We investigated rates and controls on greenhouse gas (CO₂ and CH₄) production in two contrasting water‐saturated tundra soils within a permafrost‐affected watershed near Nome, Alaska, United States. Three years of field sample analysis have shown that soil from a fen‐like area in the toeslope of the watershed had higher pH and higher porewater ion concentrations than soil collected from a bog‐like peat plateau at the top of the hillslope. The influence of these contrasting geochemical and topographic environments on CO₂ and CH₄ production was tested in soil microcosms by incubating both the organic‐ and mineral‐layer soils anaerobically for 55 days. Nitrogen (as NH₄Cl) was added to half of the microcosms to test potential effects of N limitation on microbial greenhouse gas production. We found that the organic toeslope soils produced more CO₂ and CH₄, fueled by higher pH and higher concentrations of water‐extractable organic C (WEOC). Our results also indicate N limitation on CO₂ production in the peat plateau soils but not the toeslope soils. Together these results suggest that the weathering and leaching of ions and nutrients from tundra hillslopes can increase the rate of anaerobic soil organic matter decomposition in downslope soils by (1) increasing the pH of soil porewater; (2) providing bioavailable WEOC and fermentation products such as acetate; and (3) relieving microbial N limitation through nutrient runoff. We conclude that the soil geochemistry as mediated by landscape position is an important factor influencing the rate and magnitude of greenhouse gas production in tundra soils.

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山坡生物地球化学对苔原流域厌氧土壤有机质分解的影响

我们调查了在美国阿拉斯加诺姆附近受多年冻土影响的流域内两种形成对比的水饱和冻原土壤中温室气体（CO ₂和CH ₄）产生的速率和控制措施。三年的现场样本分析表明，与从山坡顶部的沼泽状泥炭高原收集的土壤相比，分水岭前坡的状区域的土壤具有较高的pH和较高的孔隙水离子浓度。通过将有机层和矿物层土壤厌氧孵育55天，在土壤微观环境中测试了这些相反的地球化学和地形环境对CO ₂和CH ₄产生的影响。氮（作为NH ₄将Cl）添加到一半的微观世界中，以测试氮限量对微生物温室气体产生的潜在影响。我们发现，由于较高的pH值和较高浓度的水萃取性有机碳（WEOC），有机草坡土​​壤产生了更多的CO ₂和CH ₄。我们的结果还表明N对CO _2的限制在泥炭高原土壤中生产，但在坡地土壤中没有。这些结果共同表明，苔原山坡上离子和养分的风化和浸出可以通过以下方式提高下坡土壤中厌氧性土壤有机质的分解速率：（1）提高土壤孔隙水的pH值；（2）提供可利用的WEOC和发酵产品，例如乙酸盐；（3）通过营养径流缓解微生物氮的限制。我们得出结论，由景观位置介导的土壤地球化学是影响苔原土壤中温室气体产生速率和幅度的重要因素。