北方农牧交错带土地利用变化及其生态环境效应--以陕北榆林市为例

基于1985～2000年间的高分辨率土地利用/土地覆盖数据,对位于农牧交错带的陕北榆林市土地利用变化及其区域生态环境效应进行定量分析.结果表明:1985～2000年,榆林市土地利用变化区域差异明显,土地利用变化多分布在北部风沙滩地区,表明这些地区的土地利用变化过程相对活跃.生态环境质量总体上得到改善,但局部地区恶化也相当严重,且在县级尺度上表现出明显的区域分异特征.在大的区域尺度上北部风沙滩地区的生态环境质量的改善程度强于南部丘陵沟壑区.导致生态环境变化(改善和退化)的主导因素是林地、草地与其它土地利用/土地覆盖类型之间的转变,其中治沙种草与防护林体系建设对该市生态环境质量改善的贡献率最高,达到74.8%.

The Land Use Change and Its Eco-environmental Effects in Transitional Agro-pastoral Region--A Case Study of Yulin City in Northern Shaanxi Province

Based on the data of land use/land cover of Yulin in northern Shaanxi, the process of land use change and its eco-environmental effects were quantified and analyzed, the results indicate: the land use pattern had a large change in the last 15 years. Farmland decreased by 405.98 hm2, and forestland and grassland increased by 17 157.02 hm2 and 107 975.17 hm2. The transitional quantities of no use land to grassland are the largest, and the following is degradation of grassland. The general quality of regional eco-environment has improved in the last 15 years. However, the trends of both improvement and degradation in eco-environment were coexist, and displayed their spatial heterogeneity in county-level. The land use change in Yulin has obvious regional difference, and in north wind-sand area the change is more serious and the process of land use change is more active. The spatial rule of eco-environmental effect caused by land use change presents: wind-sand area in north has a better improvement in eco-environment than that of hilly-donga in south. The main factors causing eco-environment change of improvement and degradation are transition of forest and grassland, and tree planting and forestation have the most distribution to the improvement of eco-environment, with its distribution ratio 74.8%.