Transport of oxygen in soil pore-water systems: implications for modeling emissions of carbon dioxide and methane from peatlands
Transport of oxygen in soil pore-water systems: implications for modeling emissions of carbon dioxide and methane from peatlands
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DOI：
10.1007/s10533-014-0012-0
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发表时间：
2014-12-01
期刊：
影响因子：
4
通讯作者：
Turetsky, Merritt R.
中科院分区：
文献类型：
--
作者：
Fan, Zhaosheng;Neff, Jason C.;Turetsky, Merritt R.
泥炭地储存了大量的土壤碳，是温室气体的重要来源，包括二氧化碳 (CO2) 和甲烷 (CH4) 排放。泥炭地排放生物地球化学模型模拟的传统方法是将土壤域简单地分为地下水位（WT）上方的好氧区和下方的厌氧区，然后根据这两个离散区域的假设属性计算CO2和CH4排放量。然而，传统的基于 WT 的方法存在重大潜在缺点，因为有氧或厌氧环境最终由氧气 (O-2) 浓度而不是直接由水含量决定。 WT 之上和之下的 O2 含量变化可能很大，因此可能在 CO2 和 CH4 之间的碳通量分配中发挥重要作用。在本文中，我们提出了一种基于氧气的方法，该方法模拟土壤有氧和厌氧环境中 O-2 运动和消耗的垂直和径向分量。然后，我们使用基于氧气的方法和传统的基于 WT 的方法来模拟阿拉斯加沼泽泥炭地的二氧化碳和甲烷排放。模型校准和验证的结果表明，我们的物理现实方法（即基于氧气的方法）对 CO2 和 CH4 的模拟通量造成的偏差较小。模型模拟的结果还表明，由于非饱和土壤中存在厌氧区，传统的基于小波变换的方法可能大大低估了沼泽地的 CH4 排放量并高估了 CO2 排放量。我们的基于氧的方法可以很容易地融入现有的生态系统或地球系统模型中，但需要在生物地球化学模型中实施更广泛的现场观测进行额外验证，以改善区域或全球范围内土壤碳通量的模拟。
Peatlands store vast amounts of soil carbon and are significant sources of greenhouse gases, including carbon dioxide (CO2) andmethane (CH4) emissions. The traditional approach in biogeochemical model simulations of peatland emissions is to simply divide the soil domain into an aerobic zone above and an anaerobic zone below the water table (WT) and then calculate CO2 and CH4 emissions based on the assumed properties of these two discrete zones. However, there are major potential drawbacks associated with the traditional WT-based approach, because aerobic or anaerobic environments are ultimately determined by oxygen (O-2) concentration rather than water content directly. Variations in O2 content above and below the WT can be large and thus may play an important role in partitioning of carbon fluxes between CO2 and CH4. In this paper, we propose an oxygen-based approach, which simulates the vertical and radial components of O-2 movement and consumption through the soil aerobic and anaerobic environments. We then use both our oxygen-based and the traditional WT-based approaches to simulate CO2 and CH4 emissions from an Alaskan fen peatland. The results of model calibration and validation suggest that our physically realistic approach (i.e., oxygen-based approach) cause less biases on the simulated flux of CO2 and CH4. The results of model simulations also suggest that the traditional WT-based approach might substantially under-estimate CH4 emissions and over-estimate CO2 emissions from the fen due to the presence of anaerobic zones in unsaturated soil. Our oxygen-based approach can be easily incorporated into existing ecosystem or earth system models but will require additional validation with more extensive field observations to be implemented within biogeochemical models to improve simulations of soil C fluxes at regional or global scale.