Research On Land Use/Cover Change And It's Environment Impact In Naidong County, Tibet

Qinghai-Tibet Plateau is regarded as the main environmentally problematical region relating developemnet of China. The dynamic change of land use structure in "Yaluzangbu River, Lasa River and Nian Chu River" area has significant influence on society, economy, ecological system and some other aspects.Land degradation is impacted by land use ,which is a key node in the human environment relationship. In this context, the present study analyses the land use/land cover change and its local environment impact, As a case study, following aspects have been analyzed in Naidong County.1.Research on land use change. Landsat remote sensing images are interpreted to obtain land use types change and their distribution changes in Naidong County. From 1988 to 2000, land use type change in case study area shows that land use change in Naidong County happened mainly near the valley. Much natural vegetation was replaced by artificial forests. These changes are directly related to human activities aiming to improve regional environment, such as tree planting, grassland restoration during the implementation of the integrated agricultural development project at that time.The most remarkable increase in area is forest as the forestland increased 1323. 93 hm~2 during 12 years. Rangeland and water body in study area had rapadiliy decreased and most of them changed into forestland. Hrticultural land with a high rate of change, but the area increase is not very remarkable (113. 32 hm~2) . The area of cultivated land and unused land had disapparently decreased. The land use degree of study area is increasing gradually, the order degree of land use system is decreased as the increase of information entropy values.2.Assessment of land cover change. Land cover change can be considered as considerd as the result of land use. Bare soil and rock are important land cover types in Tibet area besides the vegetation. Bare soil links with soil erosion and exposure ratio of rock denotes the degree of recky desertification. General approach such as "Land-use/land-cover classification" or "vegetation index" cannot estimate quantitatively the vegetation, bare soil and naked rock at the same time. The thesis introduces the linear spectral un-mixing technology so as to detect the ratio of vegetation, bare soil and naked rock in every pixel. It can be learned, through this approach, that the proportion of bare soil reduced evidently while rock and vegetation enhanced from contrasting the unmixed results of the remote sensing image of 1988 and 2000 respectively. It is proved that vegetation cover had been recovered partly while rocky desertification expanded rapidly.3.A systemic analysis on the process of regional land use/cover change and their local environment impacts. This thesis analyzed changes in land use and ecosystem service values using the ecosystem service value coefficients put forward by Costanza et al. In addition, coefficients of sensitivity were introduced to test the rationality of ecological value coefficients. Results show that from 1988 to 2000, area of rangeland, water bodies decreased and forestland increased. Due to comparatively big valuation coefficients(VC) of water bodies, the increasement in forestland could not offset the total decrement in regional ecosystem service values because of decrease in area of water bodies. The total ecosystem service values of the study area reduced dramatically. This thesis aimed to provide decision support for sustainable use of resources and protection of eco-environment by assessing land use change and its consequent changes in ecosystem service values of Naidong County.Under the background of Chinese westerm region development and ecotone's ecological rehabilitation the studies in this thesis have important significances. They offer scientific bases for supporting the approaches that can improve and resume the regional environment with the optimum management of land use. Some suggestions are offered for ecological rehabilitation based on the systemic analysis. These all build a foundation to develop and use the land resource reasonably and sustainably. Therefore guarantee the sustainable development of our national economy.