Vegetation change and its responses to climatic variation based on eco-geographical regions of Tibetan Plateau

This paper investigated the variation trend of annual average NDVI both in the overall Tibetan Plateau and in different eco-geographical regions.The spatial characteristics of the response of NDVI to climatic factors(temperature and precipitation) in different eco-geographical regions were assessed based on a half-month maximum synthesis GIMMS NDVI dataset and climate data from 104 meteorological stations during 1982-2006.The results showed that:(1) The vegetation coverage tended to improve on the whole in the past 25 years,especially in the northeastern and southwestern plateau,and the middle part of the eastern plateau,which belonged to the humid and semi-humid regions.But the vegetation degradation happened in the northern and western plateau,which belonged to semi-arid and arid regions.(2) The correlation between vegetation change and temperature variation was relatively large,which showed that the response of vegetation change to temperature variation was more sensitive than to precipitation.(3) The correlation between vegetation change and temperature and precipitation variations was obviously different in different eco-geographical regions.The greatest correlation was shown in the moderate vegetation cover region,and it gradually weakened from meadows and steppes to coniferous forests.The relevance of desert was the smallest.The correlation between vegetation cover and temperature during growing seasons was consistent with that throughout the year,but was greatly different from the correlation with precipitation that was not significant during growing seasons.