中文摘要：

三北防护林体系工程是我国重点林业生态工程,其数量与空间分布格局影响着整个三北地区的生态环境.为科学、客观、完整地评价三北防护林体系工程建设30年来（1978—2008）片状防护林的数量与空间分布格局,本文采用多元遥感影像对三北地区片状林面积估算方法进行了研究.首先,利用TM影像（分辨率30m）监测2008年三北地区片状防护林面积;再基于随机取样原理,建立不同降水气候区的高分辨率影像（SPOT5,分辨率2.5m）与TM影像在片状防护林面积监测的校正关系;最后利用前两部分结果估算出2008年三北地区片状防护林面积.结果表明：截至2008年,三北地区片状防护林（乔木林郁闭度〉0.3,灌木林覆盖度〉40%,精确度约85%）总面积328360.03km2.其中,东北区116244.55km2,华北区42981.32km2,黄土高原区76767.05km2,蒙新区92367.11km2.按照防护林树种统计,针叶林62614.74km2,阔叶林121628.51km2,针阔混交林22144.09km2,灌丛121972.69km2.

英文摘要：

The Three-North Shelter Forest Program is a key forestry ecological project in China. The quantity and spatial distribution of the shelter forest in the program affect the ecological environment of the entire Three-North region. In this paper, multi-sensor remote sensing data were used to scientifically, objectively and comprehensively estimate the quantity and spatial distribution pattern of the shelter forest in this region in 1978-2008. Firstly, the Landsat TM images （30 m in resolution） were adopted to extract the shelter forest data in this region in 2008. Then, based on random sampling techniques, the calibration formulae for the shelter forest area in different precipitation climate regions estimated by the SPOT5 （2.5 m in resolution） and Landsat TM were constructed. By using the above-mentioned results, the shelter forest area in the Three-North region in 2008 was estimated. In 2008, the total area of the shelter forest （canopy density of arbor shelter forest was 0.3, coverage of shrub shelter forest was 40%, and accuracy was about 85%） in this region was 328360.03 km2, with 116244.55 km2 in Northeast China, 42981.32 km2 in North China, 76767.05 km2 in Loess Plateau, and 92367.11 km2 in Mongolia-Xinjiang Region. According to the classification of shelter forest types, the areas of coniferous forest, broadleaved forest, mixed broadleaf-conifer forest and shrubland were 62614.74, 121628.51, 22144.09 and 121972.69 km2, respectively.