Multiscale response of vegetation growth to climate extremes

In recent decades, the intensity and frequency of extreme climatic events have increased markedly, causing remarkable effects on terrestrial ecosystems. Understanding how these climate extreme climatic events affect vegetation growth is important for the global change ecology. We used vegetation index with satellite observations, including the normalised difference vegetation index (NDVI), enhanced vegetation index (EVI), and solar-induced chlorophyll fluorescence (SIF) to assess vegetation growth, and applied event coincidence analysis and sensitivity analysis to study how the climate extreme (extreme heat, cold, wet and drought) lead to abnormal vegetation growth in different areas. First, taking Northeast Asia as an example, our results show that extreme heat promotes vegetation growth, while extreme cold adversely affects vegetation growth. The beneficial effect of extreme heat on vegetation growth weakens with increasing temperature gradients, but amplifies with rising humidity gradients. This indicated that extreme heat is beneficial for vegetation growth in cold and humid regions. To further verify the above conclusions, we extended the study area to the Northern Hemisphere. In the Northern Hemisphere, extreme heat and cold are important climatic factors affecting the abnormal vegetation growth in the cold and humid ecosystems. Water-related extreme events were less influential to abnormal vegetation growth, mainly affecting relatively warm and arid ecosystems. In summary, our results emphasise the crucial role of background hydrothermal conditions in the attribution of vegetation growth extremes to diverse climate extremes.