Complex interactions of "water-light-heat" climatic conditions on spring phenology in the mid-high latitudes of the Northern Hemisphere

Abstract

The mid-high latitudes of the Northern Hemisphere are one of the major gathering areas of global vegetation, playing a key role in regulating the climate and carbon cycle. Studying the interactive effects of vegetation phenological dynamics and climate change will help predict future vegetation dynamics and ecological protection. However, the response of vegetation phenology to multi-dimensional climatic factors is still unclear, and the spatiotemporal heterogeneity of their contributions to phenological changes and the complex interactions between them are not yet determined. This study used the solar-induced chlorophyll fluorescence (SIF) to invert accurate spring phenological parameters, and combined ERA5-Land datasets to obtain "water-light-heat" multi-dimensional climatic factors. We quantified the responses of the start of the growing season (SOS) to climate factors and the contributions and spatiotemporal heterogeneity of climate impacts, and discovered the complex relationships and influences. The results show that SOS predominantly occurred between 140-160 days during 2001–2020. SOS was slowly delayed until 2009, and then advanced before that. The climate sensitivity of SOS has obvious spatial differences, and different gradient levels of climate factors significantly affect the sensitivity of SOS. Furthermore, temperature, precipitation, and solar radiation are the dominant factors affecting SOS. Their contributions to SOS changes show obvious latitude patterns, with relative contributions and dominant areas varying across different sub-periods, but temperature consistently controlled the most area of SOS changes. This study reveals the complex interactions and mechanisms between climate change and spring phenology of vegetation on a large scale, aiding in predicting and addressing potential future ecological changes.