Temporal evolution of soil drought stress and its relationship with climate change for tea plantations in the subtropical–warm temperate climate transition zone of China

Tea (Camellia sinensis (L.) Kuntze) plantation represents one of the most important artificial vegetation types in the subtropical–warm temperate climate transition zone of China. Soil drought stress is an important factor limiting the growth of tea plantation, but its long-term evolution characteristics and relationship with climate change have yet to be quantitatively analyzed. In this study, we employed the Biome-BGCMuSo model to simulate ecohydrological dynamics over the past 60 years (1961–2020) for tea plantations in the climate transition zone. The long-term evolution of soil drought stress was analyzed based on the annual and seasonal average soil drought stress index (AveSDSI). The relationships between the interannual trends and fluctuations of AveSDSI with climate factors were further examined through factorial simulations and partial correlation analysis, respectively. The results indicated the Biome-BGCMuSo model effectively simulated the soil moisture dynamics in tea plantations in the study area. From 1961–2020, annual and seasonal AveSDSI both exhibited increasing trends, with a significant linear relationship between spring AveSDSI and time. The 11-year moving standard deviation of both annual and spring AveSDSI showed significant increasing trends, indicating intensified interannual fluctuations in soil drought stress. Factorial simulations and partial correlation analysis revealed vapor pressure deficit (VPD) and precipitation were the primary factors influencing the interannual variability of AveSDSI, respectively dominating the interannual trend and fluctuation of annual AveSDSI. Notable seasonal differences were also evident. These findings provide an important foundation for optimizing management and disaster mitigation for tea plantations in the climate transition zone.