中文摘要：

本文基于1982年-2006年连续25a的GIMMS AVHRR NDVI植被覆盖指数,采用了最大化NDVI均值法、提取植被覆盖度法和一元线性回归趋势分析方法,对中国三北防护林工程区的四大建设区（风沙区,西北荒漠区,黄土高原丘陵沟壑区和东北、华北平原区）连续25a的植被覆盖时空变化特征进行了动态变化研究。结果表明：①近25a来,研究区植被NDVI平均值总体呈缓慢上升趋势,增速为0.007/10a,其中风沙区和东北、华北平原区植被增速最明显,而西北荒漠区植被呈微弱下降趋势;②四大建设区植被覆盖度有不同程度提高,其中黄土高原沟壑区植被覆盖度上升最快,比1982年提高了9.66%;③在1982年-1991年、1992年-2001年、2002年-2006年三个时期内,大兴安岭中、南部,小兴安岭中部,长白山东北段,燕山,辽西低山丘陵区,阿尔泰山,天山,祁连山东段,西北荒漠区东部和黄土高原丘陵沟壑区南部等地区的植被覆盖面积分别增加了472994km2、451032km2、435196km2;而在相同的三个时期,大兴安岭两侧,呼伦贝尔高原西部,三江平原北部,科尔沁沙地南端,西北荒漠区南部和黄土高原丘陵沟壑区北部等地区的植被覆盖面积分别减少了197717km2、270192km2、182690km2。

英文摘要：

The Shelter Forest System Program in the Three-North Regions of China （the Three-North Shelter Forest Program, TNSFP） is the largest ecological reforestation program in the world, and has made great achievements since it was initiated in 1978. It covers 13 provinces and 551 counties of China, with longitude ranging between 73°26’ E and 127°50’ E and latitude ranging between 33°30’ N and 50°12’ N, covering an area of 4.069×106 km2 which accounts for 42.4% of China’s territory. It was projected to span from November 1978 through December 2050, lasting 73 years, and can divided into three phases and eight stages of construction. The total planning afforestation has been amount to be 0.351×106 km2. Research on vegetation for TNSFP would be of great value to the environment and social and economic development across these regions. In this paper, GIMMS AVHRR Normalized Difference Vegetation Index （NDVI） datasets, a globe dataset with 8-km spatial resolution （square pixels） which was developed by the Global Inventory Monitoring and Modeling Studies （GIMMS） group, was selected as the data source. The spatio-temporal variation in vegetation coverage of the Three-North Regions of China was systematically studied using the NDVI average method, retrieval of vegetation cover, and linear regression trend analysis during the period 1982-2006. Results show that： 1） over the past 25 years, NDVI vegetation of the study area showed a consistently increasing trend, with a growth rate of 0.007/10a. The growth of NDVI across the Sandy Area and the Northeastern and North China Plains was obvious, but the Northwestern Desert Area showed a subtle decreasing trend. 2） The vegetation coverage of four construction regions has been improved to varying degrees. Moreover, the Gully Region of the Loess Plateau was the fastest, with vegetation coverage being improved by 9.66%. 3） In the three periods 1982-1991, 1992-2001 and 2002-2006, vegetation coverage area across the study area has been increased by 47