Ridgeway Joanna R, Goldsmith Sarah B, Hicks Pries Caitlin E
Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire, USA.
Glob Chang Biol. 2025 Aug;31(8):e70405. doi: 10.1111/gcb.70405.
Winter climate change is outpacing our conceptual understanding of how winter conditions regulate soil biogeochemical cycling and ultimately impact vital ecosystem services like soil carbon and nutrient retention. In seasonally snow-covered ecosystems like northern temperate forests, increasingly inconsistent winters lead to less precipitation falling as snow, frequent midwinter snow melting, and the loss of a stable, insulative snowpack. These changes leave soils vulnerable to freezing, freeze/thaw cycling, and increasing dry/wet cycles from added snowmelt and rainwater. To uncover how these new winter soil climate conditions alter soil biogeochemistry, we introduce the DeFR❆ST (Determining Forest Responses to Snowmelt Treatments) experiment, a novel approach where we melt snow in situ throughout the winter and monitor changes to soil climate, gas exchange, and biogeochemical cycling. We installed DeFR❆ST in a New England temperate forest, an ecosystem that is part of the most significant global carbon sink and is also in the epicenter of winter climate change in the US. Experimental snow melting drove soil moisture fluctuations in addition to deep and persistent soil freezing. In turn, soils in melted plots exhibited blocked gas diffusion and lower soil oxygen availability. Oxygen limitation may have driven shifts in soil processes from high redox potential metabolisms like aerobic decomposition and nutrient mineralization towards low redox potential metabolisms like iron reduction and the dissolution of iron and carbon from organo-mineral associations. As these changes snowball, altered soil properties and shifts in soil microbial community structure and function could reshape forest biogeochemical cycling, both in these forests and more broadly across seasonally snow-covered ecosystems.
冬季气候变化正超出我们对冬季条件如何调节土壤生物地球化学循环以及最终如何影响诸如土壤碳和养分保持等重要生态系统服务的概念理解。在诸如北方温带森林这样季节性积雪的生态系统中，冬季越来越不稳定，导致以降雪形式出现的降水量减少、冬季中期频繁融雪以及稳定的隔热积雪层消失。这些变化使土壤容易受到冻结、冻融循环以及因融雪和雨水增加而导致的干湿循环加剧的影响。为了揭示这些新的冬季土壤气候条件如何改变土壤生物地球化学，我们引入了DeFR❆ST（确定森林对融雪处理的响应）实验，这是一种新颖的方法，我们在整个冬季对雪进行原位融化，并监测土壤气候、气体交换和生物地球化学循环的变化。我们在美国新英格兰温带森林中设置了DeFR❆ST，该生态系统是全球最重要的碳汇之一的一部分，也是美国冬季气候变化的中心地带。除了深层和持续的土壤冻结外，实验性融雪还导致了土壤湿度波动。反过来，融化区域的土壤表现出气体扩散受阻和土壤氧气可用性降低。氧气限制可能促使土壤过程从高氧化还原电位的代谢（如有氧分解和养分矿化）转向低氧化还原电位的代谢（如铁还原以及从有机矿物结合体中溶解铁和碳）。随着这些变化的不断累积，土壤性质的改变以及土壤微生物群落结构和功能的变化可能会重塑这些森林以及更广泛的季节性积雪生态系统中的森林生物地球化学循环。
