2000—2021年青藏高原生长季植被敏感性的时空变异

为揭示青藏高原陆地生态系统对气候变化敏感性的时空变异性，基于植被敏感性指数(Vegetation Sensitivity Index, VSI),使用2000—2021年青藏高原6—8月生长季MODIS EVI和ERA5再分析资料的温度、降水和太阳辐射数据，首先探究了22年里青藏高原陆地生态系统敏感性的空间变异性及其主要气候驱动因素，其次探究了青藏高原VSI在P₁(2000—2006年)、P₂(2007—2013年)和P₃(2014—2021年)时期内VSI的时间变异性，研究表明：(1)2000—2021年青藏高原生长季VSI的空间异质性较强，其中东南部灌木和森林的VSI较高，而西北部高山荒漠、高山草原和高山草甸的VSI较低；(2)22年里温度、降水和太阳辐射分别主导着青藏高原55.89%、19.24%和24.87%地区的VSI变化，其中温度主导着东南部灌木和森林的VSI,降水主导着东北大部分地区高山草甸的VSI,而太阳辐射主导着西南大部分地区高山草原的VSI。时间变异性结果表明：(3)P₁—P

Spatio-temporal variability of vegetation sensitivity on the Qinghai-Tibet Plateau during the growing season from 2000 to 2021

To reveal the spatiotemporal variability of terrestrial ecosystem sensitivity on the Qinghai-Tibet Plateau, the spatial distribution of the ecosystem sensitivity and the climate factors to dominate vegetation growth on the Qinghai-Tibet Plateau from 2000 to 2021 were explored. To this end, Vegetation Sensitivity Index (VSI) was applied to the MODIS EVI and ERA5 reanalysis data including temperature, precipitation, and solar radiation. The timeframe of this study was restricted to the growing season with months from June to August. Moreover, the temporal variability of VSI was investigated for the period of P₁(2000-2006), P₂(2007-2013), and P₃(2014-2021), respectively. Results indicate that:(1) the spatial heterogeneity of VSI in growing season was strong on the QTP from 2000 to 2021. High VSI values were observed in shrubs and forests located in the southeastern Qinghai-Tibet Plateau. By contrast, low VSI values were found in alpine deserts, alpine grasslands, and alpine meadows grown in the northwestern Qinghai-Tibet Plateau. (2) During the whole investigation period, temperature, precipitation, and solar radiation dominated the VSI variation in 55.89%, 19.24%, and 24.87% of the Qinghai-Tibet Plateau, respectively. Specifically, temperature dominated the VSI of shrubs and forests in the southeast Qinghai-Tibet Plateau and precipitation controlled the VSI in most alpine meadows of the northeastern Qinghai-Tibet Plateau. Solar radiation regulated the VSI in most of alpine grasslands distributed in the southwestern Qinghai-Tibet Plateau. Temporal variability results show that:(3) During the periods of P₁, P₂, and P₃, the VSI increased and decreased continuously in 18.39% and 10.09% pixels, respectively. The VSI of alpine desert, alpine grassland, and alpine meadow remained unchange during the P₁-P₂ period while showed an increasing trend during the P₂-P₃ period. By contrast, the VSI of shrubs and forests displayed an increasing (P₁-P₂) and then a decreasing (P₂-P₃) trend. (4) A strong spatiotemporal heterogeneity of the VSI on the Qinghai-Tibet Plateau was observed in the three periods. The proportion of pixels where temperature dominated the vegetation growth in the three periods had a slight change during P₁-P₂ but was reduced in P₃, corresponding proportion values were P₁(58.15%), P₂(61.34%), and P₃(49.47%), respectively. Conversely, the proportion of pixels that precipitation played a dominate role increased from 18.57% (P₁) and 18.47% (P₂) to 26.64% (P₃). For solar radiation, the associated proportion values had a small fluctuation during the three periods. Overall, the responses of alpine grassland and alpine meadow ecosystems to climate change on the Qinghai-Tibet Plateau were increasing. The risk of grassland degradation on the Qinghai-Tibet Plateau might exacerbate due to the climate change with a large variability on the Qinghai-Tibet Plateau. This study aims to provide a reference for the dynamic assessment of ecosystem sensitivity on the Qinghai-Tibet Plateau in the context of global climate change.