1987-2008年额济纳绿洲土地覆被变化及其驱动机制

采用1987、1999年和2008年3期TM卫星数据, 对额济纳绿洲2000年黑河分水前后土地覆被变化进行了研究, 并分析了额济纳绿洲土地覆被变化的驱动因素。结果表明:(1)从不同覆盖等级的面积变化来看, 额济纳绿洲的主体是中植被覆盖区。1987-1999年额济纳绿洲的植被呈退化趋势。2000年黑河分水后至2008年, 额济纳绿洲植被退化的趋势已得到缓解。(2)从不同土地利用类型的面积变化来看, 额济纳绿洲的主体是戈壁。1987-1999年额济纳绿洲植被退化, 荒漠化趋势明显。2000年黑河分水后至2008年, 植被有所恢复, 退化趋势得到了遏制。(3)影响土地覆被变化的主要有3类因素。第一主成分与人为因素密切相关, 说明过去的十几年额济纳绿洲的土地覆被变化主要受到人类活动影响。第二主成分与地表径流量、年降水量、年均风速有较大的相关, 第三主成分与地下水埋深有较大的正相关, 表明气候因素对额济纳绿洲的土地覆被变化也有一定程度的影响。根据以上结果, 提出应对策略:(1)保证来自中上游的地表径流供给;(2)合理利用地下水资源;(3)增加技术支持, 实现宏观调控。

Land Cover Change and Its Driving Factors in the Ejin Oasis during 1987-2008

This article studied the land cover change in the Ejin Oasis before and after the water recharge of Heihe River in 2000 and the driving factors based on the TM data. The results showed that: (1) From the point of vegetation coverage levels, the principal part of the Ejin oasis is the area with middle coverage vegetation. The vegetation showed a trend of degradation from 1987 to 1999, while the trend had been restrained after the water recharge in 2000. (2) From the point of land use types, the principal part of the Ejin oasis is gobi. The vegetation showed a trend of degradation and the desertification trend is obvious from 1987 to 1999, while the vegetation recovered and the trend of degradation had been restrained after the water recharge in 2000. (3) Three kinds of driving factors influenced the land cover change. The first kind was closely related to the human factors, and it showed that the land cover change during 1987-2008 was mainly influenced by human activities. The second kind was closely related to the runoff, annual precipitation and wind speed, the third kind was closely related to the groundwater depth, and both showed that the land cover change was influenced by the climate factors to some extent. According to the results, we put forward some strategies: (1) The guarantee of runoff from the upper stream. (2) The reasonable utilization of groundwater resources. (3) The increase of the technical support and the implementation of the macro-control.