Susceptibility of vegetation low-growth to climate extremes on Tibetan Plateau

Both intensity and frequency of climate extreme events have significantly increased over the past decades, which triggered exceptional responses in terrestrial ecosystems. Resolving the responses of vegetation growth to climate extremes are essential but challenging. The Tibetan Plateau (TP), home to fragile alpine ecosystems, is sensitive to increased climatic variabilities and thus an ideal region to characterize various ecosystem response to climate extremes. In this study, we employed event coincidence analysis to detect the susceptibility (quantified by coincidence rate) of vegetation low-growth to four climate extremes (drought, extreme wet, extreme hot and cold) using Normalized Difference Vegetation Index (NDVI) and solar-induced chlorophyll fluorescence (SIF) over TP for the period 2001 to 2018. We found notable changes in the susceptibility of vegetation low-growth to climate extremes along climate gradients, with higher susceptibility to extreme hot generally being found in warmer regions, while higher susceptibility to extreme cold in colder regions. Meanwhile, susceptibility to drought decreased while that to extreme wet increased with increasing precipitation. We also found higher susceptibility of herbaceous plants for drought and extreme hot than woody plants, but their susceptibility to extreme wet and cold was relatively lower. The varied vegetation susceptibility to climate extremes along climate gradient and among different vegetation types were due to the sensitivity of vegetation to climate variability, rather than the intensity or frequency of climate extremes. This study identified the ecological sensitive regions under climate extreme events, and highlighted the risk of decline in vegetation growth under warm-droughts in spite of a wetting climate over Tibetan Plateau.