Study On Land-Use And Land-Cover Change Of Tianzhu County In Gansu Province

Tianzhu County, located on east end of Qilian Mountain and the upriver of Shiyang River, is a part of three plateau convergence zone (Qinghai-Tibet plateau, Inner Mongolia plateau and Loess plateau), with fragile ecological environment. Its change of ecosystem affects on not only this county itself, but also on Shiyang River watershed. In addition to the pressing environmental problem, Tianzhu County is also a state-level poverty-stricken county, which rises the difficulty of solving environmental problem. So, the contradiction between development and environment in this area is prominent.Based on Remote Sensing, Geographic Information System & Global Position System(3S), this thesis researches Land Use and Land Cover Change(LUCC) in Tianzhu County from the early 1990s to late 1990s, and forecasts the trend of LUCC in recent years by Markov model, then calculated the profit and loss of ecological value from LUCC.The result data indicates:1. Monitoring regional land use and land cover change by 3S technology is feasible. It can provide not only the number of change but also the information about where the change happens, the sources and the whereabouts of the change, which makes the possibility to depth analysis.2. Land use pattern in Tianzhu county is dominant by wood-grassland with the percentage above 60%.3. The most important features of land use change in study area during 1990s, 20cn are:(1)Farmland grew at the rate of 2.34% per year. Its main way of growth is developing wood-grassland and unused land, and the percentages are 79.58% & 17%. At the same time, the phenomenon of abandoning farmland is some serious, in which 73.74% decrease of farmland changed to unused land.(2)In the growth of wood-grassland, 91.04% is from unused land. From the view of spatial distribution, 81.03% of the growth happened around mountains which altitude is over 3,000 meters, for example, Maya Mountain, Leigong Mountain, Hua Mountain, Daxueshan Mountain as well as Maomao Mountain, which shows ice line in study area rising during the period of study.4. It's forecasted by Markov model that the trend of LUCC is farmland growing, unused land and wood-grassland reducing in the future if the policy keep in steady state.5. Estimate data show that the ecological value of wood & grass land and water are decreased, while the gross ecological value is increased. The mean reasons are: the first, some farm land that be developed by unused land raise the gross ecology value; the second, the deference classification of grass land is not identified.