Permafrost soils in the northern hemisphere are known to harbor large amounts of soil organic matter (SOM). Global climate warming endangers this stable soil organic carbon (SOC) pool by triggering permafrost thaw and deepening the active layer, while at the same time progressing soil formation. But depending, e.g., on ice content or drainage, conditions in the degraded permafrost can range from water-saturated/anoxic to dry/oxic, with concomitant shifts in SOM stabilizing mechanisms. In this field study in Interior Alaska, we investigated two sites featuring degraded permafrost, one water-saturated and the other well-drained, alongside a third site with intact permafrost. Soil aggregate- and density fractions highlighted that permafrost thaw promoted macroaggregate formation, amplified by the incorporation of particulate organic matter, in topsoils of both degradation sites, thus potentially counteracting a decrease in topsoil SOC induced by the permafrost thawing. However, the subsoils were found to store notably less SOC than the intact permafrost in all fractions of both degradation sites. Our investigations revealed up to net 75% smaller SOC storage in the upper 100 cm of degraded permafrost soils as compared to the intact one, predominantly related to the subsoils, while differences between soils of wet and dry degraded landscapes were minor. This study provides evidence that the consideration of different permafrost degradation landscapes and the employment of soil fractionation techniques is a useful combination to investigate soil development and SOM stabilization processes in this sensitive ecosystem.

众所周知，北半球的永久冻土含有大量的土壤有机质 (SOM)。全球气候变暖引发永久冻土融化并加深活性层，同时促进土壤形成，从而危及这种稳定的土壤有机碳（SOC）库。但根据含冰量或排水等情况，退化的永久冻土条件可能从水饱和/缺氧到干燥/缺氧，同时 SOM 稳定机制也会发生变化。在阿拉斯加内陆的这项实地研究中，我们调查了两个具有退化永久冻土的地点，一个水饱和的，另一个排水良好的，以及第三个具有完整永久冻土的地点。土壤团聚体和密度分数强调，永久冻土融化促进了大团聚体的形成，并通过颗粒有机物的掺入而放大了这两个退化地点的表土，从而可能抵消永久冻土融化引起的表土 SOC 的减少。然而，我们发现在两个退化地点的所有部分中，底土储存的 SOC 明显少于完整的永久冻土。我们的调查显示，与完整土壤相比，退化永冻土上部 100 厘米的 SOC 储存量减少了 75%，这主要与底土有关，而湿和干退化景观的土壤之间的差异很小。这项研究提供的证据表明，考虑不同的永久冻土退化景观和土壤分馏技术的使用是研究这一敏感生态系统中土壤发育和土壤有机质稳定过程的有用组合。