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首页> 外文期刊>Chemical geology >Multi-proxy study of soil organic matter dynamics in permafrost peat deposits reveal vulnerability to climate change in the European Russian Arctic
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Multi-proxy study of soil organic matter dynamics in permafrost peat deposits reveal vulnerability to climate change in the European Russian Arctic

机译：多年冻土泥炭沉积物中土壤有机物动力学的多代理研究表明，欧洲俄罗斯北极地区易受气候变化的影响

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Soil organic carbon (SOC) in permafrost terrain is vulnerable to climate change. Perennially frozen peat deposits store large amounts of SOC, but we know little about its chemical composition and lability.We used plant macrofossil and biomarker analyses to reconstruct the Holocene paleovegetation and paleoenvironmental changes in two peat plateau profiles fromthe European Russian Arctic. Peat plateaus are the main stores of permafrost soil C in the region, but duringmost of the Holocene peats developed as permafrost-free rich fens with woody vegetation, sedges andmosses. Around 2200 cal BP, permafrost aggraded at the site resulting in frost heave and a drastic reduction in peat accumulation under the drier uplifted surface conditions. The permafrost dynamics (aggradation, frost-heave and thaw) ushered changes in plant assemblages and carbon accumulation, and consequently in the biomarker trends too. Detailed biomarker analyses indicate abundant neutral lipids, which follow the general pattern: n-alkanols N sterols ≥ n-alkanes ≥ triterpenols. The lignin monomers are not as abundant as the lipids and increase with depth. The selected aliphatic and phenolic compounds are source specific, and they have different degrees of lability, which is useful for tracing the impact of permafrost dynamics (peat accumulation and/or decay associated with thawing). However, common interpretation of biomarker patterns, and perceived hydrological and climate changes, must be applied carefully in permafrost regions. The increased proportion (selective preservation) of n-alkanes and lignin is a robust indicator of cumulative decomposition trajectories, which is mirrored by functional compounds (e.g. n-alkanol, triterpenol, and sterol concentrations) showing opposite trends. The distribution of these compounds follows first order decay kinetics, and concurswith the downcore diagenetic changes. In particular, some of the biomarker ratios (e.g. stanol/sterol and higher plant alkane index) seem promising for tracing SOC decomposition despite changes in botanical imprint, and sites spanning across different soil types and locations. Carbon accumulation rate calculated at these sites varies from 18.1 to 31.1 gC m~(?2) yr~(?1), and it's evident selective preservation, molecular complexity of organic compounds, and freezing conditions enhance the long-term stability of SOC. Further, our results suggest that permafrost dynamics strongly impact the more undecomposed SOC that could be rapidly remobilized through ongoing thermokarst expansion.
机译：多年冻土地区的土壤有机碳（SOC）易受气候变化的影响。多年冻的泥炭沉积物储存了大量的SOC，但对其化学组成和不稳定性知之甚少。我们使用植物大化石和生物标记分析来重建欧洲俄罗斯北极地区两个泥炭高原剖面的全新世古植被和古环境变化。泥炭高原是该地区多年冻土C的主要储藏地，但是在全新世泥炭的大部分时期，它们都是无多年冻土的丰富的类，具有木本植物，莎草和苔藓。在2200 cal BP附近，永久冻土在该地点聚集，导致霜冻隆起，并且在干燥的地面条件下泥炭堆积急剧减少。多年冻土的动力学（凝结，霜冻和融化）带来了植物组合和碳积累的变化，因此也标志着生物标志物的发展。详细的生物标记分析表明，中性脂质含量很高，遵循以下一般模式：正构烷醇N固醇≥正构烷烃≥三萜醇。木质素单体不如脂质丰富，并随深度增加。所选的脂肪族和酚类化合物是特定于来源的，并且它们具有不同程度的不稳定性，这对于追踪多年冻土动力学的影响（与解冻有关的豌豆积累和/或腐烂）很有用。但是，在永久冻土地区，必须谨慎地应用生物标志物模式的常见解释以及感知的水文和气候变化。正构烷烃和木质素比例的增加（选择性保存）是累积分解轨迹的有力指标，这反映了显示相反趋势的功能化合物（例如正构烷醇，三萜醇和固醇浓度）。这些化合物的分布遵循一级衰减动力学，并与下层成岩作用一致。尤其是，尽管植物印记发生了变化，并且站点跨越不同土壤类型和位置，但某些生物标志物比率（例如，甾烷醇/固醇和较高的植物烷烃指数）似乎有望追踪SOC分解。在这些位置计算出的碳积累速率在18.1至31.1 gC m〜（？2）yr〜（？1）之间变化，明显的选择性保存，有机化合物的分子复杂性和冻结条件提高了SOC的长期稳定性。此外，我们的结果表明，多年冻土的动力学强烈影响了未分解的SOC，而SOC可以通过持续的热岩溶扩展而迅速恢复。

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