Soil microbial communities regulate global biogeochemical cycles and respond rapidly to changing environmental conditions. However, understanding how soil microbial communities respond to climate change, and how this influences biogeochemical cycles, remains a major challenge. This is especially pertinent in alpine regions where climate change is taking place at double the rate of the global average, with large reductions in snow cover and earlier spring snowmelt expected as a consequence. Here, we show that spring snowmelt triggers an abrupt transition in the composition of soil microbial communities of alpine grassland that is closely linked to shifts in soil microbial functioning and biogeochemical pools and fluxes. Further, by experimentally manipulating snow cover we show that this abrupt seasonal transition in wide-ranging microbial and biogeochemical soil properties is advanced by earlier snowmelt. Preceding winter conditions did not change the processes that take place during snowmelt. Our findings emphasise the importance of seasonal dynamics for soil microbial communities and the biogeochemical cycles that they regulate. Moreover, our findings suggest that earlier spring snowmelt due to climate change will have far reaching consequences for microbial communities and nutrient cycling in these globally widespread alpine ecosystems.

土壤微生物群落调节全球生物地球化学循环并迅速响应不断变化的环境条件。然而，了解土壤微生物群落如何应对气候变化，以及这如何影响生物地球化学循环，仍然是一项重大挑战。这在高山地区尤为重要，那里的气候变化速度是全球平均速度的两倍，因此预计积雪将大量减少，春季融雪将提前。在这里，我们表明春季融雪引发了高寒草原土壤微生物群落组成的突然转变，这与土壤微生物功能和生物地球化学池和通量的变化密切相关。更远，通过实验操纵积雪，我们表明，早期融雪推动了广泛的微生物和生物地球化学土壤特性的这种突然的季节性转变。之前的冬季条件并没有改变融雪期间发生的过程。我们的研究结果强调了季节性动态对土壤微生物群落及其调节的生物地球化学循环的重要性。此外，我们的研究结果表明，由于气候变化导致的早春融雪将对这些全球分布的高山生态系统中的微生物群落和养分循环产生深远的影响。我们的研究结果强调了季节性动态对土壤微生物群落及其调节的生物地球化学循环的重要性。此外，我们的研究结果表明，由于气候变化导致的早春融雪将对这些全球分布的高山生态系统中的微生物群落和养分循环产生深远的影响。我们的研究结果强调了季节性动态对土壤微生物群落及其调节的生物地球化学循环的重要性。此外，我们的研究结果表明，由于气候变化导致的早春融雪将对这些全球分布的高山生态系统中的微生物群落和养分循环产生深远的影响。