Spatiotemporal patterns of cumulative and lagged drought effects on vegetation dynamics across China

Study region China spans strong hydroclimatic gradients, from humid subtropical ecosystems in the southeast to arid and semi-arid ecosystems in the northwest and cold alpine ecosystems on the Qinghai-Tibet Plateau. We analyzed six major terrestrial ecological zones. Study focus A major challenge is to determine whether vegetation variability is more strongly associated with multimonth accumulated water balance or with antecedent monthly drought conditions across heterogeneous climates and vegetation types. We combined precipitation- and potential-evapotranspiration-derived SPEI at 1–12-month scales with MODIS NDVI, LAI, and GPP from 2001 to 2020. Pixel-wise Pearson correlations identified optimal cumulative and lagged timescales; ∆ R max quantified their relative dominance, which was further evaluated across ecological zones, a continuous long-term mean SPEI_12 gradient, and major vegetation types. New hydrological insights for the region Lag-dominant associations covered 61–68% of vegetated China and were concentrated in northern and northwestern regions, whereas cumulative-dominant associations prevailed in humid southeastern China. Cumulative timescales showed an inverted-U relationship and lagged timescales showed a U-shaped response along the long-term mean SPEI_12 gradient, with the longest cumulative integration occurring at intermediate SPEI conditions. Shrublands were predominantly cumulative-dominant (78.3–97.7%), whereas grasslands and croplands were predominantly lag-dominant (67.3–85.7%). These results reveal that vegetation-water-balance coupling is strongly region- and vegetation-type dependent and provide region-specific timescale information for drought monitoring and ecohydrological modeling.