Tropical wetland methane emissions - processes and predictions: TropMethane

摘要全球湿地甲烷排放量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量的能力仍然是初步的。此外，我们不知道甲烷排放将如何应对气候变化。在这个项目中，我们将解决这个知识差距相结合，从我们现有的长期在巴拿马的湿地研究网站的数据正在进行或发表的研究从刚果共和国，印度尼西亚和秘鲁的湿地新的机械信息。该项目针对两个重要的甲烷通量控制过程：甲烷氧化和与根系分泌物有关的甲烷生产。该项目将测量这些过程以及相关的环境和微生物驱动因素。然后，我们将使用这些数据将这两个过程纳入大尺度模型中，以估计热带湿地的甲烷净排放量。由于地下水位下降，含氧降雨和根系的输入，湿地饱和土壤中的氧气水平可能会增加。随着氧气水平的增加，甲烷排放量下降，因为细菌将甲烷转化为二氧化碳，并且因为氧气对产甲烷微生物有毒。这项研究将量化土壤中的氧气在多大程度上控制热带湿地中微生物的甲烷生产和消耗。腐烂的有机物和根系释放的不稳定有机化合物的基质可用性影响甲烷的产生，将甲烷的产生与土壤中的有机物和根系分泌物联系起来。在这个项目中，我们将确定树木根系分泌物输入的数量和类型，以提高我们对树木如何影响湿地甲烷产生的理解。例如，我们将从根区收集水样，以确定存在的不同有机化合物，并在不同树种之间比较这些结果。为了全面了解影响甲烷通量的不同过程，我们将对甲烷氧化，生产和净排放的环境和微生物控制进行详细测量。在我们的实地工作中，我们将确定在何种程度上增加了微生物氧化甲烷的实验模拟根氧输入和地下水位下降。我们还将进行稳定同位素标记实验，以确定甲烷氧化率和直接在现场微生物的生产。我们将把这些信息纳入现有的湿地甲烷排放模型，并将其整合到JULES -一个大规模的生态系统模型，形成英国气象局气候模型的一个组成部分。这将使我们能够预测热带湿地的甲烷排放量以及这些排放量将如何应对气候变化。该项目是在全球气候模型中代表热带湿地甲烷排放的重要一步。

SummaryTwo-thirds of global methane emissions from wetlands originate in the tropics, but this estimate is uncertain and our ability to predict 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 wetland research site in Panama with data from ongoing or published research from wetlands in the Republic of Congo, Indonesia, and Peru. This project targets two processes that are important controls of methane fluxes: methane oxidation and methane production linked to root exudates. This project will measure these processes and associated environmental and microbial drivers in the field. We will then use this data to incorporate both of these processes in large scale models to estimate net methane emissions from tropical wetlands.Oxygen levels in the saturated soils of wetlands can increase due to the water table falling, inputs from oxygenated rainfall and from roots. As oxygen levels increase, methane emissions decline as bacteria convert methane to carbon dioxide, and because oxygen is toxic to methane-producing microorganisms. This research will quantify the extent to which oxygen in the soil controls microbial production and consumption of methane in tropical wetlands. The substrate availability from decaying organic matter and labile organic compounds released from roots affect methane production, linking methane production both to the organic matter in the soil and root exudates. In this project, we will determine the amounts and types root exudate inputs from trees to improve our understanding of how trees affect methane production in wetlands. For example, we will collect water samples from the root zone to determine the different organic compounds present, and compare these results between different tree species. To develop a full understanding of the different processes impacting methane fluxes we will carry out detailed measurement of environmental and microbial controls of methane oxidation, production and net emissions. In our field work, we will determine the extent to which microbial oxidation of methane is increased by experimental simulation of root oxygen inputs and water table draw down. We will also conduct stable isotope labelling experiments to determine rates of methane oxidation and production by microbes directly in the field. We will include this information into an existing wetland methane emissions model and integrate this into 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.