Linking Microbial Physiology with Carbon Transformations in Peatlands Under Land Use Change

大量的碳储存在土壤中，特别是在泥炭地。不断增加的粮食和能源需求导致了密集的土地利用做法，耗尽了土壤有机碳（SOC）储量。在苏格兰，大片泥炭地的农业和商业林业排水造成了泥炭地的退化和大量的碳损失。它们最近的恢复导致了有机碳封存的回归，并带来了相关的气候效益，但潜在的碳循环机制尚不清楚。这种机制的理解需要更好地预测和管理土壤过程，以保持甚至提高泥炭地的有机碳储量，同时节约土地利用。微生物在这方面是至关重要的，因为它们的生长和活动在很大程度上控制着近期植物碳输入的命运，以及同化微生物碳的稳定性。土壤中微生物分解速率和有机碳稳定之间的平衡在环境条件的改变下会发生变化。在泥炭地，水淹条件、厌氧和酸性限制了微生物的生长和分解，从而导致有机碳的保存。泥炭地的排水退化消除了导致有机碳保存的因素，从而通过微生物分解导致有机碳的损失。恢复性方法旨在扭转这些影响，从而限制有机碳的损失；然而，人们对确切的水文、化学和生物机制及其相互依赖性知之甚少。本项目旨在了解泥炭地退化和随后恢复对微生物生理过程的影响及其对土壤碳转化的影响。项目将严格检验泥炭地的微生物生长、活动和分解受酸度和厌氧作用限制的假设；泥炭地的退化会导致微生物的增加，从而导致泥炭有机质的分解。我们将进入苏格兰不同土地使用类型下的多个泥炭地站点来测试假设。目的是评估微生物的碳循环功能，如生长速度、碳利用效率、资源分解和吸收、维持和耐受性。这些群落特征将使用稳定同位素示踪和散弹枪宏基因组学相结合的方法进行量化，并使用FTIR等化学分子工具评估它们驱动SOC变化的指纹。利用稳定同位素示踪剂，我们将测量微生物将碳纳入生物量和通过呼吸损失，以量化不同土地利用类型的碳利用效率、生长速度和特定呼吸等群落水平性状。阿伯丁大学（UoA）和詹姆斯·赫顿研究所（JHI）的气体、固体、土壤溶液和化合物特定的13C同位素比质谱（IRMS）分析设施（包括腔衰荡谱法（CRDS））是独一无二的，培训将由监督团队提供。利用全基因组霰弹枪宏基因组学研究不同土地利用方式下泥炭地微生物群落的功能。这里的目标是提取在不同土地利用下土壤中占主导地位的微生物的生理特征。UoA的基因组生物学和医学中心（www.abdn.ac.uk/genomics）拥有Illumina NextSeq500和Oxford Nanopore GridION等DNA测序平台，这些平台将为该项目提供分子方法和生物信息学方面的培训。现有有机质的化学分析将用于利用FTIR在分子水平上表征泥炭地有机质。一旦我们能够在微生物特性和碳循环过程之间形成联系，我们将能够利用这些综合知识来确定恢复实践在改变旨在恢复和封存泥炭地碳的微生物生理学方面的功效。

Significant amount of carbon is stored in soils, particularly in peatlands. Increasing food and energy needs have led to intensive land use practices that deplete soil organic carbon (SOC) stores. In Scotland, drainage for agriculture and commercial forestry in its vast swathes of peatlands has caused their degradation with significant loss of carbon. Their recent restoration has led to the return of SOC sequestration, and associated climate benefits, but the underlying carbon cycling mechanisms have not been clearly understood. This mechanistic understanding is required to better predict and manage soil processes to maintain or even enhance SOC storage in peatlands while economising land-use.Microorganisms are critical in this regard because their growth and activity largely control the fate of recent plant carbon inputs, as well as the stability of assimilated microbial carbon. The balance between the rate of microbial decomposition and stabilisation of organic carbon in soil can shift under altered environmental conditions. In peatlands, water-logged conditions, anaerobiosis and acidity limit microbial growth and decomposition that consequently causes preservation of organic carbon. Peatland degradation through drainage removes the factors causing organic carbon preservation thus leading to SOC loss through microbial decomposition. Restorative approaches aim at reversing these effects thereby limiting the loss of SOC; however, the exact hydrological, chemical and biotic mechanisms and their inter-dependencies are poorly understood.This project aims at understanding the effects of peatland degradation and subsequent restoration on microbial physiological processes and their consequences on soil carbon transformations. Project will rigorously test the hypotheses that microbial growth, activity and decomposition is limited by acidity and anaerobiosis in peatlands; and that peatland degradation causes increased microbial growth and consequently decomposition of peat organic matter. We will have access to multiple peatland sites under various land use types across Scotland to test the hypotheses. The goal is to assess microbial carbon cycling functions like growth rate, carbon use efficiency, resource breakdown and uptake, maintenance and stress tolerance. These community traits will be quantified using a combination of stable isotope tracing and shot-gun metagenomics, and their fingerprints in driving changes in SOC will be assessed using chemical molecular tools like FTIR.Using stable isotope tracers, we will measure microbial incorporation of carbon into biomass and loss through respiration to quantify community-level traits like carbon use efficiency, growth rate and specific respiration across land use types. Analytical facilities for gas, solid, soil solution and compound-specific 13C isotope ratio mass spectrometry (IRMS) including cavity ring-down spectrometry (CRDS) at University of Aberdeen (UoA) and James Hutton Institute (JHI) are unique and training will be provided by the supervisory team. Whole genome shot-gun metagenomics will be used to investigate functions of peatland microbial communities under different land use. The goal here will be to extract physiological traits of microbes that are dominant in soils under different land use.The Centre for Genome Enabled Biology and Medicine (www.abdn.ac.uk/genomics) at UoA houses DNA sequencing platforms like Illumina NextSeq500 and Oxford Nanopore GridION which will be available to the project including training in molecular methods and bioinformatics. Chemical analysis of the extant organic matter will be used to characterise peatland organic matter at the molecular level using FTIR. Once we are able to form a link between microbial traits and carbon cycling processes, we will be able to use the combined knowledge to ascertain the efficacy of restorative practices in changing microbial physiology aimed at regaining and sequestering carbon in peatlands.