Abstract: Tianzhu County,located on the northeastern end of Qilian Mountain and upriver of Shiyang River,is a part of the three plateau convergence zone(Qinghai-Tibet Plateau,Inner Mongolia Plateau,and Loess Plateau) and a fragile ecological environment.The changes of its ecosystem would impact on not only this county itself,but also the Shiyang River watershed.In addition to the pressing environmental problem,Tianzhu County is also a state-level poverty-stricken county.Therefore,the contradiction between development and environmental protection in this area is prominent.Based on Remote Sensing,Geographic Information System,and Global Position System(3S),this paper studied the land use and land cover change(LUCC) in Tianzhu County from the early 1990s to late 1990s.The results are as follows: Firstly,farmland increased at the rate of 2.34% per year with the main way of exploitation of wood-grass land and unused land,and the percentage was 80% and 17% respectively.At the same time,the phenomenon of abandoning farmland was serious,in which 74% changed to unused land.Secondly,the 91% of increased wood-grass lands was from unused land which happened mainly in the mountain areas above 4,000 meter.In conclusion,human agricultural activity disturbed the study area more intensively;the conversion of unused lands(formed in the cold climate in high latitude) in high mountains to wood-grass lands could be the response to the warming of the study area;the substantial increase in cultivated lands in study area would increase the water consumption and then aggravate the ecosystem collapse of downstream Minqin Oases.

Key words: Land use and land cover change(LUCC), Tianzhu County, 3S technology

摘要： 青藏高原东北缘的天祝县位于青藏高原、内蒙古高原和黄土高原三大高原交错带,生态环境脆弱。因其处于石羊河上游地区,所以其环境变化还可能影响整个石羊河流域。此外,天祝县还是个国家级贫困县,经济发展与生态保护的矛盾也比较突出。文章基于3S技术,研究了20世纪90年代土地利用/覆盖变化格局。结果表明:耕地以每年2.34%的速率递增,主要增长方式是开发林草地和未利用土地,同时耕地摞荒现象比较严重,74%的耕地减少方向是转为未利用土地;91%的新增林草地来自未利用地,而且,大部分以分散形式发生在4000 m以上的高山上部。因此,人类农耕活动对该区域的扰动比较剧烈;高山上部未利用地向林草地的转化可能是对研究区域气候变暖的响应;研究区域持续的耕地增长带来的水消耗增加可能会加剧下游民勤绿洲的生态环境恶化。

关键词: 土地利用/土地覆盖变化, 天祝县, 3S技术