Climate change induced mild and rainy winters may expose soils to more frequent and prolonged waterlogging in boreal regions. Resulting oxygen depletion induces reductive dissolution of iron (Fe) oxides further altering the stability of Fe-associated organic matter. Thus far, the impact of waterlogging on the coupled cycling of Fe and carbon (C) in upland arable soils remains unknown. We constructed a monolithic experimental system with 32 soil profiles (l = 63 cm, d = 15.2 cm) collected from two agricultural fields (silty clay, sandy loam) to study the effects of off-season waterlogging, overwintering cover crop and soil type on soil redox potential (Eh), Fe solubility, and movement of C and nitrogen (N) within the soil–plant-atmosphere continuum. Soil moisture, temperature, electrical conductivity, and Eh were continuously monitored, and soil pore water samples were collected at three soil depths. Here, we assess the systems suitability for studying coupled Fe and C dynamics in boreal climate, and investigate the treatment impacts on soil Eh, pH, reductive Fe dissolution and N concentration in pore water. Waterlogging led to reducing conditions in both soils down to 30 cm depth at the soil temperature (+4 to 12 °C) matching those of spring and autumn in southern Finland. The declining Eh and the slightly rising Fe concentration in porewater (max ∼ 10 µmol l−1) suggest that reductive dissolution of Fe could proceed even during mild winters if the duration of waterlogging exceeds 1–2 weeks. The study demonstrated that cover crops may accelerate the drop in soil Eh by removing bioavailable N, and hence controlling the availability of alternative electron acceptors (nitrate) in the soil. Thus, the simultaneous effects of cover crops on C inputs, and on N and water dynamics, all influencing redox reactions, emphasize the importance of incorporating vegetation into studies exploring the impacts of waterlogging on coupled dynamics of Fe and C.

中文翻译：

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用于研究内涝对氧化还原过程影响的受控土壤整体实验


气候变化引起的温和多雨的冬季可能会使北方地区的土壤遭受更频繁和更长时间的内涝。由此产生的氧消耗诱导铁 （Fe） 氧化物的还原溶解，进一步改变了 Fe 伴生有机物的稳定性。到目前为止，内涝对陆地耕地土壤中 Fe 和碳 （C） 耦合循环的影响仍然未知。我们构建了一个整体实验系统，其中包含从两块农田（粉质粘土、沙壤土）收集的 32 个土壤剖面 （l = 63 cm， d = 15.2 cm），以研究淡季内涝、越冬覆盖作物和土壤类型对土壤氧化还原电位 （Eh）、Fe 溶解度以及土壤-植物-大气连续体中 C 和氮 （N） 的运动的影响。连续监测土壤水分、温度、电导率和 Eh，并在 3 个土壤深度收集土壤孔隙水样品。在这里，我们评估了系统是否适合研究北方气候中 Fe 和 C 耦合动力学，并研究了处理对土壤 Eh、pH 值、还原性 Fe 溶解和孔隙水中 N 浓度的影响。在土壤温度（+4 至 12 °C）下，涝涝导致两种土壤的状况降低至 30 厘米深，与芬兰南部的春季和秋季相当。Eh 的下降和孔隙水中 Fe 浓度略有上升（最大 ∼ 10 μmol l-1）表明，如果涝渍持续时间超过 1-2 周，即使在温和的冬季，Fe 的还原溶解也可以进行。研究表明，覆盖作物可以通过去除生物可利用的氮来加速土壤 Eh 的下降，从而控制土壤中替代电子受体（硝酸盐）的可用性。 因此，覆盖作物对 C 输入以及 N 和水动力学的同步影响，都影响氧化还原反应，强调了将植被纳入探索涝渍对 Fe 和 C 耦合动力学影响的研究的重要性。