基于GIMMS NDVI的青藏高原植被指数时空变化及其气温降水响应

青藏高原植被生态系统脆弱， 是研究全球气候变化陆地植被生态系统响应的理想场所。以GIMMS NDVI、 气温和降水及植被类型数据为基础， 利用一元线性回归模型、 相关系数、 偏相关系数及t检验方法， 分析了青藏高原1982 - 2015年NDVI时空变化及其气温降水响应特征， 结果表明： 1982 - 2015年青藏高原NDVI时间变化过程总体表现为不显著的增加过程， 空间变化以显著增加为主， 占总面积的63.26%， 分布在高原北部、 西部和南部； 显著减少集中分布在高原中东部和东南部， 仅占总面积的3.45%。青藏高原主要植被类型NDVI平均值表现为： 阔叶林>针叶林>灌丛>草甸>高山植被>草原>荒漠， 其中草原、 高山植被和荒漠植被NDVI呈显著线性增加过程， 灌丛、 针叶林和阔叶林植被的NDVI呈不显著的减少过程。青藏高原NDVI与气温相关系数空间上呈南北向分布， 具有纬度地带性特征， 显著正相关分布在高原中北部， 显著负相关分布在高原中南部； NDVI与降水的相关系数呈东西向分布， 具有干湿度地带性特征， 显著正相关分布在高原中部， 显著负相关分布在高原东西两侧。研究认为1982 - 2015年青藏高原北部水热条件缺乏区域NDVI出现显著增加趋势， 而高原东南部水热条件充足地区NDVI呈现出显著减少趋势。深入开展植被类型NDVI气候响应的差异性研究， 有助于深入理解全球气候变化影响的区域差异及科学制定植被生态保护政策。

Spatial and temporal changes of vegetation index and their response to temperature and precipitation in the Tibetan Plateau based on GIMMS NDVI

The vegetation ecosystem on the Tibetan Plateau is vulnerable under global and regional climate changes. It is an ideal place to study the response of terrestrial vegetation ecosystems to global climate change. Based on GIMMS NDVI， temperature and precipitation， and vegetation type data， the linear regression equation， correlation coefficient， partial correlation coefficient and t-test method were used to analyze the temporal and spatial variations of NDVI and their responses to the variations of temperature and precipitation on the plateau from 1982 to 2015. The result showed that： （1） The temporal change process of NDVI in the plateau from 1982 to 2015 showed an insignificant increase process， while the spatial change process was increased significantly， accounting for 63.26% of the total area， mainly in the north， west and south of the plateau， such as the west and north of Qinghai Province， southern Xinjiang Region， western and southern Tibet. A significant reduction was concentrated in the southeast， such as the eastern part of Tibet， the southern part of Qinghai Province， the western part of Sichuan Province and the border areas of the three provinces （region）， accounting for only 3.45% of the total area； （2） The average NDVI of the main vegetation types on the plateau were broad-leaved forest > coniferous forest > shrub > meadow > alpine vegetation > grassland >semi-desert， in which NDVI of grassland， alpine vegetation and semi-desert vegetation having a significant linear increase， while the NDVI of shrub， coniferous and broad-leaved forest vegetation having less significant reduction； （3） The spatial distribution of NDVI and temperature correlation coefficient on the plateau was north-south， with the characteristics of latitude and zonal. The significant positive correlation was distributed in the central and northern part of the plateau， while the significant negative correlation was distributed in the central and southern part of the plateau. The correlation coefficients between NDVI and precipitation distributed in an east-west direction with dry zonal characteristics， and a significant positive correlation distributed in the middle of the plateau， while the significant positive correlation distributed in the east and west sides of the plateau. The following conclusion can be drawn that the NDVI in poor hydro-thermal condition in the northern part of the plateau had increased significantly from 1982 to 2015， but had a significant reduction in the areas with sufficient hydro-thermal conditions. Further research on the NDVI and their response to climate change in different vegetation regions will help to understand the regional differences in global climate change and scientifically formulate vegetation ecological protection policies.