Biodiversity buffers the response of spring leaf unfolding to climate warming

Abstract

Abstract Understanding the sensitivity of spring leaf-out dates to temperature (ST) is integral to predicting phenological responses to climate warming and the consequences for global biogeochemical cycles. While variation in ST has been shown to be influenced by local climate adaptations, the impact of biodiversity on phenological sensitivity remains unknown despite its central role in ecosystem functioning. Here, we combine 393,139 forest inventory plots with satellite-derived ST across the Northern Hemisphere during 2001-2021 to show that biodiversity greatly affects spatial variation in ST and even surpasses the importance of climate variables. High tree diversity significantly weakened ST, possibly driven by both more diverse responses of leaf unfolding timing to warming directly, and indirect changes associated with root depth and soil biogeophysical and biogeochemical processes. We further show that current Earth System Models failed to reproduce the observed negative correlation between ST and biodiversity, with important implications for phenological responses under future emission pathways. Our results highlight the need to incorporate the buffering effects of biodiversity to better understand the impact of climate warming on spring leaf unfolding and carbon uptake in terrestrial ecosystems.