Identifying a strengthened vegetation sensitivity to drought and its potential drivers at sub-monthly temporal scale in Yangtze River Basin, China.

Abstract

Intensified droughts are recognized as a critical factor influencing vegetation productivity, yet many studies focus on monthly or longer temporal-resolution analysis, potentially overlooking short-term responses. Here, based on the constructed 8-day datasets over the past two decades, we employed correlation analysis to identify the vegetation sensitivity and response time to drought, and further investigated the underlying mechanisms of response differences across vegetation types using regression models. Our findings included: (i) Drought sensitivity (R_max = 0.6348) was stronger than earlier monthly studies, especially in the central Yangtze River Basin (YRB). Vegetation in Tanggula and Wuyi Mountains responded more rapidly, within 24 days. (ii) Cropland exhibited highest drought sensitivity (R_max = 0.6559) and grassland responded fastest (21.20∗8 day intervals); (iii) A drought sensitivity threshold (9.75-10) marked a turning point beyond which sensitivity declined, while response time generally shortened with increasing severity, except for cropland; (iv) Terrain played a relatively minor role in shaping vegetation response, whereas the impact of climate varied among vegetation types: croplands relied less on precipitation due to irrigation, forests were mainly influenced by precipitation, and alpine grasslands were strongly driven by solar radiation. Our study provided new insights into vegetation dynamics underpinned by drought at finer temporal resolution, highlighting the need to prioritize areas prone to drought impacts in future vegetation management practices.