Responses Of Vegetation Coverage To Climate Change On The Loess Plateau Based On AVHRR/NDVI And Its Quantitative Analysis

This paper, by basing on NOAA/AVHRR NDVI8km data between1982and2006,along with rainfall and temperature data of82meteorological stations on Loess Plateauand its surrounding places, has discussed the vegetation cover, changing characteristics ontime and space of major climatic factors and their mutual response regularity; moreover,the influence and contribution degrees of human activities and climate changes on regionalvegetation cover are analyzed with residual analysis. Major conclusions of this paperinclude:1) from1982to2006, vegetation cover of Loess Plateau rose insignificantly andvegetation cover did not go through any big change; the linear trend of average vegetationcover in four seasons were positive; the area of unchanged vegetation cover was taking upmore than85.29%, a level of low and medium vegetation cover; the area of improvedvegetation area was taking up9.17%; the area of vegetation degradation was taking up5.54%. According to a core evolution analysis, the core positions of low and mediumvegetation cover and high vegetation cover were mainly kept unchanged, the coveragelevels of medium and high vegetation, medium vegetation and low vegetation movedtowards directions of east, northwest and southeast respectively.2) meanwhile, the annual rainfall of Loess Plateau declined insignificantly, in anaverage rate of1.9mm/a; the rainfalls in the four seasons declined insignificantly thoughrainfall in summer season declined most obviously; the annual average temperature onLoess Plateau rose significantly (p<0.001), at a rate of0.7℃/10a; temperatures in the fourseasons were on the rise and temperatures in spring and summer rose significantly(p<0.01); the climate was changing toward warmer and dryer.3) the partially correlation between vegetation covers and annual rainfalls and annual average temperatures were significant but spatial difference was obvious; the area in whichthe vegetation covers on Loess Plateau were positively related to rainfall in space wastaking up85.9%, of which22.3%reached the level of significant correlation(p<0.05); thearea in which vegetation covers were positively related to temperatures was taking up68.7%, of which17.6%reached the level of significant positive correlation (p<0.05);vegetation growth was very sensitive to the response of precipitation factors.4) from1997to2006, the contribution rate of human activities to vegetation growthwas about20%while the that of climate changes was as high as80%.