Shifts in the trends of vegetation greenness and photosynthesis in different parts of Tibetan Plateau over the past two decades

Abstract

Ecosystems on the Tibetan Plateau (TP) are fragile and sensitive to climate change and thus provide insight into the climate regulations on vegetation structure and function. In this study, we utilized the Normalized Difference Vegetation Index (NDVI) and solar-induced chlorophyll fluorescence (SIF) to explore vegetation dynamics during the growing season from 2000 to 2021, and further investigated how climate change has influenced them. Based on both NDVI and SIF, significant vegetation greening trends were observed in northeastern TP across the study period due to continuous increases in both temperature and water availability. Browning trends were observed in southwestern TP due to decreasing precipitation and enhanced warming stress during 2000–2007, but the trends reversed after 2007. In the southeastern region, we also detected a turning point of a more prominent greening trend in 2016. Moreover, changes in SIF exhibited greater magnitude compared to NDVI, implying vegetation photosynthesis is more sensitive to climate change than greenness, potentially due to variations in light use efficiency. This study strengthens our understanding of climate regulations on vegetation structure and function under different hydrothermal conditions and highlights the need for additional research on the differences between greenness and photosynthesis.