Permafrost affected soils are highly vulnerable to climate change. These soils store huge amounts of organic carbon (C), and a significant proportion of this carbon is stored in subsoil horizons where it might become available to microbial decomposition under global warming. An important factor in understanding and quantifying the C release from soils include the limitation of resources for microbes. Microbes decompose soil organic matter (SOM) by secreting extracellular enzymes into the soil, thus enzyme activity and their ratios are considered important indicators of soil nutrient availability and microbial substrate limitation. To evaluate nutrient limitation and the limitation of microbial substrate utilization, we investigated the potential enzyme activity from whole soil profiles, including topsoil, cryoturbated organic matter, mineral subsoil, and permafrost of Herschel Island (Canada) and Disko Island (Greenland). We included seven enzymes (five hydrolytic and two oxidative) and related them to bacterial and fungal gene abundance. The results showed hydrolytic enzymatic activity was strongly influenced by soil type, whereas oxidative enzymes varied between different localities. The enzyme ratios indicated that the topsoil microbial communities were C and phosphorus (P) co-limited in both localities, whereas the subsoil communities were nitrogen (N) limited from HI and C, P limited from DI. A strong positive correlation between all measured enzymes and bacterial gene abundance compared to that of fungi suggested that bacteria might play a more important role in SOM decomposition in permafrost soil horizons. This study suggests that Arctic permafrost microbial communities were not only limited by N, but also by C, P, and their co-limitation under specific conditions (i.e., higher abundance of bacteria and lower abundance of fungi).

受永久冻土影响的土壤极易受到气候变化的影响。这些土壤储存了大量的有机碳 (C)，其中很大一部分碳储存在地下层中，在全球变暖的情况下可能会被微生物分解。理解和量化土壤中碳释放的一个重要因素包括微生物资源的限制。微生物通过将细胞外酶分泌到土壤中来分解土壤有机质（SOM），因此酶活性及其比率被认为是土壤养分有效性和微生物底物限制的重要指标。为了评估养分限制和微生物底物利用的限制，我们研究了整个土壤剖面的潜在酶活性，包括表土、冷冻有机物、赫歇尔岛（加拿大）和迪斯科岛（格陵兰）的矿物底土和永久冻土。我们包括七种酶（五种水解酶和两种氧化酶）并将它们与细菌和真菌基因丰度相关联。结果表明，水解酶活性受土壤类型的强烈影响，而氧化酶在不同地区之间存在差异。酶比表明，两地表层土壤微生物群落为碳和磷（P）共同限制，而底土微生物群落为氮（N）限制于HI和C，P限制于DI。与真菌相比，所有测量的酶和细菌基因丰度之间存在强正相关，这表明细菌可能在多年冻土层的 SOM 分解中发挥更重要的作用。