2000-2018年间青藏高原植被覆盖变化及其与气候因素的关系分析

探讨全球气候变化背景下青藏高原地区植被覆盖变化及其驱动因素，对加深全球气候变化的认识和生态环境保护具有重要的生态价值和现实意义。本研究利用2000-2018年中尺度分辨率成像光谱归一化植被指数（Moderate Resolution Imaging Spectroradiometer Normalized Difference Vegetation Index，MODIS NDVI）1 km·月^-1分辨率数据以及气象观测数据，采用最大合成法、趋势性分析以及相关分析方法，探讨了青藏高原地区NDVI的时空变化趋势及其与气温、降水的关系。结果表明，近19a来，青藏高原地区NDVI呈增加趋势。从地理单元来看，低植被覆盖区主要分布于西藏大部、新疆南部和甘南局部以及青海西北部；中植被覆盖区主要位于青海与甘肃、西藏、四川和云南的交汇区域；高植被覆盖区主要分布在四川和云南西北部、青海和甘南以及藏东南局地。除局部地区植被有所退化，大部地区植被生长良好，且植被改善的面积大于植被退化。因此，青藏高原植被整体呈稳定恢复状态。青藏高原地区NDVI与同期气温和降水均显著相关，但与气温的关系更密切。气温每升高1℃，NDVI增加0.128；降水每增加100 mm，NDVI增加0.172。

Analysis of Vegetation Coverage Change and Its Driving Factors over Tibetan Plateau From 2000 to 2008

Studing vegetation coverage change and its driving factors over the Tibetan Plateau under the context of global climate change has an important ecological value and practical significance,and contributes to understanding global climate change and ecological environment protection deeply. Using the monthly moderate resolution imaging spectroradiometer normalized difference vegetation index,(MODIS NDVI) with 1 km resolution from 2000 to 2018,and meteorological observation data,this study analyzed the spatio-temporal variation trends of the NDVI and its relationship with precipitation and temperature over the Tibetan Plateau based on maximum value composites (MVC),linear trends and correlation analysis method. The results showed that NDVI of the Tibetan Plateau had been increasing over the past 19 years. From the perspective of geographical units,the low vegetated areas mainly distributed in most parts of Tibet,parts of Xinjiang and Gansu,and parts of northwest Qinghai. The area of medium vegetation coverage mainly located in the intersection of Qinghai,Gansu,Tibet,Sichuan and Yunnan. The high vegetation coverage area mainly distributed in Sichuan and most parts of Yunnan,Qinghai and Gansu as well as some parts of southeastern Tibet. Only a small part of vegetation over Tibetan Plateau was still degrading,most of them had been improved,the total area of improved vegetation growth in the whole Tibetan Plateau was larger than that of degraded. Therefore,the vegetation of Tibetan Plateau was in a steady state of recovery. NDVI was significantly correlated with temperature and precipitation over the same period,but it is more closely correlated with temperature than precipitation. NDVI increased 0.128 per 1℃ increase in temperature and increased 0.172 per 100 mm increase in precipitation.