Department of Ecosystems Biology, University of South Bohemia in České Budějovice, Branišovská 31, 370 05 České Budějovice, Czech Republic.
Institute of Microbiology, University of Greifswald, Felix-Hausdorff-Str. 8 17487 Greifswald, Germany.
FEMS Microbiol Ecol. 2021 Mar 8;97(3). doi: 10.1093/femsec/fiab008.
Substantial amounts of topsoil organic matter (OM) in Arctic Cryosols have been translocated by the process of cryoturbation into deeper soil horizons (cryoOM), reducing its decomposition. Recent Arctic warming deepens the Cryosols´ active layer, making more topsoil and cryoOM carbon accessible for microbial transformation. To quantify bacteria, archaea and selected microbial groups (methanogens - mcrA gene and diazotrophs - nifH gene) and to investigate bacterial and archaeal diversity, we collected 83 soil samples from four different soil horizons of three distinct tundra types located in Qikiqtaruk (Hershel Island, Western Canada). In general, the abundance of bacteria and diazotrophs decreased from topsoil to permafrost, but not for cryoOM. No such difference was observed for archaea and methanogens. CryoOM was enriched with oligotrophic (slow-growing microorganism) taxa capable of recalcitrant OM degradation. We found distinct microbial patterns in each tundra type: topsoil from wet-polygonal tundra had the lowest abundance of bacteria and diazotrophs, but the highest abundance of methanogens. Wet-polygonal tundra, therefore, represented a hotspot for methanogenesis. Oligotrophic and copiotrophic (fast-growing microorganism) genera of methanogens and diazotrophs were distinctly distributed in topsoil and cryoOM, resulting in different rates of nitrogen flux into these horizons affecting OM vulnerability and potential CO2 and CH4 release.
大量北极永冻层土壤的有机质（OM）通过冻融作用转移到更深的土壤层（冻融 OM），从而减少了其分解。最近北极地区的变暖加深了永冻层土壤的活动层，使更多的表土和冻融 OM 碳更容易被微生物转化。为了定量分析细菌、古菌和选定的微生物类群（产甲烷菌 - mcrA 基因和固氮菌 - nifH 基因），并研究细菌和古菌的多样性，我们从位于 Qikiqtaruk（加拿大西部 Hershel 岛）的三种不同类型的苔原中采集了 83 个土壤样本，这些样本来自四个不同的土壤层。总的来说，从表土到永冻层，细菌和固氮菌的丰度减少，但冻融 OM 却没有减少。古菌和产甲烷菌没有观察到这种差异。冻融 OM 富含能够降解难降解 OM 的贫营养型（生长缓慢的微生物）类群。我们在每个苔原类型中都发现了独特的微生物模式：湿地多边形苔原的表土中细菌和固氮菌的丰度最低，但产甲烷菌的丰度最高。因此，湿地多边形苔原是产甲烷的热点。贫营养型和富营养型（生长迅速的微生物）产甲烷菌和固氮菌的属在表土和冻融 OM 中分布明显，导致氮通量进入这些层的不同速率，从而影响 OM 的脆弱性和潜在的 CO2 和 CH4 释放。
