This paper, by basing on NOAA/AVHRR NDVI 8 km data between 1982 and 2006,
along with rainfall and temperature data of 82 meteorological stations on Loess Plateau
and its surrounding places, has discussed the vegetation cover, changing characteristics on
time and space of major climatic factors and their mutual response regularity; moreover,
the influence and contribution degrees of human activities and climate changes on regional
vegetation cover are analyzed with residual analysis. Major conclusions of this paper
1) from 1982 to 2006, vegetation cover of Loess Plateau rose insignificantly and
vegetation cover did not go through any big change; the linear trend of average vegetation
cover in four seasons were positive; the area of unchanged vegetation cover was taking up
more than 85.29%, a level of low and medium vegetation cover; the area of improved
vegetation area was taking up 9.17%; the area of vegetation degradation was taking up
5.54%. According to a core evolution analysis, the core positions of low and medium
vegetation cover and high vegetation cover were mainly kept unchanged, the coverage
levels of medium and high vegetation, medium vegetation and low vegetation moved
towards directions of east, northwest and southeast respectively.
2) meanwhile, the annual rainfall of Loess Plateau declined insignificantly, in an
average rate of 1.9mm/a; the rainfalls in the four seasons declined insignificantly though
rainfall in summer season declined most obviously; the annual average temperature on
Loess Plateau rose significantly (p<0.001), at a rate of 0.7℃/10a; temperatures in the four
seasons 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 which
the vegetation covers on Loess Plateau were positively related to rainfall in space was
taking up 85.9%, of which 22.3% reached the level of significant correlation(p<0.05); the
area in which vegetation covers were positively related to temperatures was taking up
68.7%, of which 17.6% reached the level of significant positive correlation (p<0.05);
vegetation growth was very sensitive to the response of precipitation factors.
4) from 1997 to 2006, the contribution rate of human activities to vegetation growth
was about 20% while the that of climate changes was as high as 80%.
Key words: Loess Plateau area; climate change; vegetation cover; human activity