Bergman Oded, Walter Anthony Katey, Eliani-Russak E, Sivan Orit
Department of Earth and Environmental Sciences, Ben Gurion University of the Negev, Beersheva, Israel.
Water and Environmental Research Center, University Alaska Fairbanks, Fairbanks, Alaska, USA.
Glob Chang Biol. 2025 Jul;31(7):e70356. doi: 10.1111/gcb.70356.
Large carbon and nitrogen pools are disproportionately concentrated in the icy, Pleistocene-aged silt deposits of Arctic Yedoma permafrost. Upon thaw, these undergo microbial mineralization, releasing greenhouse gases (GHGs) including carbon dioxide (CO), methane (CH), and nitrous oxide (NO). Here, we present combined geochemical data with microbial function and community dynamics from deep (7-m) talik soil boreholes in water-unsaturated yedoma upland in interior Alaska. Our results reveal significant in situ seasonal shifts in microbial function, community composition, and diversity throughout the talik. Methanogenesis persisted in the deep talik year-round. Winter methanotrophy was negligible within and above the methanogenic zone, leading to elevated CH production and emission to the atmosphere. This is likely due to reduced microbial methanotrophic activity associated with lower temperatures and nitrogen availability. During summer, strong aerobic methanotrophy near the soil surface reduced CH emissions. Nitrate/nitrite-mediated anaerobic oxidation of methane (AOM) by both archaea (ANME-2d clade) and bacteria (NC10 phylum) occurred at and above the anoxic methanogenic zone, further offsetting CH production. In contrast to CH4 production potentials, which were higher in surface soils in winter compared to summer, we observed higher NO production potentials in summer compared to winter. Nitrous oxide concentrations peaked at 10 cm (7.2 μM) and 105 cm (6.7 μM) and were associated with denitrification; nitrogen-mediated AOM by Methanoperedens (ANME2d). In the summer only and within the top 1 m of soil, high expression of nitrogen-related genes (narG, norB, amoA, Annamox, and Feammox) indicated active redox dynamics, potentially providing nitrogen species for AOM. The potential NO production in summer may imply higher net GHG emissions from yedoma uplands as climate change leads to longer summers and warmer soils in the future.
大量的碳和氮库不成比例地集中在北极叶德马永久冻土带冰冷的更新世淤泥沉积物中。解冻后，这些沉积物会经历微生物矿化，释放包括二氧化碳（CO）、甲烷（CH）和一氧化二氮（NO）在内的温室气体（GHG）。在此，我们展示了来自阿拉斯加内陆水不饱和叶德马高地深（7米）的融区土壤钻孔的地球化学数据与微生物功能及群落动态的综合数据。我们的结果揭示了整个融区微生物功能、群落组成和多样性显著的原位季节性变化。产甲烷作用全年在深层融区持续存在。在产甲烷带及其上方，冬季甲烷氧化作用可忽略不计，导致甲烷产量增加并排放到大气中。这可能是由于与较低温度和氮有效性相关的微生物甲烷氧化活性降低所致。在夏季，土壤表层附近强烈的好氧甲烷氧化作用减少了甲烷排放。在缺氧产甲烷带及其上方，古菌（ANME - 2d分支）和细菌（NC10门）通过硝酸盐/亚硝酸盐介导的甲烷厌氧氧化（AOM）发生，进一步抵消了甲烷的产生。与冬季相比，冬季表层土壤中产甲烷潜力更高，而与甲烷产生潜力相反，我们观察到夏季的一氧化二氮产生潜力高于冬季。一氧化二氮浓度在10厘米（7.2微摩尔）和105厘米（6.7微摩尔）处达到峰值，与反硝化作用有关；由甲烷食甲基菌（ANME2d）介导的氮介导的AOM。仅在夏季且在土壤表层1米范围内，与氮相关基因（narG、norB、amoA、厌氧氨氧化和铁氨氧化）的高表达表明活跃的氧化还原动态，可能为AOM提供氮物种。夏季一氧化二氮的潜在产生可能意味着随着气候变化导致未来夏季更长且土壤更温暖，叶德马高地的温室气体净排放量更高。
