近20年黄土高原土地利用/覆被变化特征分析

本文根据黄土高原地区20世纪80年代末、2000年、2008年3期土地利用/覆被空间数据集,计算2个时段（20世纪80年代末-2000年,2000-2008年）土地利用/覆被转类方向及其幅度、土地利用/覆被转类指数、土地利用/覆被状况指数及其变化率,分析黄土高原地区自20世纪80年代末以来土地利用/覆被时空变化特征以及宏观生态状况的变化趋势。结果显示：黄土高原地区近20年来平均土地利用/覆被状况指数为24.07,其中土石山区生态系统综合功能最好,其次为河谷平原区,最差的为农灌区。20世纪80年代末-2000年,黄土高原地区主要土地利用/覆被转类是森林和草地转为耕地,生态级别由高级向低级转移,2000-2008年主要土地利用/覆被转类是耕地转为林地和草地,低覆盖草地转为中高覆盖草地,生态级别由低级向高级转移。近20年来黄土高原地区地覆被状况指数变化以及土地利用/覆被转类指数表明,该区域的宏观生态状况总体上经历了转差（20世纪80年代末-2000年土地利用/覆被转类指数为-1.08）,后转好（2000-2008年土地利用/覆被转类指数为2.66）2个过程。这一变化过程前期受区域气候变化以及人口增长共同驱动,后期则叠加了生态工程的影响。

Characteristics of Land Use and Land Cover Change in the Loess Plateau over the Past 20 Years

Based on the three phases of land use and land cover change spatial data sets for the late 1980s, 2000 and 2008 in the Loess Plateau, we calculated the direction and amplitude of land cover change, land cover condition index and land cover change index, and analyzed the temporal and spatial characteristics of land cover and macro-ecological conditions changes in the Loess Plateau since the late 1980s. The results showed that the average land cover condition index of the Loess Plateau was 24.07 in the last 20 years. Land cover condition of the Rocky Mountain Area was the best, the Valley plain area took the second place, and the Agricultural Irrigation Area had the worst land cover condition. From the late 1980 s to 2000, the major land cover change was the conversion from forest and grassland to farmland, with the ecological grade transformed from the high grade to the low grade. From 2000 to 2008, the main land cover change was the conversion from cultivated land to forest and grassland, and the transition from low coverage grassland to high coverage grassland, with the ecological grade transformed from the low grade to the high grade. In the last 20 years, the land cover condition index and land cover change index indicated that the macro-ecological condition had experienced a slip period (1980 s to 2000 period LCCI-1.08), and then a meliorated period (2000 to 2008 period LCCI 2.66). This transformation was firstly driven by the climate change and population growth, and later was superimposed by the effect of ecological engineering.