三北防护林工程区植被覆盖变化与影响因子分析

利用1982~2006年间GIMMS AVHRR NDVI植被覆盖数据和气象站点气候数据,分析了三北防护林工程区25a来植被覆盖的时空变化特征及其与气温、降水变化的相关性,并在此基础上通过采用残差分析法探讨了人类活动对研究区植被覆盖变化影响的空间格局.结果表明:研究区25a的年植被变化量增加幅度略大于减少幅度,植被覆盖整体呈缓慢上升趋势,其中Ⅰ区和Ⅳ区NDVI值上升最明显(P<0.001),Ⅱ区则呈微弱下降趋势,而四大建设区植被覆盖度有不同程度提高;研究区植被和气温、降水整体呈正相关关系,17.74%的地区植被与气温呈负相关,而6.84%的地区呈正相关,10.60%的地区植被与降水呈负相关,19.53%的地区则呈正相关,植被与降水正相关面积明显大于植被与气温正相关面积,说明降水是研究区植被生长的关键因子;研究区植被残差年际变化显著正相关面积大于显著负相关面积,人类活动对植被建设作用要强于破坏作用,三北防护林建设工程带来的生态效益正在呈现.

Analysis of the vegetation cover chang and its relationship with factors in the Three-North Shelter Forest Program

The Shelter Forest System Program(TNSEP) in Three-North Region of China is the largest ecological reforestation program in the world.The TNSFP vegetation research not only has important ecological environment meaning,but also attaches profound social and economic significance.Spatio-temporal variation of the vegetation coverage and its relationship with major climatic factors(temperature and precipitation) in TNSFP was explored by using GIMMS/NDVI dataset at 8km spatial resolution and climatic data during the period from 1982 to 2006.The results show that: 1) vegetation cover had an entirely rising trend during the past 25 years,the increasing rate of vegetation variation was slightly higher than reducing rate,Ⅰand Ⅳ NDVI increased most significantly P<0.001),while Ⅱ showed a slight downward trend.Moreover,the vegetation coverage of four construction regions has been improved in different degree.2) Vegetation cover,temperature and precipitation overall were positively correlated on the study area.The temperature and vegetation cover was negatively correlated in 17.74% of the region,but 6.84% of the region was a positive correlation.The precipitation was negatively correlated with vegetation cover in 10.60% of the region while 19.53% of the region was a positive correlation.Vegetation associated with the precipitation was significantly larger than the area related to temperature,precipitation was the key to factor vegetation growth on the study area.3)Inter-annual residuals of vegetation variation showed a significant positive correlation area which was greater than the area of a significant negative correlation area,and the role of human construction on vegetation was stronger than the destructive role.Therefore,the positive impact of TNSFP ecological construction was showing.