21世纪初中国生态退耕的空间格局及黄土高原典型区退耕的生态位适宜性分析(英文)

自1999年我国开始试行以"退耕还林"工程为主的生态退耕以来,到目前已历时十年。特别是进入21世纪,工程实施强度较大,因此从国家尺度上进行宏观生态退耕格局的分析对于评估生态退耕政策和确定未来政策导向具有重要意义。本研究以TM遥感监测的土地利用变化数据库为基础分析2000-2005年生态退耕的时空格局。在此基础上,以黄土高原典型地区陕西中北部为研究区,采用生态位适宜度评价模型探讨了生态退耕工程实施的合理性。研究结果表明:(1)2000-2005年间,生态退耕主要集中在中国中部地区,尤其是在黄河和长江的中上游地区,生态退耕面积与建设占用面积基本持平。在各生态类型区中,黄土高原土壤侵蚀区生态退耕面积最大,达到了1162.50km~2,主要用于还林;(2)整体看来,研究区内生态退耕的空间格局是合理的,即适宜性越差的耕地退耕比例越大。从退耕区域的适宜性水平来看,有77.35%的地区属于勉强适宜区,其中退为林地的面积为603.32km~2,退为草地的面积为528.94km~2。整个研究区内前者大于后者。然而,退耕地中仍有19.38%属于中度适宜区,原因可能来自于退耕指标分配等管理因素,另外,当地农民外出务工从而将中等适宜度的耕地退耕。结果表明,当前仍有大面积不适宜和勉强适宜的耕地存在,在未来工程实施过程区应该首先考虑该类地区。

China's Sloping Land Conversion Program at the Beginning of 21st Century and Its Habitat Suitability in Typical Region of Loess Plateau

The largest ecological restoration project in the form of Sloping Land Conversion Program (SLCP) been implemented for about ten years in China since 1999. Nationwide research on Sloping Land Conversion (SLC) policy needs to examine especially at the beginning of 21st century, because the project has been implemented on unprecedented scale in this period. This study tried to monitor the spatial pattern of ecological SLC using land use change dataset from human-aided interpretation of Landsat TM images.Quantity and spatial pattern of SLC (2000-2005) including two types of conversion, namely "converting cultivated land into forest" and "converting cultivated land into grassland" was analyzed. A case study of Middle and Northern Shaanxi Province, which is one of the most typical region of Loess Plateau, was investigated to analyze the rationality of the project implementation based upon the two types of conversion. The model of habitat suitability for cropping was used for the rationality evaluation of SLCP.The results showed that: (1) SLCP was concentrated mainly in the central regions of China, especially in the middle reaches of Yangtze River and Yellow River, and SLC covered nearly a half of the total cropland loss; the soil erosion zone of Loess Plateau had a large area of sloping lands which was estimated about 1162.50 km2, and more than half of them for forestation; (2) the spatial location of the projects was rational on the whole, and the cropland with lower suitability levels had a higher area proportion convered. The proportion of sloping lands conversion in marginal suitability level was the largest and covered 77.35 % of all the SLCP area, of which 603.32 km2 was converted into forest lands and 528.94 km2 of that into grasslands. There was more croplands converted into forest than into grassland. The converted cropland area with moderate suitability still had a percentage of 19.38, and the possible reason was due to the management factor and target allocation of SLCP. Furthermore, local farmers set aside cropland, and then worked in cities for more subsides. There was still a large areas of cropland unsuitable and marginally suitable, which should be considered to be converted first of all in the future.