In the context of global warming and intensified human activity, understanding how meteorological drought (MD) propagates to agricultural drought (AD) across different soil depths is essential for improving agricultural production security. Focusing on Inner Mongolia (IM) as the research area, this study employed the standardized precipitation evapotranspiration index and standardized soil moisture index at various soil depths (swvl 1 -swvl 4 ) to represent MD and AD, respectively. The Copula function was applied to identify the non-linear propagation relationship between the MD and AD. Additionally, the Theil-Sen median, Mann-Kendall test, moving-window analysis, and wavelet analysis methods were integrated to reveal the spatiotemporal evolutionary trends of MD and AD and their propagation times (PT). Finally, a spatial causal relationship identification framework integrating Shapley Additive Explanations and Causal Forest was constructed to quantitatively assess the mechanisms influencing MD-AD drought PT across vegetation types. The results showed that MD and AD from swvl 1 to swvl 4 in the central and eastern IM both exhibited a trend of increasing severity, whereas the western region was primarily characterized by a trend toward humidification. The PT of MD and AD from the first to third layers (MD-AD swvl1–3 ) increased gradually with soil depth, and PT of less than six months primarily concentrated in central Xilingol, northern Hulunbuir, and the western IM. Northwest of Xilingol, MD-AD swvl4 exhibited a distinct distribution of shorter PT (< 6 months) than MD-AD swvl1–3 . Furthermore, in the desert steppe (DS) and sand land vegetation (SV) areas, MD-AD swvl1–2,4 had shorter PT and propagated more rapidly. The spatial extent and magnitude of the influence of human activity factors on MD-AD swvl1–4 were greater than those of meteorological factors. With respect to individual factors, CO₂, grazing intensity, potential evaporation, and temperature exhibited effects that prolonged PT in most vegetation types, while surface runoff and total precipitation delayed or shortened PT. However, in the DS and SV region, the direction of these effects shifted with soil depth. For MD-AD swvl1–2 and MD-AD swvl4 , all influencing factors prolonged the PT in BF and CNF and shortened the PT in DS and SV, respectively. The findings not only enhance the scientific understanding of drought evolution but also have practical implications for safeguarding agricultural and pastoral production and maintaining regional ecological balance. • The short propagation time of meteorological-agricultural drought varies regionally. • Shorter propagation times are observed both in humid forests and arid lands. • The propagation time trends shorten in desert steppe and sand land vegetation regions. • Human activity impacts propagation time (area, intensity) more than natural factors. • CO 2 and warming prolong propagation time, Runoff and Precipitation accelerate it.
Zhang et al. (Fri,) studied this question.