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Effects of snow drought on spring green-up on the Mongolian Plateau
Snow drought has become a research hotspot due to its widespread impacts on ecosystems and water resources, yet its effects on vegetation phenology remain relatively understudied. Focusing on the Mongolian Plateau, this study used the Snow Water Equivalent Index and the start of growing season (SOS) to assess the associations between snow drought and vegetation green-up and their differences among vegetation types by integrating trend analysis, partial correlation analysis, lagged effect analysis, linear mixed-effects models, and structural equation modelling. Results show that snow drought significantly intensified during 1982–2022 (slope = 0.13, p < 0.05), with this trend predominantly occurring in the central and western Mongolian Plateau and exhibiting greater intensification in typical steppe and desert steppe. SOS advanced overall but exhibited strong spatial differentiation. Positive associations between snow drought and SOS were dominant in the northern and western regions, whereas negative associations were more concentrated in the eastern and southern margins. Relative to non-snow-drought conditions, SOS generally occurred later under snow drought conditions, with the largest difference of 9.49 days observed in desert steppe. Lagged effects were mainly identified for early spring of the current year, with April accounting for the largest proportion, while the sensitive months differed among vegetation types. Snow drought was independently associated with SOS and was also indirectly associated with SOS through soil-mediated hydrothermal pathways. These findings provide scientific support for regional snow drought monitoring and early warning, ecological risk assessment, and adaptive management.