北京风沙源区土地退化及其趋势分析

人类不合理的土地利用方式和程度是导致土地退化的主导因素,北京风沙源区土地退化动态变化直接影响我国北方地区沙尘暴的发生发展的频率与强度.基于1991年～2002年两个时相遥感数据提取近10年来北京风沙源区土地利用退化的动态变化数据,采用相应的土地退化评价指标和土地退化结构相对数与比较相对数,分析北京风沙源区土地利用退化动态变化的空间分布特征.北京风沙源区不同生态区内土地利用退化结构差别较大,内蒙古高原干旱草原生态区、坝上高原农牧生态区和阴山山脉农牧交错生态区以沙化退化为主,燕山山脉农业生态区和大同盆地及周边地区则主要是水蚀退化.分析表明,土地利用退化存在明显的地域差异,针对不同土地利用退化现状,草地沙化是亟待解决的问题,农牧交错带的土地退化具有相当强的政策和区域利益痕迹,在国家重大生态环境工程建设过程中需要特别注意协调.

Land Degradation in Surrounding Areas of Beijing and Its Changing Trend

The irrational human activities and land use patterns are the main factors causing land degradation. In case of the surrounding areas of Beijing, land degradation affects directly the frequency and intensity of sand & dust storm in Northern China. The case study region of surrounding areas of Beijing includes 51 counties of the three provinces and autonomous regions. Based on land use information and temporal change of land use degradation which were distilled from remote sensing image data in Beijing surrounding area during the last ten years, three indexes (i.e. the assessment index of land use degradation, construction relative index and compare relative index of land use degradation) has been used to analyze the dynamics of land use degradation in the study region. The results showed that great deal of land degradation appeared and there were large differences in land use degradation between different regions; e.g. the sandy desertification mainly existed in Inner Mongolia Plain, Yinshan mountain range, while water erosion distributed in Yanshan mountain area and Datong basin. The sandy desertification in farming-pastoral zone accounted for a high proportion of Beijing surrounding areas. Concerning that the farming-pastoral zone is ecologically vulnerable, so the degradation of vegetation would easily induce wind and water erosion, which would cause sandy desertification. In the long run, the water and soil loss could even trigger sand-dust storm. The past experience tells us that the irrational farming activities has degraded the resources and environments and therefore restricted sustainable development. It suggests that the current environmental projects invested by the central government should emphasize on the farming-pastoral zone of semi-arid area, and to eliminate serious soil desertification.