基于生态地理分区的青藏高原植被覆被变化及其对气候变化的响应

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

基于1982～2006年GIMMS NDVI数据集和地面气象台站观测数据,分析了青藏高原整个区域及各生态地理分区年均NDVI的变化趋势,并通过偏相关分析研究不同生态地理分区植被覆被变化对气温和降水响应的空间分异特征。研究表明:(1)近25年来,高原植被覆盖变化整体上趋于改善;高原东北部、东中部以及西南部湿润半湿润及部分半干旱地区植被趋于改善,植被覆盖较差的北部、西部半干旱和干旱地区呈现退化趋势;(2)高原植被变化与气温变化的相关性明显高于与降水变化的相关性,说明高原植被年际变化对温度变化更为敏感;(3)高原植被年际变化与气温和降水的相关性具有明显的区域差异,植被覆盖中等区域全年月NDVI与气温和降水的相关性最强,相关性由草甸向草原、针叶林逐步减弱,荒漠区相关性最弱。生长季植被覆盖变化与气温的相关性和全年相关性较一致,降水则不同,生长季期间高原大部分地区植被变化与降水相关性不显著。

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.