干热复合事件对北半球植被的影响及时滞效应

As global climate change continues, the frequency and intensity of compound dry-heat events have significantly increased on both global and regional scales, exerting notable impacts on vegetation physiological activities. However, current studies mostly focus on the impacts of individual drought or heat events on vegetation while often neglecting the stress from compound dry-heat events. This study utilized monthly Standardized Precipitation Index (SPI), Standardized Temperature Index (STI), Compound Drought and Heat Index (CDHI), and Normalized Difference Vegetation Index (NDVI) from 1982 to 2015 to investigate the impacts and time-lag effects of different climatic conditions on vegetation during the growing season. The results revealed the following: (1) Compound dry-heat conditions generally promote vegetation growth at higher latitudes but suppresses it at mid-to-low latitudes. Additionally, as humidity increases, the effect of compound dry-heat conditions on vegetation shifts from suppression to promotion. Regarding different vegetation types, compound dry-heat conditions generally inhibit herbaceous plants while promoting woody plants. (2) The average lagged time of compound dry-heat and heat conditions events on vegetation is relatively short (1.1±1.8 and 1.1±1.9 months, respectively), whereas drought conditions exhibit a longer lagged time (2.8± 2.1 months). The lagged time of all events varies with humidity levels. However, in different extreme climate events, the lagged time of compound dry-heat events is longer and comparable to that of drought events, while heat events have a relatively short lagged time, with no significant variation across different climate zones. In summary, this study comprehensively analyzes the impact of different climatic conditions on vegetation and their time-lag effects, providing a scientific basis for understanding vegetation dynamics under climate change.