Landscape Pattern Change And Ecological Security Evaluation Of The Tibet Autonomous Region

Based on two periods of land use data in Tibet in 1985 and 2000(scale 1:100,000) and combined with field investigation and ARC/GIS software support, the database of landscape classes was established. The landscape indexes were calculated by Fragstats. The landscape pattern change driver was analyzed by the canonical correlation analysis of SPSS. Finally, assessment system was built, and the ecological security of Tibet landscape was evaluated by ARC/GIS. The conclusions were as following:(1) Compared to 1985, the area of each landscape class altered notably in 2000. Unused land, construction and communication land, shrub and woodland increased while agriculture land, forest, grassland, drainage basin, lake and ice land decreased. 80.2 % of the grassland transferred into unused land, which was the most in transfer-out. The construction land was the most in transfer-in, 81.6% coming from agriculture land, grassland and drainage basin. Unused land increased by 70215.25 km~2, most coming from grassland, forest and drainage basin.(2) From 1985 to 2000, the landscape pattern of the Tibet changed noticeably, the patch amount, diversity, and equality increased, while the dominance, shape index, connectivity and fractal dimension decreased. The landscape pattern developed towards more fragmented, diversified and simplified. By comparing and analysing landscape index of seven regions in Tibet, great difference existed among them, landscape heterogeneity and landscape connectivity of seven regions was increased between 1985 and 2000.(3) The initially transformation matrix of landscape elements was built by applying Arc/View3.2 and Excel. The Markov forecasting showed that under the same disturbancesbetween 1985 and 2000, unused land, build-up land and shrub land area increased, however, grassland, water, agriculture land and other types decreased year by year. The landscape pattern changes driver analysis showed that Tibet landscape dynamics is constrained by height, rainfall, temperature and other natural factors, especially the increase in population, livestock production increased, residential building sites increased, etc. played a key role.(4) By establishing an evaluation system and using AHP to determine the evaluation factors weights, the valuation model of ecological security was built in this paper and the overlay function of raster-GIS was used to make a result map. Tibet regional landscape security synthesis evaluation results: in 2,000 compared with the 1980s the ecological security index of Tibet region decreased. Based on the of the result above, the author brings forward the protective measure and project of respecting the natural ecology process, arranging human activities intention and ways rationally, which can offer academic gist for landscape ecological security and landscape pattern optimization in Tibet region.