Interplay between snow phenology and vegetation phenology in Alaska under climate change

Snow cover is one of the most important factors controlling Arctic ecosystems' microclimate and plant growth conditions in Arctic ecosystems. Climate change has impacted the timing and spatial variability of both snow cover, and worldwide vegetation phenology across the globe. However, the mechanisms by which snowpack factors regulate the onset of the growing season remain to be thoroughly investigated, particularly under varying climatic conditions and growth stages. In this study, we investigated the influence of snow characteristics on vegetation phenology across different growth stages. Specifically, we analyzed the spatiotemporal dynamics of vegetation and snow phenology in Alaska from 2001 to 2021, assessed the partial correlations between key phenological groups under controlled temperature and precipitation conditions, and quantified the contributions of climatic variables and snow cover to vegetation phenology across various growth-cycle phases. The results revealed that grassland and forest phenology responded strongly to variations in snowmelt timing (r > 0.5, p < 0.05). In contrast, although phenological responses in wetlands were also statistically significant (p < 0.05), the average correlation was weaker (mean r ≈ 0.45). Temperature was found to be the primary driver of vegetation phenology change during the peak growth periods, whereas snow temperature and depth were crucial drivers during the transitional growth phases. From 2001 to 2021, the changes in vegetation phenology in Alaska were more pronounced than those in snow dynamics. Notwithstanding the significant role of other co-varying drivers of vegetation-phenological shifts, the influence of snow phenology was crucial. This study elucidates the role of snowpack phenology in regulating vegetation dynamics under changing climatic conditions and growth cycles.