Tropical wetland methane emissions - processes and predictions: TropMethane

全球湿地甲烷排放的三分之二来自热带地区，但这一估计是不确定的，我们预测热带湿地甲烷排放变化的能力仍处于初级阶段。此外，我们不知道甲烷排放将如何对气候变化作出反应。在本项目中，我们将通过将现有的巴拿马长期泥炭地研究站点的新机制信息与刚果共和国、印度尼西亚和秘鲁泥炭地正在进行或已发表的研究数据相结合，解决这一知识缺口。总之，这些信息将使我们能够改进热带湿地甲烷通量的模型，从而改进对未来全球气候变化的估计。甲烷排放受到土壤微生物生产甲烷所需的氧气和有机基质输入量的强烈控制。随着氧气含量的增加，甲烷排放量下降，因为细菌将甲烷转化为二氧化碳，而且氧气对产生甲烷的微生物是有毒的。这减少了气候变暖，因为甲烷是一种比二氧化碳更强的温室气体。这项研究将量化泥炭中的氧气在多大程度上控制了热带湿地中甲烷的微生物生产和消耗。我们将通过实地测量和实验量化甲烷氧化和甲烷净通量的环境和微生物控制。例如，我们将确定微生物将甲烷氧化为二氧化碳的程度是由根部释放的氧气和大气中氧气进入泥炭土的运输刺激的。大气中的氧气通过地下水位下降或含氧雨水流入泥炭而输送到泥炭中。因此，我们将量化与现场这些过程有关的氧气输入。此外，树木可以通过从根部释放有机碳化合物到淹水的泥炭中来刺激甲烷的产生，因此我们也将测量从根部和植物凋落物中释放的不稳定化合物。为了建立氧气输入和甲烷通量之间的关系，我们将操纵地下水位并模拟根部氧气输入，以量化氧气输入如何影响甲烷通量。我们还将进行稳定同位素标记，以确定受控实验室条件下和实地甲烷氧化率。我们将把这些信息纳入现有的泥炭地模型，然后将其与JULES（一个大型生态系统模型，构成英国气象局气候模型的一个组成部分）联系起来。这将使我们能够预测热带湿地的甲烷排放，以及它们将如何应对气候变化。该项目是在全球气候模型中表示热带湿地甲烷排放的重要一步。

Two-thirds of global methane emissions from wetlands originate in the tropics, but this estimate is uncertain and our ability to predict variation in methane emissions from tropical wetland remains rudimentary. Furthermore, we do not know how methane emissions will respond to climate change. In this project we will address this knowledge gap by combining new mechanistic information from our existing long term peatland research site in Panama with data from ongoing or published research from peatlands in the Republic of Congo, Indonesia, and Peru. Together, this information will allow us to improve models of methane fluxes from tropical wetlands, and therefore refine estimates of future global climate change.Methane emissions are strongly controlled by the amount of oxygen and inputs of organic substrates needed for methane production by soil microbes. As oxygen levels increase, methane emissions decline as bacteria convert methane to carbon dioxide and because oxygen is toxic to methane producing microorganisms. This reduces climate warming because methane is a more potent greenhouse gas than carbon dioxide. This research will quantify the extent to which oxygen in the peat controls microbial production and consumption of methane in tropical wetlands. We will quantify the environmental and microbial controls of methane oxidation and net methane fluxes through field measurements and experiments. For example, we will determine the extent to which microbial oxidation of methane to carbon dioxide is stimulated by oxygen release from the roots and by transport of atmospheric oxygen into the peat soil. The transport of atmospheric oxygen into the peat could occur through water table draw-down or by oxygenated rainwater flowing into the peat. We will therefore quantify the oxygen inputs related to these processes in the field. Furthermore, trees can stimulate methane production by releasing organic carbon compounds from their roots into waterlogged peat, so we will also measure labile compounds released from roots and plant litter. To establish relationships between oxygen inputs and methane fluxes we will manipulate the water table and mimic root oxygen inputs to quantify how oxygen inputs affect methane fluxes. We will also conduct stable isotope labelling to determine rates of methane oxidation under controlled laboratory conditions and in the field. We will include this information into an existing peatland model, which will then be linked to JULES - a large-scale ecosystem model that forms a component of UK Met Office climate model. This will enable us to predict methane emissions from tropical wetlands and how these will respond to climate change. The project is an important step toward the representation of methane emissions from tropical wetlands in global climate models.