Reconstructing past changes in wetland hydrology and carbon cycling

陆地环境中的微生物过程对于控制温室气体排放至关重要。现代土壤碳库超过陆地植被和大气的总和，土壤微生物每年循环1/3的光合碳，并占最大的天然甲烷通量。在此过程中，它们控制着我们星球的化学和气候状态。然而，这些过程仍然知之甚少，由一系列环境因素介导。可以从记录地球化学系统对过去环境扰动的反应的地质档案中获得见解。我们以前对泥炭和褐煤的研究为气候驱动的碳循环破坏提供了诱人的见解，但潜在的机制仍然没有得到解决。该项目将根据来自植物和细菌的泥炭有机物的同位素组成开发新的方法和记录，以解决这一问题。项目目标和方法：泥炭和褐煤长期以来一直被用来探索过去的气候变化，特别是温度和降水的变化。更难确定的是地球化学过程的变化。当天气变暖时，有机物（OM）的保存是由于更高的生产力而增强，还是由于微生物活动的增强而降解？如果降解，是否表现为二氧化碳通量的增加？或者甲烷？或者两者都不是，因为微生物也适应消耗这些温室气体之前，他们可以逃离湿地？通过确定泥炭中单个化合物的碳同位素组成，我们获得了一些见解，一些来自植物，另一些来自微生物，使我们能够探测环境破坏期间碳流的再平衡。然而，我们目前的调查是有限的，主要集中在温带而不是热带湿地。到目前为止，我们还无法解决微生物生态学中更细微的变化。在这个项目中，我们将探索和比较威尔士，英国，巴拿马和哥伦比亚泥炭地的环境和地球化学破坏（与博士生和监督团队合作开发的特定地点和时间间隔）。然后，我们将完善和应用最新的分析创新-细菌氢同位素组成的测定-以确定泥炭地水文，细菌代谢和碳循环的过去变化之间的关系。

Project Background Microbial processes in terrestrial settings are critical to governing greenhouse gas emissions. The modern carbon soil reservoir exceeds that of terrestrial vegetation and the atmosphere combined, and soil microorganisms annually cycle 1/3 of the carbon photosynthesised and account for the largest natural methane flux. In doing so, they govern the chemical and climatic state of our planet. And yet these processes remain poorly understood, mediated by a range of environmental factors. Insight can be derived from geological archives that document the responses of biogeochemical systems to past environmental perturbations. Our previous studies on peat and lignites provide tantalising insights into climate-driven disruption of the carbon cycle, but the underlying mechanisms remain unresolved. This project will address that by developing new approaches and records based on the isotopic composition of peat organic matter derived from plants and bacteria. Project Aims and Methods: Peat and lignite deposits have long been used to explore past changes in climate, especially changes in temperature and precipitation. What is much harder to ascertain are changes in biogeochemical processes. When it becomes warmer is organic matter (OM) preservation enhanced due to higher productivity or is that OM degraded due to enhanced microbial activity? If degraded, is that manifested as an increased flux of carbon dioxide? Or methane? Or neither because microorganisms also adapt to consume these greenhouse gases before they can escape from the wetland? We have obtained some insight by determining the carbon isotopic composition of individual compounds in the peat, some derived from plants and others derived from microorganisms, allowing us to probe the rebalancing of carbon flow during environmental disruption. However, our current investigations are limited, having focused primarily on temperate rather than tropical wetlands. We have also been unable to resolve, until now, more nuanced changes in microbial ecology. In this project, we will explore and compare environmental and biogeochemical disruptions in Welsh, English, Panamanian and Colombian peatland (the specific sites and time intervals developed in collaboration with the PhD student and the supervisory team). We will then refine and apply recent analytical innovations - the determination of bacterial hydrogen isotopic compositions - to ascertain the relationships between past changes in peatland hydrology, bacterial metabolism and carbon cycling.