Freeze–thaw (FT) events exert a great physiological stress on the soil microbial community and thus significantly impact soil biogeochemical processes. Studies often show ambiguous and contradicting results, because a multitude of environmental factors affect biogeochemical responses to FT. Thus, a better understanding of the factors driving and regulating microbial responses to FT events is required. Soil chronosequences allow more focused comparisons among soils with initially similar start conditions. We therefore exposed four soils with contrasting organic carbon contents and opposing soil age (i.e., years after restoration) from a postmining agricultural chronosequence to three consecutive FT events and evaluated soil biochgeoemical responses after thawing. The major microbial biomass carbon losses occurred after the first FT event, while microbial biomass N decreased more steadily with subsequent FT cycles. This led to an immediate and lasting decoupling of microbial biomass carbon:nitrogen stoichiometry. After the first FT event, basal respiration and the metabolic quotient (i.e., respiration per microbial biomass unit) were above pre-freezing values and thereafter decreased with subsequent FT cycles, demonstrating initially high dissimilatory carbon losses and less and less microbial metabolic activity with each iterative FT cycle. As a consequence, dissolved organic carbon and total dissolved nitrogen increased in soil solution after the first FT event, while a substantial part of the liberated nitrogen was likely lost through gaseous emissions. Overall, high-carbon soils were more vulnerable to microbial biomass losses than low-carbon soils. Surprisingly, soil age explained more variation in soil chemical and microbial responses than soil organic carbon content. Further studies are needed to dissect the factors associated with soil age and its influence on soil biochemical responses to FT events.

冻融 (FT) 事件对土壤微生物群落施加巨大的生理压力，从而显着影响土壤生物地球化学过程。研究经常显示出模棱两可和相互矛盾的结果，因为多种环境因素会影响对 FT 的生物地球化学反应。因此，需要更好地了解驱动和调节微生物对 FT 事件反应的因素。土壤时间序列允许在初始条件相似的土壤之间进行更集中的比较。因此，我们暴露了四种土壤，其有机碳含量不同，土壤年龄（即恢复后的年数）从后农业时间序列到三个连续的 FT 事件，并评估解冻后土壤生物化学反应。主要的微生物生物量碳损失发生在第一次 FT 事件之后，而微生物生物量 N 随着随后的 FT 循环而更加稳定地下降。这导致微生物生物质碳：氮化学计量的直接和持久解耦。在第一次 FT 事件后，基础呼吸和代谢商数（即每个微生物生物量单位的呼吸）高于冷冻前的值，然后随着后续的 FT 循环而降低，表明最初的异化碳损失高，微生物代谢活动越来越少。迭代 FT 循环。因此，在第一次 FT 事件后，土壤溶液中溶解的有机碳和总溶解氮增加，而释放的大部分氮可能通过气体排放损失。总体而言，高碳土壤比低碳土壤更容易受到微生物生物量损失的影响。出奇，土壤年龄比土壤有机碳含量更能解释土壤化学和微生物反应的变化。需要进一步的研究来剖析与土壤年龄相关的因素及其对土壤生化反应对 FT 事件的影响。