Root-zone moisture governs vegetation recovery after drought across the Mongolian plateau

Drought is intensifying across dryland ecosystems under climate change, yet the mechanisms controlling post-drought recovery remain unresolved. Satellite observations have produced conflicting evidence on whether photosynthetic activity or canopy greenness recovers first, limiting assessments of ecosystem resilience. Here we analyse 24 years of drought-recovery events across approximately 73,000 grassland pixels of the Mongolian Plateau, using GOSIF and GPP as functional indicators and NDVI and EVI as structural greenness indicators, to test how recovery varies with aridity and soil-water replenishment depth. After screening near-zero fluorescence baselines, canopy greenness and photosynthetic function recovered at broadly similar times, with remaining GOSIF–NDVI differences close to one native GOSIF observation interval. A large apparent driest-quartile reversal, in which greenness appeared to recover approximately 80 days before fluorescence, was predominantly a metric artifact: 57% of driest-quartile fluorescence events had near-zero baselines, and screening collapsed the difference from +80 to +8 days. Root-zone moisture was consistently associated with shorter GOSIF recovery, and this relationship remained consistent in separate tests using SPEI-based drought termination and spatial blocks up to 4°. GPP showed the same directional relationship but with weaker attribution magnitude under independent termination, whereas structural deep-soil coefficients and the aridity-specific recovery ordering were sensitive to the event-termination definition. These results identify a robust GOSIF–root-zone association while showing that broader functional–structural contrasts depend on event definition and spatial scale.