Ecological Quality Variation of Vegetation on the Tibetan Plateau from 2001 to 2020 and Its Relationship with Westerly-Monsoon Synergy

As a sensitive indicator of climate change, vegetation ecological quality on the Tibetan Plateau (TP) plays a crucial role in indicating environmental change. Based on the meteorological and ecological data on the TP from 2001 to 2020, we analyze the variations of different vegetation types and their relationship with atmospheric circulations. The results suggest that the overall ecological quality of vegetation on the TP shows an improvement trend. The ecological quality index (EQI) of sparse shrubs increases dramatically, while it of evergreen coniferous forests shows a decreasing trend. Warming is an important factor contributing to the EQI increase in the northeastern TP. Precipitation increase is not favorable to the EQI increase in the southwest of grasslands. Furthermore, the strengthening of the East Asian and South Asian summer monsoons is beneficial for the EQI increase of coniferous forests and evergreen broad-leaved forests. The remarkable warming and humidifying in deciduous broad-leaved forests, mixed forests, partial shrubs and evergreen broad-leaved forests, and the meridional water vapor transport in the central-southern TP, is conducive to EQI increase. Although the strengthening of the TP summer monsoon and westerly remarkably favors the EQI increase in grasslands and shrubs, the variations in meridional water vapor flux transport in the northeast area and the zonal water vapor flux transport in the west, results in the marked EQI decrease. Thus, the northeastern and western parts are the main areas of ecological quality degradation. The results can provide a basis for ecological restoration and protection, the development and utilization of climate resources on the TP.