Constraining models for methane oxidation based on long-term continuous chamber measurements in a temperate forest soil
Constraining models for methane oxidation based on long-term continuous chamber measurements in a temperate forest soil
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DOI：
10.1016/j.agrformet.2021.108654
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发表时间：
2021-11
影响因子：
6.2
通讯作者：
M. Ueyama;Azusa Fujimoto;A. Ito;Yoshiyuki Takahashi;R. Ide
中科院分区：
文献类型：
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作者：
M. Ueyama;Azusa Fujimoto;A. Ito;Yoshiyuki Takahashi;R. Ide
由于甲烷氧化菌的氧化，旱地土壤被认为是CH4的汇，CH4是第二大人为温室气体。为了更好地了解高地森林中的CH4通量，我们使用自动封闭小室系统在日本火山土中的落叶松人工林上连续测量了七年多的CH4通量。我们假设长期数据足以校准CH4通量的模块，并旨在预测未来CH4吸收的途径及其在森林中的不确定性。根据观测，覆盖层的变薄只对两个房间测量的CH4通量产生了轻微的影响。利用贝叶斯方法的数据，我们校准了森林土壤中CH4通量的四个模块，这些模块嵌入了基于过程的生态系统模型访问中。在校正了以下参数后，这些模块很好地再现了观测到的甲烷通量的季节性、年度预算和年际变化：扩散系数或基本甲烷氧化速率常数和温度敏感性。在RCP8.5方案下，预计未来CH4通量将增加，但在RCP2.6方案下，CH4通量将减少。对比轨迹是由RCP 8.5和2.6情景下CH4浓度上升和下降引起的。此外，由于各模块对甲烷浓度变化的反应不一致，每个模块未来通量变化的幅度也不同。观测到的CH4通量随着大气CH4浓度(4.95mgCH4m−2d−1ppm−1)的增加而增加，其幅度大于模块中的值。考虑到模块中的不确定性和观测中的潜在混杂效应，我们得出结论，需要进一步了解CH4吸收对CH4浓度上升的反应。
Upland soils are thought to be a sink of CH4, the second most important anthropogenic greenhouse gas, owing to oxidation by methanotrophs. To better understand CH4fluxes in upland forests, we quasi-continuously measured CH4fluxes using an automated closed chamber system over seven years on a larch plantation in a volcanic soil in Japan. We hypothesized that the long-term data sufficiently can calibrate modules for CH4fluxes, and aimed to predict future pathways of CH4uptake and their uncertainties in the forest. Based on the observations, a thinning of the overstory only marginally influenced the CH4fluxes measured by the chambers. Using the data with a Bayesian method, we calibrated four modules for CH4fluxes in forest soils, which were embedded in the process-based ecosystem model VISIT. The modules well reproduced the observed seasonality, annual budgets, and interannual variability in the CH4fluxes after calibrating the following parameters: the diffusion coefficient or base CH4oxidation rate constant and temperature sensitivity. The CH4fluxes were predicted to increase in the future under the RCP8.5 scenario but to decrease under the RCP 2.6 scenario. The contrasting trajectory was caused by rising and decreasing CH4concentrations under the RCP 8.5 and 2.6 scenarios, respectively. Furthermore, the magnitudes of the future changes in the fluxes differed in each module because the responses to the changes in the CH4concentrations were inconsistent among the modules. The observed CH4fluxes increased with increasing atmospheric CH4concentration (4.95 mg CH4m−2d−1ppm−1), which was greater in magnitude than those in the modules. Considering the uncertainties in the modules and potential confounding effects in the observations, we conclude that further understanding the responses of CH4uptake to rising CH4concentrations is required.