OPUS: MCS - What Remains? Quantifying the First Steps of Soil Organic Carbon Formation

作品：MCS - 还剩下什么？

• 批准号: 1950775
• 负责人: Carol Adair
• 金额: $ 18.91万
• 依托单位: University of Vermont & State Agricultural College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1950775&HistoricalAwards=false
• 关键词: OPUS; MCS; What; Remains; Quantifying

The processes by which carbon-rich plant detritus (dead leaves, roots, stems, and limbs) is incorporated into soil are not well understood. For nearly a century, most of the carbon in soils was thought to consist of plant-based compounds resistant to decomposition by microbial organisms (the recalcitrant soil carbon hypothesis). More recent research indicates that microbes can decompose virtually all plant-derived compounds, and that soil carbon consists largely of microorganisms and compounds they produce. If complete decomposition of plant detritus is found to be a widespread phenomenon, it would upend the paradigm of recalcitrant soil carbon, and necessitate changes in global models of carbon flux. Because microbes produce compounds distinct from those in plant detritus, the fraction of soil carbon that is microbially-derived can be inferred from the chemical fingerprint they leave in the soil. This project will use a state-of-the-art analytical chemistry method to characterize the extent of this microbial fingerprint on archived samples from a 10-year decomposition experiment (form the tropics to the tundra). The resulting data will be used to determine if plant detritus generates a significant pool of undecomposable carbon in the soil, or if essentially all plant detritus is transformed into microbial biomass. This refined understanding will augment the current conceptual framework for soil carbon formation, and will enable the process of soil carbon formation to be more accurately represented in models. This project will also develop a quantitative teaching unit on soil carbon formation and litter decomposition modeling, which will be open access and available to the broader educational community.The development of an accurate conceptual model is hindered by methods and data that fail to accurately quantify changes in litter chemistry during decomposition. This project will address this gap by quantifying how litter chemistry changes over time, across climates, and with position (above- vs. belowground), using solid-sate 13C-NMR to characterize archived samples from one of the most spatially extensive long-term decomposition experiments in the world (Long-term Intersite Decomposition Team, LIDET). Specifically, this project will address three questions with the goal of creating a new conceptual model of litter decomposition: (1) As litter decomposes, is remaining mass microbially-derived or undecomposable litter? (2) Are there quantitative differences in how litter decomposition varies with position, or among climates, that lead to more efficient C stabilization in soils? (3) Over time, do different types of litter converge on a similar composition due to the formation of similar microbial compounds? The answers to these questions will transform how litter decomposition is represented conceptually, and in predictive models. The current LIDET dataset is a benchmark for Earth System Models, and this project will augment it with valuable information on how litter chemical composition changes across space and time during decomposition.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

尚不清楚将富含碳的植物碎屑（枯叶，根，茎和四肢）纳入土壤中的过程。近一个世纪以来，土壤中的大多数碳被认为是基于植物的化合物，可抗微生物的分解（顽固的土壤碳假设）。最近的研究表明，微生物几乎可以分解所有植物衍生的化合物，并且土壤碳主要由它们产生的微生物和化合物组成。如果发现植物碎屑的完全分解是一种广泛的现象，它将颠覆顽固的土壤碳的范式，并且需要改变碳通量的全球模型。由于微生物产生了不同于植物碎屑的化合物，因此可以从它们留在土壤中的化学指纹中推断出微生物衍生的土壤碳的比例。 该项目将使用最先进的分析化学方法来表征从10年分解实验中存档样品（形成苔原的热带地区）的微生物指纹的程度。所得数据将用于确定植物碎屑是否在土壤中产生大量不可分解的碳，还是本质上所有植物碎屑转化为微生物生物量。这种精致的理解将增加当前的土壤碳形成概念框架，并使土壤碳形成的过程在模型中更准确地表示。该项目还将开发一个定量的教学单元，上面有关土壤碳的形成和垃圾分解建模，该模型将是开放访问权限并可以为更广泛的教育社区提供的。准确的概念模型的开发受到无法准确量化分解过程中垃圾化学变化的方法和数据的阻碍。该项目将通过量化垃圾化学的变化如何随着时间的流逝，气候和位置（以上与地下）的位置（使用固态13C-NMR）来表征来自世界上最广泛的长期长期分解实验之一（长期的间隔分解团队，遗址）来解决这个差距。具体来说，该项目将解决三个问题，目的是创建一个新的垃圾分解概念模型：（1）随着垃圾分解，仍保持大量微生物衍生或不可分解的垃圾？ （2）在垃圾分解如何随位置或气候中导致土壤中更有效的C稳定化的位置或气候之间的变化是否存在定量差异？ （3）随着时间的流逝，由于形成相似的微生物化合物，不同类型的垃圾会在类似的组合物上收敛吗？这些问题的答案将改变垃圾分解在概念上和预测模型中的表示。当前的LIDET数据集是地球系统模型的基准，该项目将通过有关分解过程中垃圾化学成分如何变化的有价值的信息来增强它。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛影响的审查标准来通过评估来支持的。