DISSERTATION RESEARCH: Where Plant Litter Ends and Soil Carbon Begins: The Role of Microbial Physiology in Stabilizing Soil Organic Matter

论文研究：植物凋落物结束和土壤碳开始的地方：微生物生理学在稳定土壤有机质中的作用

• 批准号: 1701652
• 负责人: Richard Phillips
• 金额: $ 2.03万
• 依托单位: Indiana University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-06-15 至 2019-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1701652&HistoricalAwards=false
• 关键词: DISSERTATION; RESEARCH; Where; Plant; Litter

More carbon is found in soils than that in the atmosphere and plant life combined. It has long been assumed that the carbon stored in soil represents the "leftovers" - plant-derived compounds that cannot be broken down any further by soil microorganisms. Recent work has shown that, as soil microorganisms decompose plant materials, they can produce compounds that increase carbon storage in soil. Thus, soil microorganisms are important to both the breakdown and the buildup of soil carbon. Many questions, however, remain unanswered. What controls microbial growth, and which aspects of microbial growth should lead to long-term soil carbon storage? These are the questions to be addressed by research through this Doctoral Dissertation Improvement Grant. Experiments will make use of a novel technique to measure rates of microbial production in both a controlled laboratory experiment, and through studies along natural environmental gradients in forests. Results of this project will further our understanding of soil carbon content, and will enhance our ability to predict when and where carbon storage in soils should be greatest. The investigators will work with high school teachers to develop lesson plans and course materials, as well as with high school students directly, to provide training centered around the project objectives. The conversion of organic inputs into microbial products is fundamentally controlled by three processes: microbial growth rate, microbial growth efficiency, and microbial turnover rate. Yet, despite the theoretical importance of these parameters for stable soil organic matter (SOM) formation, little is known about how these parameters vary with resource availability and environmental conditions, and which of these parameters most strongly controls SOM dynamics. This research will address two questions: 1) How do litter quality and soil properties affect microbial growth rate, efficiency, and turnover? 2) To what extent do changes in these parameters influence SOM formation and soil carbon storage? To date, our understanding of microbial growth physiology has been hindered by the inability of common methods to quantify growth on realistic substrates. To overcome this challenge, the researchers will use a new, substrate-independent method - tracking 18O-labeled water into microbial DNA - to quantify microbial growth parameters in temperate forest soils. First, microbial growth rate, efficiency, and turnover will be quantified across natural gradients of resource availability in six temperate forests in order to determine whether these parameters are consistent with previously-collected SOM data from these same sites. Then, using two isotopically labeled litter decay experiments, the importance of litter quality versus soil properties in controlling microbial growth parameters and the conversion of plant inputs into stable SOM will be evaluated.

土壤中的碳含量比大气和植物中的碳含量总和还要多。长期以来，人们一直认为土壤中储存的碳代表着“剩余物”——来自植物的化合物，不能被土壤微生物进一步分解。最近的研究表明，当土壤微生物分解植物材料时，它们可以产生增加土壤碳储存的化合物。因此，土壤微生物对于土壤碳的分解和积累都很重要。然而，许多问题仍未得到解答。 什么控制着微生物的生长，微生物生长的哪些方面应导致土壤长期碳储存？这些是通过这项博士论文改进补助金进行研究要解决的问题。实验将利用一种新技术来测量受控实验室实验和森林自然环境梯度研究中微生物的生产率。该项目的结果将进一步加深我们对土壤碳含量的了解，并将增强我们预测土壤碳储存何时何地达到最大的能力。调查人员将与高中教师合作制定课程计划和课程材料，并直接与高中生合作，提供围绕项目目标的培训。有机投入转化为微生物产品从根本上受三个过程控制：微生物生长速率、微生物生长效率和微生物周转率。然而，尽管这些参数对于稳定的土壤有机质 (SOM) 形成具有理论上的重要性，但人们对这些参数如何随资源可用性和环境条件而变化，以及这些参数中哪一个最有力地控制 SOM 动态知之甚少。这项研究将解决两个问题：1）凋落物质量和土壤特性如何影响微生物的生长速度、效率和周转？ 2）这些参数的变化在多大程度上影响SOM的形成和土壤碳储存？迄今为止，我们对微生物生长生理学的理解一直受到阻碍，因为常用方法无法量化现实基质上的生长。为了克服这一挑战，研究人员将使用一种新的、不依赖于基质的方法——将 18O 标记的水追踪到微生物 DNA 中——来量化温带森林土壤中的微生物生长参数。首先，将在六个温带森林的资源可用性自然梯度中量化微生物生长率、效率和周转率，以确定这些参数是否与先前从这些相同地点收集的 SOM 数据一致。然后，使用两个同位素标记的凋落物腐烂实验，评估凋落物质量与土壤特性在控制微生物生长参数和将植物投入转化为稳定的 SOM 方面的重要性。