Spatiotemporal variations of extreme climate and their effects on vegetation growth in the northern permafrost regions during 1982–2022

The permafrost regions of the northern hemisphere are increasingly experiencing frequent and intense extreme climate, which may significantly impact the vegetation growth. However, the effects of extremes on vegetation are often overlooked, leading to an underestimation of their impacts on vegetation. Here we provide a comprehensive analysis of the spatiotemporal variations of extreme climate in the northern permafrost regions from 1982 to 2022, as well as the responses of vegetation growth to these changes in growing-seasons. The results show that: (1) the occurrence of warm days and nights increased, with nighttime temperature rises exceeding those during the day. The changing trend of extreme warm indices was less pronounced than that of extreme cold indices; (2) The frequency and duration of extreme precipitation had significantly increased, with slight changes in precipitation intensity; (3) The extreme temperature events largely showed no cumulative and lagged effects on vegetation growth, and the areas with one-month lag and two-month cumulative effects of extreme precipitation ranged from 19.1 % to 42.9 %; (4) The relationship between vegetation growth and extreme climate events varied by vegetation type. Grasslands, forests, and shrubs were mainly affected by the one-month lag and two-month cumulative effect of extreme precipitation, whereas wetlands exhibited a predominant one-month lag effect. Overall, our results suggested that the effects of extreme climate on vegetation growth in northern permafrost regions were mainly manifested by the cumulative and lagged effects of precipitation from 1982 to 2022, and more attentions should be paid to extreme precipitation in modelling vegetation growth under a changing climate in the permafrost regions.