Satellite-observed solar-induced chlorophyll fluorescence reveals higher sensitivity of alpine ecosystems to snow cover on the Tibetan Plateau

Snow cover, which has been declining over recent decades because of rising temperatures, impacts alpine vegetation in various ways on the Tibetan Plateau (TP). However, it is still unclear how the alpine ecosystem responses to the rapid changes of snow cover on the TP. Here, we use the novel spaceborne measurements of solar-induced fluorescence (SIF) from the GOME-2 instrument, a direct proxy of photosynthetic activity, along with traditional vegetation indices (VIs) to study the responses of an alpine ecosystem to changes in snow cover over the TP. We find that seasonal dynamics of SIF are more consistent with alpine vegetation gross primary productivity (GPP) than those of enhanced vegetation index (EVI), suggesting the decoupling of photosynthesis and changes in greenness-based VIs. The snow cover explains most of the interannual variability of SIF, with secondary effects due to summer air temperature, while summer precipitation has little impact on alpine vegetation photosynthesis, indicating the critical role of snow cover in regulating alpine vegetation growth on the TP. This study suggests that the alpine vegetation photosynthesis on the TP is highly dependent on the snow cover at the start of the growing season and air temperature at the end of the growing season. Our results also demonstrate that the on-going satellite measurements of SIF shed new light on the understanding of future vegetation growth and vegetation-atmosphere interactions under a changing climate on the TP.