Geosciences Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA.
Department of Earth System Science, Stanford University, Stanford, California, USA.
Glob Chang Biol. 2024 Jul;30(7):e17394. doi: 10.1111/gcb.17394.
Water-logged peatlands store tremendous amounts of soil carbon (C) globally, accumulating C over millennia. As peatlands become disturbed by human activity, these long-term C stores are getting destabilized and ultimately released as greenhouse gases that may exacerbate climate change. Oxidation of the dissolved organic carbon (DOC) mobilized from disturbed soils to streams and canals may be one avenue for the transfer of previously stored, millennia-aged C to the atmosphere. However, it remains unknown whether aged peat-derived DOC undergoes oxidation to carbon dioxide (CO) following disturbance. Here, we use a new approach to measure the radiocarbon content of CO produced from the oxidation of DOC in canals overlying peatland soils that have undergone widespread disturbance in Indonesia. This work shows for the first time that aged DOC mobilized from drained and burned peatland soils is susceptible to oxidation by both microbial respiration and photomineralization over aquatic travel times for DOC. The bulk radiocarbon age of CO produced during canal oxidation ranged from modern to ~1300 years before present. These ages for CO were most strongly influenced by canal water depth, which was proportional to the water table level where DOC is mobilized from disturbed soils to canals. Canal microbes preferentially respired older or younger organic C pools to CO, and this may have been facilitated by the use of a small particulate organic C pool over the dissolved pool. Given that high densities of canals are generally associated with lower water tables and higher fire risk, our findings suggest that peatland areas with high canal density may be a hotspot for the loss of aged C on the landscape. Taken together, the results of this study show how and why aquatic processing of organic C on the landscape can enhance the transfer of long-term peat C stores to the atmosphere following disturbance.
水饱和的泥炭地在全球范围内储存了大量的土壤碳 (C)，这些碳在地层中积累了数千年。随着泥炭地受到人类活动的干扰，这些长期储存的碳开始变得不稳定，并最终以温室气体的形式释放出来，从而可能加剧气候变化。从受干扰的土壤中迁移到溪流和运河中的溶解有机碳 (DOC) 的氧化可能是将先前储存的、数千年历史的碳转移到大气中的一种途径。然而，泥炭衍生的 DOC 在受到干扰后是否会氧化为二氧化碳 (CO) 仍然未知。在这里，我们使用一种新方法来测量源自印度尼西亚广泛干扰的泥炭地土壤上覆盖的运河中 DOC 氧化产生的 CO 的放射性碳含量。这项工作首次表明，从排水和燃烧的泥炭地土壤中迁移出来的老化 DOC 很容易被微生物呼吸和光矿化氧化，而 DOC 的水动力传输时间很短。在运河氧化过程中产生的 CO 的大量放射性碳年龄范围从现代到距今约 1300 年。CO 的这些年龄主要受运河水深的影响，而水深与从受干扰的土壤到运河迁移的地下水位成正比。运河中的微生物优先将较老或较年轻的有机碳库呼吸为 CO，这可能是由于较小的颗粒有机碳库而不是溶解有机碳库的使用。鉴于运河密度通常与地下水位较低和火灾风险较高相关，我们的研究结果表明，具有高密度运河的泥炭地地区可能是景观中老化碳损失的热点。总的来说，这项研究的结果表明了在景观上，有机碳的水相处理如何以及为何能增强干扰后长期泥炭碳储存向大气的转移。
