A new approach to simulate peat accumulation, degradation and stability in a global land surface scheme (JULES vn5.8_accumulate_soil) for northern and temperate peatlands
A new approach to simulate peat accumulation, degradation and stability in a global land surface scheme (JULES vn5.8_accumulate_soil) for northern and temperate peatlands
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DOI：
10.5194/gmd-15-1633-2022
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发表时间：
2022-02
影响因子：
5.1
通讯作者：
S. Chadburn
中科院分区：
文献类型：
--
作者：
S. Chadburn
抽象的。泥炭地在地球系统模型(ESM)中常常被忽视。在包括它们的地方，它们通常通过一个单独的、规定的网格单元分数来表示，该网格单元分数被赋予泥炭(高度有机)土壤的物理特性。然而，在现实中，土壤的光谱在纯矿物土壤(不含有机物质)和纯有机土壤之间存在差异，通常在矿物土壤下面覆盖一层厚度可变的有机层。它们也是动态的，有机层的厚度及其特性随着时间的推移而变化。无论是土壤类型的光谱还是它们的动态性质，都不能被当前的ESM捕捉到。在这里，我们提出了一个新版本的ESM陆地表面方案(联合英国陆地环境模拟器，JLES)，其中土壤有机质积累--从而泥炭地的形成、退化和稳定性--被整合到垂直分辨率的土壤碳方案中。我们还介绍了在Jules中跟踪土壤碳年龄作为深度的函数的能力，并将其与测量的泥炭年龄-深度剖面进行比较。新方案在北部和温带地区进行了测试和评估。该方案模拟了土壤有机质与其热工水力特性之间的动态反馈关系。我们表明，排干泥炭地可以导致显著的碳损失、土壤紧实度和泥炭性质的变化。然而，负反馈可能会导致泥炭地在排水后重新湿润自己。这些生态水文反馈也可能导致泥炭地在泥炭形成不会在模型中开始形成的气候中保持自身，即显示出一定程度的弹性。新的模型产生了与原始的矿物土壤模型和泥炭地土壤有机碳的真实剖面相似的结果。我们根据全球泥炭岩芯数据集中的216个北部和温带地点的典型泥炭剖面对该模型进行了评估。在性能最好的Jules-Peat模拟中，土壤碳剖面的均方根误差(RMSE)比标准Jules配置降低了35%-80%。不同气候带土壤碳的均方根误差为7.7~16.7kgCm−3，远小于土壤碳含量(约30~60kgCm−3)。与原始的朱尔斯配置相比，朱尔斯-泥炭中矿质土壤的RMSE也降低了(减少了∼30%-50%)。因此，Jules-Peat可以作为一个完整的方案来模拟有机土壤和矿物土壤。它不需要任何额外的输入数据，并且在模型中引入了最少的额外变量。这为改进有机和泥炭地土壤的模拟以及相关的碳循环反馈提供了一种新的途径。
Abstract. Peatlands have often been neglected in Earth system models (ESMs). Where they are included, they are usually represented via a separate, prescribed grid cell fraction that is given the physical characteristics of a peat (highly organic) soil. However, in reality soils vary on a spectrum between purely mineral soil (no organic material) and purely organic soil, typically with an organic layer of variable thickness overlying mineral soil below. They are also dynamic, with organic layer thickness and its properties changing over time. Neither the spectrum of soil types nor their dynamic nature can be captured by current ESMs. Here we present a new version of an ESM land surface scheme (Joint UK Land Environment Simulator, JULES) where soil organic matter accumulation – and thus peatland formation, degradation and stability – is integrated in the vertically resolved soil carbon scheme. We also introduce the capacity to track soil carbon age as a function of depth in JULES and compare this to measured peat age–depth profiles. The new scheme is tested and evaluated at northern and temperate sites. This scheme simulates dynamic feedbacks between the soil organic material and its thermal and hydraulic characteristics. We show that draining the peatlands can lead to significant carbon loss, soil compaction and changes in peat properties. However, negative feedbacks can lead to the potential for peatlands to rewet themselves following drainage. These ecohydrological feedbacks can also lead to peatlands maintaining themselves in climates where peat formation would not otherwise initiate in the model, i.e. displaying some degree of resilience. The new model produces similar results to the original model for mineral soils and realistic profiles of soil organic carbon for peatlands. We evaluate the model against typical peat profiles based on 216 northern and temperate sites from a global dataset of peat cores. The root-mean-squared error (RMSE) in the soil carbon profile is reduced by 35 %–80 % in the best-performing JULES-Peat simulations compared with the standard JULES configuration. The RMSE in these JULES-Peat simulations is 7.7–16.7 kg C m−3 depending on climate zone, which is considerably smaller than the soil carbon itself (around 30–60 kg C m−3). The RMSE at mineral soil sites is also reduced in JULES-Peat compared with the original JULES configuration (reduced by ∼ 30 %–50 %). Thus, JULES-Peat can be used as a complete scheme that simulates both organic and mineral soils. It does not require any additional input data and introduces minimal additional variables to the model. This provides a new approach for improving the simulation of organic and peatland soils and associated carbon-cycle feedbacks in ESMs.