Late spring frost delays tree spring phenology by reducing photosynthetic productivity

Under climate warming, earlier spring phenology has heightened the risk of late spring frost (LSF) damage. However, the intricate interplay among LSF, spring phenology and photosynthetic carbon uptake remains poorly understood. Using 286,000 ground phenological records involving 870 tree species and remote-sensing data across the Northern Hemisphere, we show that LSF occurrence in a given year reduces photosynthetic productivity by 13.6%, resulting in a delay in spring phenology by ~7.0 days in the subsequent year. Our experimental evidence, along with simulations using modified process-based phenology models, further supports this finding. This frost-induced delay in spring phenology subsequently leads to a decrease in photosynthetic productivity during the next year following an LSF event. Therefore, it is essential to integrate this frost-induced delay in spring phenology into current Earth system models to ensure accurate predictions of the impacts of climate extremes on terrestrial carbon cycling under future climate change. The authors use ground-based records and remote-sensing data to show that late spring frost delays the timing of spring leaf-out in the subsequent year by reducing photosynthetic productivity. Integrating late spring frost into models can increase the accuracy of predictions of spring timings and carbon cycling.