LISAH, Univ Montpellier, INRAE, IRD, Institut Agro, 34060, Montpellier, France.
Department of Geography and Planning, Queen's University, Kingston, ON, K7L 3N6, Canada.
Nat Commun. 2020 Sep 9;11(1):4500. doi: 10.1038/s41467-020-18331-w.
Permafrost degradation may lead to mobilization of carbon and nutrients and enhance microbial processing rates of previously frozen organic matter. Although the pool size and chemical composition of dissolved organic matter (DOM) are fundamental determinants of the carbon cycle in Arctic watersheds, its source within the seasonally thawing active layer and the underlying permafrost remains largely uncharacterized. Here, we used 25 soil cores that extended down into the permafrost from nine sites across Arctic Canada to quantify dissolved organic carbon (DOC) and nitrogen stocks, and to characterize DOM optical properties. Organic permafrost stores 5-7 times more DOC and ammonium than the active layer and mineral permafrost. Furthermore, the permafrost layers contain substantial low molecular weight DOM with low aromaticity suggesting high biodegradability. We conclude that soil organic matter stoichiometry and cryogenic processes determine permafrost DOM chemistry, and that thawing will mobilize large amounts of labile DOC and ammonium into Arctic watersheds.
永久冻土的退化可能导致碳和养分的释放，并增强微生物对先前冻结的有机物质的处理速度。尽管溶解有机物质（DOM）的池大小和化学组成是北极流域碳循环的基本决定因素，但在季节性解冻的活动层和下面的永冻层内，其来源在很大程度上还没有得到描述。在这里，我们使用了 25 个从加拿大北极地区 9 个地点延伸到永冻层以下的土壤芯，以量化溶解有机碳（DOC）和氮储量，并对 DOM 的光学性质进行了表征。有机永冻土储存的 DOC 和铵比活动层和矿物永冻土多 5-7 倍。此外，永冻层含有大量低分子量、低芳香度的 DOM，表明其具有较高的生物降解性。我们的结论是，土壤有机质化学计量和低温过程决定了永冻土 DOM 的化学性质，并且解冻将大量可利用的 DOC 和铵释放到北极流域。
