中文摘要：

北方13省处在干旱、半干旱和半湿润地区,植被对气候变化和人类活动最为敏感,一直是荒漠化研究的热点地区。基于GIMMS NDVI和降水数据,使用一元线性回归方法对北方13省1982年-2006年ΣNDVI和降水的年际变化趋势及其相关性进行了分析,并对ΣNDVI和降水的变化趋势差异做进一步分析。研究结果表明：从总体上来看,中国北方13省在25年间荒漠化趋势变缓,即植被覆盖度呈显著上升趋势,其中显著增加的像元数为35.3%,而显著降低的像元数仅占7.2%。从ΣNDVI与降水的斜率散点象限图来看,ΣNDVI和降水的差异主要在第二象限和第三象限,说明尽管降水在北方地区植被覆盖度变化中起到主要作用,但是降水并不能完全解释植被覆盖度的变化趋势,人类活动如植树造林等是植被覆盖度增加的重要驱动力。内蒙古自治区东北部和东北地区的三江平原呈现出荒漠化趋势,在大部分地区与降水的相关性不显著,表明在该地区降水的影响作用较弱,主要是人类活动等因素导致的。

英文摘要：

As one of the most sensitive region to climate change and human activities in arid,semiarid and subhumid areas,13 provinces in northern China have been recognized as a hot spot on desertification study. A linear regression method was performed to analyze the annual variations trends of GIMMS NDVI and precipitation data. And also,the correlation and anomaly of ΣNDVI and precipitation in northern province for the period of 19822006 were further investigated. The results showed that overall,the trend of desertification slowed down for the 13 provinces in northern China during the 25 years. The vegetation coverage was significantly down increasing,in which the number of pixels with significant increase were upto 35. 3%,and the decreased one accounted for only 7. 2%. ΣNDVI and precipitation anomaly were mainly in the second and third quadrant. This indicates that despite the precipitation played a major role in vegetation changes in the northern region,it did not fully explain the increasing trend of vegetation. In addition to precipitation,vegetation increase was also influenced by anthropogenic factors,such as afforestation activity,which was an important driving force. The northeastern part of Inner Mongolia and Sanjiang Plain of Northeast China showing the trend of desertification,no significant correlation in most parts of the precipitation,indicating that the effect of precipitation in the region was weak,mainly aused by human activities and other factors.