Modeled Microbial Dynamics Explain the Apparent Temperature Sensitivity of Wetland Methane Emissions
Modeled Microbial Dynamics Explain the Apparent Temperature Sensitivity of Wetland Methane Emissions
复制标题
DOI：
10.1029/2020gb006678
复制
发表时间：
2020-11-01
影响因子：
5.2
通讯作者：
Westermann, Sebastian
中科院分区：
文献类型：
--
作者：
Chadburn, Sarah E.;Aalto, Tuula;Westermann, Sebastian
天然湿地的甲烷排放量随温度升高而增加，因此在未来气候变化下可能导致正反馈。然而，它们的温度响应包括混杂因素，并且在不同的时间尺度上似乎有所不同。观测到的甲烷排放量在季节基础上很大程度上依赖于温度，但如果将各站点之间的年平均排放量进行比较，则只有很小的温度影响。我们假设微生物动力学是季节周期的主要驱动因素，并且它们可以解释这种明显的差异。我们将一个相对简单的产甲烷生长和休眠模型引入到一个用于地球系统模型的湿地甲烷方案中。我们发现，这一增加量足以再现完全饱和湿地中观测到的甲烷排放的季节动态，同时再现年平均排放量。我们发现，在最近的地球系统模型中使用的更复杂的方案并没有增加预测能力。所使用的地点跨越了一系列的气候条件，大多数在高纬度地区。所测试的非微生物方案不能再现表观温度敏感性的季节和空间差异。因此，我们得出结论，微生物动力学是驱动湿地甲烷排放季节性循环的有力候选。我们使用该方案量化了较长期的温度敏感性，并表明全球每变暖一度，其排放量将增加约12%。这还不包括任何水文变化，这也可能影响未来的甲烷排放。
Methane emissions from natural wetlands tend to increase with temperature and therefore may lead to a positive feedback under future climate change. However, their temperature response includes confounding factors and appears to differ on different time scales. Observed methane emissions depend strongly on temperature on a seasonal basis, but if the annual mean emissions are compared between sites, there is only a small temperature effect. We hypothesize that microbial dynamics are a major driver of the seasonal cycle and that they can explain this apparent discrepancy. We introduce a relatively simple model of methanogenic growth and dormancy into a wetland methane scheme that is used in an Earth system model. We show that this addition is sufficient to reproduce the observed seasonal dynamics of methane emissions in fully saturated wetland sites, at the same time as reproducing the annual mean emissions. We find that a more complex scheme used in recent Earth system models does not add predictive power. The sites used span a range of climatic conditions, with the majority in high latitudes. The difference in apparent temperature sensitivity seasonally versus spatially cannot be recreated by the non-microbial schemes tested. We therefore conclude that microbial dynamics are a strong candidate to be driving the seasonal cycle of wetland methane emissions. We quantify longer-term temperature sensitivity using this scheme and show that it gives approximately a 12% increase in emissions per degree of warming globally. This is in addition to any hydrological changes, which could also impact future methane emissions.