Time-Lagged and Cumulative Vegetation Responses to Climate Extremes and the Differential Contributions of Climatic and Non-Climatic Factors Across Coastal Mainland China

To investigate the temporal responses of vegetation to climate extremes and the drivers of vegetation change across coastal mainland China, this study analyzed monthly NDVI, meteorological, and land-cover data from 2000 to 2024. Spatiotemporal NDVI changes and the lagged and cumulative response windows for 15 climate indices were examined. Partial least squares regression and modified residual analysis were then used to estimate the contributions of climate change and non-climatic factors to NDVI trends. The results showed the following: (1) The multiyear mean NDVI was 0.772, and 83.15% of valid pixels exhibited an increasing trend, including 64.31% with a significant increase, with localized declines occurring in densely urbanized areas and some coastal plains. (2) Cumulative effects dominated the NDVI responses to climate indices, with a mean lag of 0.41 months and a mean cumulative window of 2.64 months. Response windows were generally shorter along the northern coast than along the southeastern and southern coasts. (3) Mean air temperature, monthly maximum of daily minimum air temperature, and diurnal temperature range had relatively high importance in the partial least squares model; the proportions of samples with VIP ≥ 1 were 80.28%, 72.77%, and 62.91%, respectively. (4) From 2000–2024, climatic factors contributed 0.001333 year−1 (33.78%) to the increasing annual-mean NDVI trend, while the non-climatic residual—not a direct estimate of human activity—contributed 0.002613 year−1 (66.22%). Temperature was the principal component of the regional climatic contribution, but the composition of contributions varied substantially among vegetation types and across latitude and longitude bands.