Abstract

Management of drained peatlands may pose a risk or a solution on the way towards climate change mitigation, which creates a need to evaluate the current state of forestry-drained peatlands, the magnitude of degradation processes and indicators for carbon (C) loss. Using a large dataset (778 profiles, 891 peat samples, collected between 1977 and 2017) from peatlands having different fertility classes across Finland, we investigate whether the surface peat profiles of undrained and forestry-drained peatlands differ in C:N, von Post and dry bulk density. The utility of element ratios (C:N:H stoichiometry) as site indicators for degradation were further analyzed from a subsample of 16 undrained and 30 drained peat profiles. This subsample of drained sites had carbon dioxide (CO₂) and methane (CH₄) fluxes measured allowing us to link peat element ratios to annual C gas effluxes. Element ratios H:C, O:C and C:N and degree of unsaturation (combining C, N, H changes) were found widely valid: they captured both differences in the botanical origin of peat as well as its potential decomposition pathway (C lost via a combination of dissolved organic C and C gas loss and/or the gaseous loss predominantly as CO₂). Of the stoichiometric indexes, peat H:C ratio seemed to be the best proxy for degradation following drainage, it indicated not only long-term degradation but also explained 48% of the variation in annual CO₂ emission. The O:C ratio positively correlated with annual CH₄ flux, presumably because high O:C in peat reflected the availability of easily degradable substrate for methanogenesis. The differences in C:N ratio indicated notable decomposition processes for Sphagnum-dominated peatlands but not in Carex-dominated peatlands. Degree of unsaturation showed potential for an integrative proxy for drainage-induced lowering water table and post-drainage changes in peat substrate quality.

中文翻译：

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林业排水对芬兰北方泥炭地表层泥炭化学计量和物理性质的影响

摘要

排水泥炭地的管理可能会对缓解气候变化带来风险或解决方案，因此需要评估林业排水泥炭地的现状、退化过程的程度和碳（C）损失指标。使用芬兰各地不同肥力等级泥炭地的大型数据集（778 个剖面、891 个泥炭样本，于 1977 年至 2017 年间收集），我们研究了不排水泥炭地和林业排水泥炭地的表面泥炭剖面在 C:N、von Post 和干堆积密度。从 16 个不排水泥炭剖面和 30 个排水泥炭剖面的子样本中进一步分析了元素比率（C:N:H 化学计量）作为退化场地指标的效用。这个排水地点的子样本测量了二氧化碳 (CO ₂ ) 和甲烷 (CH ₄ ) 通量，使我们能够将泥炭元素比率与年度 C 气体流出量联系起来。元素比 H:C、O:C 和 C:N 以及不饱和度（结合 C、N、H 变化）被发现广泛有效：它们捕获了泥炭植物来源的差异及其潜在的分解途径（C通过溶解的有机C和C气体损失和/或主要作为CO ₂的气体损失的组合而损失。在化学计量指标中，泥炭H:C比似乎是排水后退化的最佳指标，它不仅表明长期退化，而且解释了年CO ₂排放量变化的48%。 O:C 比率与年 CH ₄通量呈正相关，可能是因为泥炭中的高 O:C 反映了易于降解的产甲烷底物的可用性。 C:N 比率的差异表明以泥炭藓为主的泥炭地有显着的分解过程，但在以苔草为主的泥炭地中则不然。不饱和度显示出作为排水引起的地下水位降低和排水后泥炭基质质量变化的综合代理的潜力。