青海湖流域土地利用/覆被变化研究

研究青海湖流域的土地利用/覆被变化,对识别流域人类活动特征和分析区域生态环境演化规律及其成因具有重要意义。文章以1977~2004年4期遥感影像数据为基础,采用土地利用转移矩阵、动态度、利用程度等方法,研究了青海湖流域1977年以来的土地利用变化特征及其空间分异规律。研究结果表明:①近年来流域内生态用地数量逐渐减少,其中水域面积净减少292.70km²;②对草地的开垦占用是流域增加耕地的主要来源,1977~2004年因湖泊水位下降而增加的沙地面积为103.22km²;③1977年以来,流域内除2000~2004年水域面积减少速率显著上升达0.71％外,其他主要类型土地面积变化速率不断减缓;④流域内沙地主要分布在海晏县(70％以上),90％的林地和95％以上的耕地均分布在刚察、共和两县,各县土地利用结构变化特征存在差异;⑤土地利用程度综合指数平均值为186.47,明显低于其他地区,说明人类活动对流域土地利用变化影响较小,区域生态环境问题的研究应当更加注重自然因素的驱动作用。

Land Use/Cover Change in the Qinghai Lake Watershed

In the recent years, Qinghai Lake has experienced severe declines in water level and its watershed is in an advanced state of ecological degradation, which resulted from both natural (climatic) and anthropogenic factors. However, information concerning human activities (e.g., land use/cover change) is scarce, therefore, it is necessary to know land use change and its effects on ecological degradation in the lake watershed. This would help us to have a better understanding of the effect of human activity on the processes of land degradation in the past and may enable the improvement of future planning strategies.Based on the multi-temporal remotely sensed data in 1977,1987,2000 and 2004, this study analyzed the land use change characteristics in the Qinghai Lake watershed from 1977 to 2004 and investigated the spatial difference of land use structures between different counties, by the using of transition matrix of land use types and land use dynamic degree. Then land use intensity in the Qinghai Lake watershed was calculated and compared with other typical regions in China. The conclusions of the study can be drawn as follows: (1) Land use change was characterized by constant land decrease for ecological function and land increase for production as well as degraded land from 1977 to 2004, for instance, the water body area decreased 292.70 km² in the last 30 years. (2) The increase of farmland and sand derived respectively from occupying the grassland and transferring from the lake sand due to the decline of water level in the Qinghai Lake, the sand area increased 103.22km²because of the decline of water level from 1977 to 2004. (3) The changing rate of farmland area,residential area,sand area and forest area has been slowed down since 1977 while the water area decreased obviously from 2000 to 2004 (0.71%)and the grassland area changed slowly all the year round. On the whole watershed, the changing rate of all the land use types had the characteristics of interannual variation. (4) The differences of land use structures between four counties were obvious with most of the sand distributed in Haiyan (more than 70%),at the same time, Gangcha and Gonghe had 90% of forest and more than 95% of farmland of the whole watershed, moreover, changes of land use structures were various between these four counties. (5)The variation of land use intensity in the Qinghai Lake watershed was insignificant from 1977 to 2004 while the average value of integrated index is 186.47. The comparison of land use intensity between the Qinghai Lake watershed and other typical regions showed that human activity had little effect on the land use/cover change in this study region, so the related researches on regional environmental and ecological problems should pay more attention to the driving process of natural factors.