the totalarea, while the hilly and gullied region lies in the middle-south which is 51.7% of itstotal. Yulin prefecture is one of the areas of the most serious soil erosion in the worldand the Chinese government and international societies have pay greet attentation tothis area.. Soil loss in most areas of Yulin prefecture reaches 9370Mg/km~2 per year,and in some areas is even higher than 30 000Mg/km km~2 per year. This area is themain source of coarse silt of the Yellow River. The most important reason for soilerosion in Yulin prefecture is inefficient land-use and low vegetation coverage. Afterthe establishment of the People's Republic of China the desertification intensitydeclined because of rehabilitation measures. However, there is lack of knowledgeconcerning the dynamics of land use and the complex role of socio-economic policyfactors in inducing changes in land use.Taking Yulin District as an example, we use geography information system usinggeographic information system (GIS) and the remote sensing technology (RS), whichbased on the remote sensing image, DEM and partial investigations data, on-the-spot investigation and questionnaire survey, the research consist of five parts of it: (1)establishing ecology security database and based on it making a serial charts; (2)analyzing the ecology security factor dynarniclly, mainly including land use\coverchange, vegetation degree of coverage, desertification, water and soil erosion; (3)establishing system of ecology security dynamic appraisal; (4) evaluating the value ofecosystem service based on the change of land use/cover; (5) researching about theecology security sensation research.Though the systematic and scientific method, it comes to the followingsignification conclusions.(1)Using in 1988,1999,2002 three issue about MSS and TM image, we haverealized the man-machine union in RS images interpretation by the supervised andunsupervised, this method improved the of accurte of RS image, which haveprovided the foundation about supervising the ecological environment and itsdynamic monitor.(2)By analyzing the main ecology security factors, we find from 1988 to 2002,except for the rising of the pastures and construction land, we find out the rest typesother land use/cover have reduced in different. The reduction is the coverage ofvegetation is the extremely high vegetation of coverage, the high degree of coverageand the middle degree of coverage; the desertification area is gradually reducing,before 1999, the development area is bigger than reversal one. After 1999, then itturnsation to be opposite, mild and latent desertification area is reducing on largescale, but the above moderate desertification area is still expanding.(3)The overall ecological environment is worse in Yulin District, the index ofecological security is 0.502 in 1988,0.49 in 1999,0.513 in 2002 in temporal scale. inthe lowest degree in ecology security is the desert land in north, and the next is theserious erosion in south in spatial scale.(4)In 2002, the ecosystem service vale is 17109.9 billion yuan, more 4.795 billionyuan and 2.134 billion yuan than 1999 and 1988. the data has indirectly reflected thewhole ecological environment is developingin a better way.Using the method of supervised and unsupervised, the results shows this methodenhanced the accurate of images interpretation, which provided the foundationecological environment dynamic monitor.Using the remote sensing technology and many other methods such as the on-spot investigation and questionnaire survey, the article has studies the region ecologysecurity from the different aspects.Systemic and dynamic appraised of land use\cover change, soil and water erosion,desertification, vegetation and ecology security in Yulin District by GIS and RS.Base on the model of "state——pressure——response", we has established the indexof system of ecology security in Yulin District and appraised it dynamicallysimultaneously it uses the multi-methods to conduct the comparison research to thefindings.