摘要:退耕还林还草工程作为我国投资最大、涉及面最广的一项重大生态工程，其生态经济社会效应是行业部门及学术界关注的焦点。选择退耕还林还草面积、植被覆盖度、土壤侵蚀量作为指标，依据遥感反演和模型模拟得到的结果，分析了2000-2015年县域退耕还林还草时空差异，退耕还林还草区域植被覆盖度与土壤侵蚀变化及其对县域生态状况变化的贡献，并基于规划目标评估了退耕还林还草工程的宏观生态效应及其地域分异特征。结果表明：（1）近15年，工程区耕地转林地面积12.75万km²，耕地转林地区域植被覆盖度年增加0.32%、土壤水蚀和风蚀模数分别年减少0.43 t/hm²和0.21 t/hm²。（2）耕地转草地面积9.43万km²，耕地转草地区域植被覆盖度年增加0.43%，土壤水蚀和风蚀模数分别年减少0.55 t/hm²和0.94 t/hm²。（3）工程区全县域植被覆盖度年增加0.17%，平均土壤水蚀和风蚀模数分别年减少0.13 t/hm²和0.68 t/hm²。（4）遥感估算结果与工程规划目标相比，退耕还林的面积完成率达到87%，工程区林草覆盖率增加4.8%-6.5%，工程区平均土壤水蚀和风蚀模数逐年减少，大部分县域15度及以上坡耕地退耕比例超过50%。工程在黄土丘陵沟壑、东北山地及沙地、云贵高原等区域凸显了提高植被覆盖度与土壤抗蚀效应的正面作用。



Abstract:As one of the largest investment and extensive ecological restoration and conservation projects in China, the ecological and socioeconomic effects of the Grain for Green Project are the hotspots of policy makers, managers and academics. In this paper, the areas of cropland transferred to forest or grassland, vegetation coverage and soil erosion amount were selected as indicators. The regional characters of ecosystem changes due to the project from 2000 to 2015 were analyzed. The macro ecological effects of the project were evaluated based on the project planning objectives. The results showed that (1) in the past 15 years, the areas of cropland transferred to forest and grassland were 12.75×10⁴ km² and 9.43×10⁴ km² respectively, mainly occurred in the hilly-gully region of the Loess Plateau, the mountain and sand area in Northeastern China, the arid and semiarid regions in Northern China, and Yunnan-Guizhou Plateau. (2) The average annual vegetation coverage increased by 0.17% in the project region, of which the vegetation coverage increased by 0.32% in the area of cropland transferred to forest and by 0.43% in the area of cropland transferred to grassland. It was obviously in the hilly-gully region of the Loess Plateau, the arid and semiarid regions in Northern China, and the arid desert regions in Xinjiang. (3) The average annual modulus of soil water and wind erosion decreased by 0.13 t/hm² and 0.68 t/hm² in the project region, respectively. In which, it decreased by 0.43 t/hm² and 0.21 t/hm² in the area of cropland transferred to forest, and decreased by 0.55 t/hm² and 0.94 t/hm² in the area of cropland transferred to grassland, respectively. It was also apparent in the hilly-gully region of the Loess Plateau, Yunnan-Guizhou Plateau, the hilly regions in Sichuan, Chongqing, Hubei and Hunan Provinces, and alpine canyon regions in Southwestern China. (4) Compared the remote sensing estimation with the project planning objects, the implementation rate of area for returning cropland to forest reached to 87%. The vegetation coverage of forest and grassland in the project region increased by 4.8%-6.5%. The average modulus of soil water and wind erosion in the project regions decreased year by year, and the proportion of sloping cropland over 15 degrees returning to forest or grassland exceed 50% in most counties. The positive effects of project on vegetation coverage and soil erosion resistance has been highlighted in the Loess Plateau, mountain and sand area in Northeastern China, and Yunnan-Guizhou Plateau.





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