Understanding the sensitivity of spring leaf-out dates to temperature (S_T) is integral to predicting phenological responses to climate warming and the consequences for global biogeochemical cycles. While variation in S_T has been shown to be influenced by local climate adaptations, the impact of biodiversity remains unknown. Here we combine 393,139 forest inventory plots with satellite-derived S_T across the northern hemisphere during 2001–2022 to show that biodiversity greatly affects spatial variation in S_T and even surpasses the importance of climate variables. High tree diversity significantly weakened S_T, possibly driven by changes in root depth and soil processes. We show that current Earth system models fail to reproduce the observed negative correlation between S_T and biodiversity, with important implications for phenological responses under future 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.

了解春季落叶日期对温度 ( ST ₎的敏感性对于预测气候变暖的物候反应以及全球生物地球化学循环的后果至关重要。虽然S _T的变化已被证明受到当地气候适应的影响，但生物多样性的影响仍然未知。在这里，我们将 2001 年至 2022 年北半球的 393,139 个森林清查图与卫星来源的ST _T结合起来，表明生物多样性极大地影响了ST _T的空间变化，甚至超过了气候变量的重要性。高树木多样性显着削弱了S _T ，这可能是由根部深度和土壤过程的变化驱动的。我们表明，当前的地球系统模型无法重现观测到_的ST与生物多样性之间的负相关性，这对未来路径下的物候反应具有重要意义。我们的结果强调需要纳入生物多样性的缓冲效应，以更好地了解气候变暖对春季树叶展开和碳吸收的影响。