Spatiotemporal characteristics of soil drought and identification of influencing factors in various regions of China

As the evaporation capacity of land has increased, soil drought characterized by soil moisture deficiency directly threatens national food security and ecological security, and affects the sustainable development of the social economy. This study, based on the China region, utilized soil moisture datasets based on remote sensing and in-situ site observation data to assess the temporal evolution and spatial pattern of soil drought in China and its various regions from 2000 to 2022. It identified the main segmented locations, mutation types, and spatial trend characteristics of soil drought. The direct or indirect contributions of climatic factors and circulation factors to soil drought were identified. The results showed that: (1) During the study period, the minimum value (–0.81) of the original standardized soil moisture index (SSMI) sequence occurred in August 2004, and one positive breakpoint occurred in March 2010. Soil drought in China presented a changing trend of first aggravation and then deceleration. (2) There were mainly four types of mutations in soil drought: “interrupted decrease”, “interrupted increase”, “decrease to increase”, and “increase to decrease”, and most of the mutation points occurred after 2010. (3) The most severe soil drought occurred in 2009 (SSMI= –0.55), and the drought center was mainly located in the southern Yunnan-Guizhou Plateau Region (YPR) in autumn and winter. (4) The drought in each month and quarter in the Huang-Huai-Hai Plain Region (HPR) showed an increasing trend. (5) Based on cross-wavelet transform, the three best variables for explaining soil drought changes were soil moisture, precipitation, and evapotranspiration. This study reveals the regions in China where soil drought changes are more likely to occur, which can provide a scientific reference for revealing the formation mechanism of soil drought, as well as drought adaptation and response measures.