Soil moisture drought and diverse impacts on vegetation across the Tibetan Plateau in recent three decades.

Abstract

Climate warming is presumed to cause drought on the Tibetan Plateau (TP), posing severe threats to local vegetation and ecosystems. Currently, soil moisture (SM) drought and its effects on vegetation growth have been rarely reported, due to lacking observations and data uncertainties. Here we used ERA5-Land, ESA CCI, and GLDAS Noah SM to investigate the spatiotemporal patterns of summertime (May-September) SM drought and its impacts on vegetation over 1995-2018. A total of 98, 82, and 86 SM drought events were identified based on the three products, respectively, ∼90 % of which coincided with meteorological water deficit. About 80 % of these events are less severe with a drought duration<2 months and a drought area <∼0.3 × 10⁶ km² (12 % of the TP). Drought severity shows an annual decreasing trend. Spatially, more droughts are found in humid, subhumid, and semiarid regions. Around 60 % of drought events cause adverse impacts on vegetation growth, mainly in arid, semiarid, and subhumid regions. Meadows and steppes are susceptible to drought with a high drought response rate (i.e. percentage of drought with vegetation damage) (>60 %) and a short time lag (<2 months), particularly for the case of meadows. However, large forests in humid regions are insensitive to SM droughts with a low response rate (<40 %) and a long time lag (1-3 months). The findings further the understanding of the diverse impacts of SM drought on vegetation growth across the TP, serving as an important implication for future ecological and environmental protection.