Declining seasonal snow cover duration leads to changing conditions for plant recruitment and growth in temperate mountains. Yet capturing the intricacy of snow cover and vegetation dynamics at multidecadal scale in complex terrains poses a great challenge. Here we show that over the last four decades the greenness trend in European mountains increases with the annual date of the seasonal snow cover disappearance. By combining satellite data of high spatial resolution and downscaled climate re-analysis we show that the reduction in snow cover duration surpasses elevated temperatures in influencing heat accumulation during the growing season. This accumulation is a key driver of the pronounced greening observed in late snow-melting sites, particularly in sparsely vegetated, north-facing screes. Our results provide a comprehensive account of rapid vegetation changes in waning snowfields and highlight the pivotal role played by snow cover dynamics to unravel the complexity of greening within the temperate alpine zone.

季节性积雪持续时间的减少导致温带山区植物补充和生长的条件发生变化。然而，在复杂地形中以多年代际尺度捕捉积雪和植被动态的复杂性是一项巨大的挑战。在这里，我们表明，在过去的四十年中，欧洲山区的绿化趋势随着季节性积雪消失的年份而增加。通过结合高空间分辨率的卫星数据和缩小的气候再分析，我们表明，在影响生长季节热量积累方面，积雪持续时间的减少超过了高温。这种积累是在后期融雪地点观察到明显绿化的关键驱动因素，尤其是在植被稀疏、朝北的碎石中。我们的结果全面描述了逐渐减少的雪原中植被的快速变化，并强调了积雪覆盖动力学在揭示温带高山地区绿化复杂性方面发挥的关键作用。