Boreal peatlands store vast amounts of soil organic carbon (C) owing to the imbalance between productivity and decay rates. In the recent decades, this carbon stock has been exposed to a warming climate. During the past decade alone, the Arctic has warmed by ∼ 0.75°C which is almost twice the rate of the global average. Although, a wide range of studies have assessed peatlands’ C cycling, our understanding of the factors governing source / sink dynamics of peatland C stock under a warming climate remains a critical uncertainty at site, regional, and global scales. Here our focus was on answering two key questions: (1) What drives the interannual variability of carbon dioxide (CO₂) fluxes at the Bonanza Creek rich fen in Alaska, and (2) What are the internal carbon allocation patterns during the study years? We addressed these knowledge-gaps using an intermediate complexity terrestrial ecosystem model calibrated by a Bayesian model-data fusion framework at a weekly timestep with publicly available eddy covariance, satellite-based earth observation, and in-situ datasets for 2014 to 2020. We found that the greening trend (a relative increase of leaf area index ∼0.12 m² m^-2 by 2020) in the fen ecosystem is forced by a CO₂ fertilisation effect which in combination resulted in increased gross primary production (GPP). Relative to 2014, GPP increased by ∼75 gC m^-2 year^-1 (by 2020; 95% confidence interval (CI): -41.35 gC m^-2 year^-1 to 213.55 gC m^-2 year^-1) while heterotrophic respiration stayed constant. Consistent with the observed greening, our analysis indicates that the ecosystem allocated more C to foliage (∼50%) over the structural (A carbon pool consisting of branches, stems and coarse roots; ∼30%) and fine root C pools (∼20%).

中文翻译：

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二氧化碳施肥驱动的富含北方的沼泽地的绿化


由于生产力和腐烂速度之间的不平衡，北方泥炭地储存了大量的土壤有机碳 （C）。近几十年来，这些碳储量一直暴露在气候变暖的环境中。仅在过去十年中，北极就变暖了约 0.75°C，几乎是全球平均水平的两倍。尽管有广泛的研究评估了泥炭地的 C 循环，但我们对气候变暖下泥炭地 C 种群源/汇动力学因素的理解仍然是现场、区域和全球尺度的关键不确定性。在这里，我们重点回答了两个关键问题：（1） 是什么驱动了阿拉斯加 Bonanza Creek 富沼地二氧化碳 （CO₂） 通量的年际变化，以及 （2） 研究期间的内部碳分配模式是什么？我们使用中等复杂度的陆地生态系统模型解决了这些知识差距，该模型由贝叶斯模型-数据融合框架在每周时间步校准，具有公开可用的涡流相关、基于卫星的地球观测和 2014 年至 2020 年的原位数据集。我们发现，沼泽生态系统的绿化趋势（到 2020 年叶面积指数相对增加 ∼0.12 m^{2 m-2}）是由 CO₂ 施肥效应推动的，这共同导致总初级生产力 （GPP） 增加。相对于 2014 年，GPP 在 ²⁰²⁰ 年增加了 ∼75 gC ^m-2 （到 2020 年;95% 置信区间 （CI）：-41.35 gC ^{m-2 year-1} 至 213.55 gC ^{m-2 year-1}），而异养呼吸保持不变。 与观察到的绿化一致，我们的分析表明，生态系统为叶子分配了更多的碳 （∼50%），而不是结构性（由树枝、茎和粗根组成的碳库;∼30%）和细根碳库 （∼20%）。