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，我们的重点是回答两个关键问题：（1） 是什么驱动了阿拉斯加富 Bonanza Creek 沼泽地二氧化碳 （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 m2 m-2）是由 CO2 施肥效应推动的，这共同导致了总初级生产力 （GPP） 的增加。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%）。