Environmental and ecological drivers of tropical peatland methane dynamics across spatial scales

热带泥炭地是全球重要的碳库，也是大气中甲烷(CH4)浓度上升的重要来源。CH4是一种强有力的温室气体，100年来推动气候变暖的力量是二氧化碳(CO2)的25倍，迄今对全球变暖的贡献率为23%。在COP26上，美国、欧盟和其他国家宣布了全球甲烷承诺，以遏制全球甲烷排放，试图将全球变暖控制在1.5摄氏度。然而，大气中的甲烷浓度正在上升，有证据表明热带湿地和泥炭地是重要的来源，特别是在南美洲。造成这一现象的潜在环境原因还没有得到很好的理解。热带泥炭地遍布热带，但到目前为止，大多数研究都集中在东南亚。然而，最近的研究表明，中非和南美洲都有广泛的泥炭矿藏，但这些生态系统的动态仍然相对较少。泥炭是由部分降解的植物材料形成的，包括树叶和根。在淹水、低氧条件下的逐渐分解推动了CH4的产生。生产和排放的速度受包括水文、养分可获得性、地形和植被在内的多种因素的控制。这些因素中的许多可以在空间上变化，并随着时间的推移而变化。这限制了我们将地面上的CH4排放测量扩大到更广泛区域的能力，因此我们无法充分评估区域泥炭地对全球CH4循环的贡献。在这个项目中，我们将解决这些不确定性，对热带泥炭地CH4排放的环境和生态驱动因素产生新的综合理解，并首次将它们完全纳入数学模型。这将使我们能够更准确地将甲烷排放的现场测量扩大到更广泛的区域，使我们能够评估热带泥炭地甲烷通量对大气中甲烷浓度上升的贡献。我们将在秘鲁Pastaza-Maranon前陆盆地的南美泥炭地进行新的长期CH4通量测量。我们将把我们的通量测量与生态系统生产力、泥炭特性和养分有效性随时间的变化以及不同植被类型和养分有效性的泥炭地的持续监测相结合。我们将使用一个统计工具，使我们能够确定哪些因素对预测CH4通量最重要。我们将利用这一结果来修改现有的模型(EcoSe)，以便更好地解释这些过程，从而更准确地向上放大更广泛区域的CH4通量。为了帮助开发和测试我们的统计工具和ECosse模型，我们将利用从中非泥炭地新收集的数据，该地区在CH4通量动力学方面也研究得很少，但在植被类型和营养制度方面似乎与南美洲有许多相似之处。然后，我们将应用我们新开发的统计工具和模型，将我们在南美泥炭地的CH4通量测量更准确地升级到更广泛的区域。我们还将能够使用我们最新开发的模型来测试该地区湿地甲烷排放量增加的各种解释，调查包括水系变化、植被输入和气候变暖在内的原因。从项目初期开始，一直持续到整个项目，我们将与英国、秘鲁和国际上的合作伙伴密切合作，以确定区域和国际利益攸关方。我们将共同开展我们的研究，并将我们的项目结果转化为非专业总结，为决策者提供信息，并提高人们对泥炭地过程对全球环境变化敏感性的认识。

Tropical peatlands are a globally important carbon store, and a significant source of rising atmospheric concentrations of methane (CH4). CH4 is a potent GHG, 25 times more powerful at driving climate warming than carbon dioxide (CO2) over 100 years, and is responsible for 23% of warming to date. At COP26, the US, EU and others announced the Global CH4 Pledge to curb global CH4 emissions in an attempt to keep global warming at 1.5C. However, atmospheric CH4 concentrations are rising with evidence pointing to tropical wetlands and peatlands as significant sources, particularly those in South America. The underlying environmental causes of this are not well understood. Tropical peatlands are found throughout the tropics but to date most research has focussed on Southeast Asia. However, recent research has demonstrated extensive peat deposits across both Central Africa and South America but the dynamics of these ecosystems remain relatively understudied. Peat is formed from partially degraded plant material, including leaf litter, and roots. Gradual decomposition under flooded, low oxygen conditions drives CH4 production. Rates of production and emission are controlled by a combination of factors including hydrology, nutrient availability, topography, and vegetation. Many of these factors can vary spatially and change over time. This limits our ability to scale up CH4 emissions measurements made on the ground to the wider region, and therefore prevents us from fully assessing the contribution of regional peatlands to global CH4 cycling. In this project, we will address these uncertainties, and generate a new integrated understanding of the environmental and ecological drivers of CH4 emissions from tropical peatlands, and incorporate them fully in mathematical models for the first time. This will allow us to more accurately upscale field based measurements of CH4 emissions to the wider region, allowing us to assess the contribution of tropical peatland CH4 fluxes to rising atmospheric concentration of CH4. We will undertake new long-term CH4 flux measurements across South American peatlands in the Pastaza-Maranon Foreland Basin in Peru. We will integrate our flux measurements with ongoing monitoring of ecosystem productivity and changes in peat properties and nutrient availabilities over time, and across peatlands that differ in vegetation type and nutrient availability. We will use a statistical tool that will allow us to identify which factors are most important for predicting CH4 fluxes. We will use the outcomes from this to modify an existing model (ECOSSE) to better account for these processes allowing more accurate upscaling of CH4 fluxes for the wider region. To help develop and test our statistical tool and ECOSSE model, we will make use of newly collected data from Central African peatlands, a region which is also poorly studied in terms of CH4 flux dynamics, but appears to have many similarities to South America in terms of vegetation types, and nutrient regimes. We will then apply our newly developed statistical tool and model to more accurately upscale our CH4 flux measurements across South American peatlands to the wider region. We will also be able to use our newly developed models to test various explanations for the observed increase in CH4 emissions across the region's wetlands, investigating causes including changes in water regimes, vegetation inputs, and climate warming. Beginning early in the project, and continuing throughout, we will work closely with partners in the UK, Peru and internationally, to identify regional and international stakeholders. Together, we will co-develop our research, and translate our project findings into lay summaries to inform policymakers, and raise awareness of the sensitivity of peatland processes to global environmental changes.