Testing the role of nutrient input thresholds in governing microbial-mediated carbon sequestration for temperate peatlands

我们的研究将为营养输入（主要是磷和氮）控制温带、雨养型泥炭地储存碳的效率的方式提供新的线索。我们最近对几个泥炭地进行了综合，这些泥炭地具有磷、氮和碳的年代和平行的核心剖面，这为长期泥炭地碳循环的新概念模型提供了基础（Schillereff等人，2021年）。全营养（雨养）泥炭地主要通过大气沉积获得养分，因此养分输入保持初级生产力和微生物分解有机物之间的紧密平衡。因此，我们假设营养输入阈值决定了几十年、几个世纪和几千年来泥炭地的碳封存效率和碳封存量。我们的研究突出了两个研究差距，阻止我们的概念模型进行测试：（i）微生物群落的活动和多样性的测量在古环境泥炭研究中明显缺乏，（ii）令人惊讶的是，很少有泥炭地对泥炭地碳循环的所有节点进行平行测量：气候，植被，营养物质，微生物和碳。我们的提案将实施一项创新的研究设计来测试我们的概念模型。在四个精心挑选的温带，在英国和瑞典，我们已经建立了研究组合的富营养泥炭地工作，我们将整合一些第一个DNA表征下核心微生物动力学与高分辨率重建的泥炭地碳循环的每个其他节点跨越过去2000年。这将使我们的假设，即养分输入阈值管理长期泥炭地固碳进行实证检验的第一次。为了实现这些目标，我们将：（一）从四个地点收集新的泥炭芯，并在常规深度对其微生物群落进行DNA表征;（二）在伦敦国王学院、利物浦大学、斯德哥尔摩大学和NERC环境组学设施完成每个其他节点的高分辨率测量;（iii）应用统计模型，量化泥炭地碳循环的每个驱动因素的作用和相互作用。选址（Holcroft和May Moss，英格兰; Store和Draftinge Mosse，瑞典）由我们广泛的基线数据指导，并从战略上捕获营养沉积，海拔和土地利用的梯度。通过以创新的方式将微生物活性的尖端宏基因组特征与其他驱动因素的常规测量相结合，我们将产生泥炭地碳循环的更完整的画面。在全球范围内，泥炭地是一个重要的碳库，包含三分之一的土壤碳库。泥炭地能有效地固碳，因为它们的积水和营养贫乏的条件减缓了有机物质的分解，而这与地表植被的生产力有关。这也意味着养分输入的微小变化可以引发碳储存的重大变化。近几十年来，人类活动加剧了P、N的沉积，改变了其他陆地生态系统的养分限制状况和碳循环。对未来泥炭地碳汇的影响尚不清楚。除了为我们的概念模型建立一个测试平台外，这些发现还应该促进泥炭地生态学，土壤微生物学和全球碳循环研究社区之间的更深层次的整合。我们希望我们的研究结果能够支持未来雄心勃勃的研究，旨在更好地了解温带泥炭地对21世纪气候和地球化学变化的适应能力。这将涉及参数化泥炭地发展的新数值模型，包括气候，植被，营养物质，微生物和碳的节点。随后整合到地球系统模型中，应该会产生21世纪泥炭地碳的更具代表性的轨迹。Schillereff et al. 2021，Comms.地球与环境2：1-10

Our research will shed new light on the ways nutrient input (primarily phosphorus and nitrogen) controls how efficiently temperate, ombrotrophic peatlands store carbon. Our recent synthesis of the few peatlands with well-dated and parallel core profiles of phosphorus, nitrogen and carbon underpinned a new conceptual model of long-term peatland carbon cycling (Schillereff et al. 2021). Ombrotrophic (rain-fed) peatlands derive nutrients primarily via atmospheric deposition, so nutrient input maintains the tight balance between primary productivity and the decomposition of organic matter by microbes. We therefore hypothesised that nutrient input thresholds govern how efficiently and how much carbon becomes sequestered in peatlands over decades, centuries and millennia. Our study highlighted two research gaps preventing our conceptual model being tested: i) measurements of the activity and diversity of microbial communities are strikingly absent from palaeoenvironmental peat research and (ii) surprisingly few peatlands have parallel measurements for all nodes of the peatland carbon cycle: climate, vegetation, nutrients, microbes and carbon. Our proposal will implement an innovative research design to test our conceptual model. Working at four carefully selected temperate, ombrotrophic peatlands in the UK and Sweden where we have established research portfolios, we will integrate some of the first DNA characterisation of down-core microbial dynamics with high-resolution reconstructions of each other node of the peatland carbon cycle spanning the last 2000 years. This will enable our hypothesis that nutrient input thresholds govern long-term peatland carbon sequestration to be empirically tested for the first time. To deliver these objectives, we will: (i) collect new peat cores from four sites and perform DNA characterisation of their microbial communities at regular depths; (ii) complete high-resolution measurements of each other node at King's College London, University of Liverpool, Stockholm University and the NERC Environmental Omics Facility; (iii) apply statistical modelling to quantify the role of and interplay between each driver of peatland carbon cycling. Site selection (Holcroft and May Moss, England; Store and Draftinge Mosse, Sweden) is guided by our extensive baseline data and strategically captures gradients of nutrient deposition, altitude and land-use. By combining in an innovate way cutting-edge metagenomic characterisation of microbial activity with conventional measurements of other drivers, we will produce a more complete picture of peatland carbon cycling. Globally, peatlands are a significant carbon store, containing one-third of the soil carbon pool. Peatlands sequester carbon efficiently because their waterlogged, nutrient impoverished conditions slow the decomposition of organic matter relative to the productivity of surface vegetation. This also means small changes in nutrient input can trigger significant shifts in carbon storage. Human activities have amplified P and N deposition in recent decades, which has changed the nutrient limitation status and carbon cycling in other terrestrial ecosystems. The implications for the future peatland carbon sink remain unclear. As well as establishing a testbed for our conceptual model, the findings should stimulate deeper integration between the peatland ecology, soil microbiology and global carbon cycling research communities. We intend our findings to underpin ambitious future research aimed at better understanding the resilience of temperate peatlands to both 21st-century climate and biogeochemical change. This will involve parameterising new numerical models of peatland development that encapsulate nodes for climate, vegetation, nutrients, microbes and carbon. Subsequent integration into Earth System models should produce more representative trajectories for peatland carbon through the 21st-century. Schillereff et al. 2021, Comms. Earth & Env. 2:1-10