The aim of this work was to assess the biogeochemical role of riparian soils in the High Arctic to determine to what extent these soils may act as sources or sinks of carbon (C) and nitrogen (N). To do so, we compared two riparian areas that varied in riparian vegetation coverage and soil physical perturbation (i.e., thermo‐erosion gully) in NE Greenland (74°N) during late summer. Microbial soil respiration (0.4–3.2 μmol CO2 m−2 s−1) was similar to values previously found across vegetation types in the same area and increased with higher temperatures, soil column depth and soil organic C degradation. Riparian soils had low nitrate concentrations (0.02–0.64 μg N‐NO3− g−1), negligible net nitrification rates and negative net N mineralization rates (−0.58 to 0.33 μg N g−1 day−1), thus indicating efficient microbial N uptake due to low N availability. We did not find any effects of physical perturbation on soil respiration or on N processing, but the dissolved fraction of organic matter in the soil was one order of magnitude lower on the disturbed site. Overall, our results suggest that riparian soils are small N sources to high‐Arctic streams and that a depleted dissolved organic C pool in disturbed soils may decrease exports to the adjacent streams under climate change projection.

中文翻译：

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高北极河岸土壤中的微生物碳和氮过程

这项工作的目的是评估高北极地区河岸土壤的生物地球化学作用，以确定这些土壤在多大程度上可以作为碳 (C) 和氮 (N) 的来源或汇。为此，我们比较了夏末格陵兰东北部 (74°N) 河岸植被覆盖率和土壤物理扰动（即热侵蚀沟壑）的两个河岸地区。微生物土壤呼吸（0.4-3.2 μmol CO2 m-2 s-1）与先前在同一地区的植被类型中发现的值相似，并且随着温度、土柱深度和土壤有机碳降解的增加而增加。河岸土壤的硝酸盐浓度低（0.02–0.64 μg N-NO3− g−1），净硝化率和负净氮矿化率（−0.58 到 0.33 μg N g−1 day−1）可忽略不计，因此表明微生物 N 有效由于 N 可用性低而吸收。我们没有发现物理扰动对土壤呼吸或氮处理的任何影响，但土壤中有机物质的溶解分数在受干扰的地点低一个数量级。总体而言，我们的结果表明，河岸土壤是高北极河流的小氮源，并且在气候变化预测下，受干扰土壤中溶解的有机碳库耗尽可能会减少对相邻河流的出口。