近10a青藏高原干湿状况及其与植被变化的关系研究

Wet-drought pattern and its relationship with vegetation change in the Qinghai-Tibetan Plateau during 2001-2010

植被是陆地生态系统中最重要、同时也是气候变化最敏感的组分,而高原植被系统行为往往比其他地区能更早、更明显地预兆全球变化。探讨青藏高原区域干湿状况及其与植被变化的关系有助于更好地认识和理解陆地生态系统对气候变化的响应和适应机理,对高原生态安全屏障计划的实施以及全球生态建设有重要意义。基于地面气象台站观测数据和MODIS EVI数据集,2001-2010年生长季干湿状况和植被覆盖的时空变化格局,对青藏高原干湿状况与植被覆盖变化的关系进行了分析与探讨。结果表明:(1)高原整体上呈现由东南向西北渐干的趋势,干旱及半干旱区占高原总面积的67%。10 a间高原有25%的区域在逐渐变干,且南北差异明显;(2)高原生长季EVI的空间格局与干湿格局相近,且东西部界线分明。10 a间高原植被活动由东南向西北整体上呈现"退化-增强-变化不大"的规律;(3)区域干湿程度对EVI空间格局差异有显著影响,特别是在占高原面积44%的半干旱区,两者相关性最大。人为干扰对高原EVI变化的作用不明显,但EVI与干湿程度相关性相对偏小的区域人为干扰程度往往较大;(4)从高原96个气象站点生长季EVI对干燥度指数变化的敏感性来看,敏感程度较大的气象站点主要集中在高原东北部、高原中部及雅鲁藏布江中上游区域,60%以上的气象站点随着干旱程度的加深植被呈退化趋势。

As one of the striking characteristics of global change,regional dry-wet climate variations and its effects on ecosystems has become one of the most important environment problems being faced by the world,and has been the focus and the advancing edge of global change study.Qinghai-Tibetan Plateau（QTP）is both a climate change frontier and natural defense of stable climate system of China and around the world.However,impacted by the global warming and anthropogenic activities,the ecological environment problems is showing up gradually,and the ecological shelter zone is seriously threatened.Vegetation is the most important and the most sensitive composition of climate change,and compared to other regions,the action of the vegetation system can have earlier and more obvious indicating effects of global change.The study of regional dry-wet status of the QTP and its relation to the vegetation changes will improve our understanding of the response and adaptation mechanisms of terrestrial ecosystems to climatic change,and also will have very important implications to the implementation of the scheme of ecological shelter zone and contribute to global ecosystem management activities.In this study,the model of RFE 2.0 and Penman-Monteith were used to estimate the precipitation and potential evapotranspiration of the QTP in growth season of the last ten years,respectively.Then based on the aridity index derived from the precipitation and potential evapotranspiration,the temporal and spatial character and the relationship between variations of regional dry-wet climate and vegetation change were explored and discussed.The results showed as follows：（1）Aridity index of QTP increased from SE to NW in general,with 67% of the entire plateau belonging to arid and semiarid regions.Over the ten-year period,about 25% of the area become drier,and obvious difference was detected between the north and the south for the drought trend;（2）The spatial pattern of EVI during the growing season were similar to that of drought,showing clearly defined boundaries for the western and eastern.About 25% of the area present obvious vegetation degradation during the last 10 years.（3）The degree of wet-dry has significant influence on the vegetation distribution of QTP,especially in the semi-arid areas which covered 44% of the whole plateau,the correlation coefficient between both was the biggest,the effect of Human disturbance on the vegetation distribution was not very apparent,but there was a relatively weak relationship between aridity index and EVI in the area with intensive human interferences;（4）In terms of the sensitivity of vegetation to the changes of wet-drought,The higher sensibility of EVI to aridity index of 96 meteorological sites during the growing seasons was distributed mainly in northeast and central plateau,and also along the upstream of Brahmaputra River,and as drought conditions worsen,the vegetation of more than 60% of those meteorological sites were degenerated in the nearly 10 years.