Peatlands play an important role in the global carbon cycle as they contain a large soil carbon stock. However, current climate change could potentially shift peatlands from being carbon sinks to carbon sources. Remote sensing methods provide an opportunity to monitor carbon dioxide (CO₂) exchange in peatland ecosystems at large scales under these changing conditions. In this study, we developed empirical models of the CO₂ balance (net ecosystem exchange, NEE), gross primary production (GPP), and ecosystem respiration (ER) that could be used for upscaling CO₂ fluxes with remotely sensed data. Two to three years of eddy covariance (EC) data from five peatlands in Sweden and Finland were compared to modelled NEE, GPP and ER based on vegetation indices from 10 m resolution Sentinel-2 MSI and land surface temperature from 1 km resolution MODIS data. To ensure a precise match between the EC data and the Sentinel-2 observations, a footprint model was applied to derive footprint-weighted daily means of the vegetation indices. Average model parameters for all sites were acquired with a leave-one-out-cross-validation procedure. Both the GPP and the ER models gave high agreement with the EC-derived fluxes (R² = 0.70 and 0.56, NRMSE = 14% and 15%, respectively). The performance of the NEE model was weaker (average R² = 0.36 and NRMSE = 13%). Our findings demonstrate that using optical and thermal satellite sensor data is a feasible method for upscaling the GPP and ER of northern boreal peatlands, although further studies are needed to investigate the sources of the unexplained spatial and temporal variation of the CO₂ fluxes.

中文翻译：

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利用卫星遥感数据扩大北部泥炭地二氧化碳通量

泥炭地在全球碳循环中起着重要作用，因为它们含有大量的土壤碳储量。但是，当前的气候变化可能会将泥炭地从碳汇转变为碳源。在这些变化的条件下，遥感方法提供了一个机会来大规模监测泥炭地生态系统中的二氧化碳（CO ₂）交换。在这项研究中，我们开发了可用于提升CO ₂比例的CO ₂平衡（净生态系统交换，NEE），初级生产总值（GPP）和生态系统呼吸（ER）的经验模型。带有遥感数据的流量。根据来自10 m分辨率Sentinel-2 MSI的植被指数和来自1 km分辨率MODIS数据的地表温度，将瑞典和芬兰五个泥炭地两到三年的涡度协方差（EC）数据与模拟的NEE，GPP和ER进行了比较。为了确保EC数据与Sentinel-2观测值之间的精确匹配，应用了足迹模型来得出植被指数的足迹加权日均值。使用留一法交叉验证程序获取所有站点的平均模型参数。GPP模型和ER模型均与EC衍生的通量高度吻合（R ² = 0.70和0.56，NRMSE = 14％和15％）。NEE模型的性能较弱（平均R ²= 0.36，NRMSE = 13％）。我们的发现表明，使用光学和热卫星传感器数据是提高北方北方泥炭地GPP和ER规模的可行方法，尽管还需要进一步的研究来调查无法解释的CO ₂通量的时空变化来源。