CAREER: An integrated study of the effects of nutrient additions on grassland soil microbial communities

由于人类活动的影响，地球仪的陆地生态系统正在接受大量的氮（N）和磷（P）输入。生活在土壤中的微生物可能会对这些增加的营养投入做出反应，这种反应可能对生态系统产生深远的影响，因为土壤微生物在维持生态系统健康和生产力方面发挥着关键作用。然而，微生物群落的整体结构和多样性如何被营养添加物改变，以及微生物的反应是否反映植物的反应，目前还不清楚。为了填补这些知识空白，将从世界各地的35个草原收集土壤，这些草原已经标准化，将比较代表广泛土壤和场地特征的这些草原上的微生物和植物对养分添加的反应，以建立对微生物对养分添加的反应的更全面的理解，而不是专注于只有一个或几个站点。一系列的实验室实验，以辨别可能是负责在现场观察到的微生物的反应的具体机制也将进行，拟议的工作是创新的，它利用了最近开发的焦磷酸测序方法和基于微生物的社区分析方法，以产生一个更全面的调查土壤微生物对养分添加的反应比以往任何研究。这项研究的结果将导致一个预测性的，机械的理解土壤微生物对养分有效性变化的反应，它将提高草原生态系统地下微生物群落结构的因素的基本理解。由于草原是地球上分布最广、生产力最高的生态系统类型之一，了解草原的结构和功能如何因人类活动（即化石燃料燃烧和农业肥料的使用）造成的氮和磷负荷升高而发生变化至关重要。需要更好地了解微生物如何对这些养分输入做出反应，因为土壤微生物在维持土壤肥力，陆地碳循环和生态系统的整体健康方面发挥着关键作用。将通过几项重要的教育和推广活动，交流和研究这项工作的成果、方法和概念。(1)为美国和国际研究生开办了为期两周的“动手”暑期培训课程，重点是利用分子方法评估土壤微生物多样性。该课程将全面介绍用于调查微生物生物多样性的工具和方法，同时促进美国内外下一代研究人员之间的合作。(2)开发一系列“土壤生态学”学习活动，向参加课后数学，工程和科学成就（梅萨）计划的当地中学生介绍地下生物群的多样性和土壤生物在生态系统中的重要性。(3)指导和培训研究生和本科生谁将直接参与研究项目在未来5年。

Terrestrial ecosystems across the globe are receiving elevated inputs of nitrogen (N) and phosphorus (P) due to human activities. The microbes that live in soil are likely to respond to these elevated nutrient inputs and such responses could have far-reaching effects on ecosystems given that soil microbes play critical roles in the maintenance of ecosystem health and productivity. However, how the overall structure and diversity of microbial communities may be altered by nutrient additions, and whether microbial responses mirror plant responses, are not yet known. To address these knowledge gaps, soils will be collected from 35 grasslands throughout the world that have been receiving standardized, experimental additions of N and P. The microbial and plant responses to nutrient additions across these grasslands that represent a broad range of soil and site characteristics will be compared to build a more comprehensive understanding of microbial responses to nutrient additions than would be possible by focusing on just a single site or a handful of sites. A series of laboratory experiments to discern the specific mechanisms that may be responsible for the microbial responses observed in the field will also be conducted.The proposed work is innovative in that it takes advantage of recently-developed pyrosequencing methods and phylogeny-based community analysis approaches to yield a far more comprehensive inquiry into soil microbial responses to nutrient additions than any previous study. Results of this study will lead to a predictive, mechanistic understanding of soil microbial responses to changes in nutrient availability and it will improve fundamental understanding of the factors structuring belowground microbial communities in grassland ecosystems. Since grasslands are one of the most widespread and productive ecosystem types on Earth, understanding how the structure and function of grasslands may change in response to elevated loadings of N and P from human activities (namely fossil fuel combustion and the use of agricultural fertilizers) is of critical importance. Better understanding of how microbes will respond to these nutrient inputs is needed because soil microbes play key roles in the maintenance of soil fertility, the terrestrial carbon cycle, and the overall health of ecosystems. The results, methods, and concepts to be developed from this work will be communicated and investigated through several key educational and outreach activities. (1) The initiation of a "hands-on", 2-week summer training course for U.S. and international graduate students focused on the use of molecular methods to assess soil microbial diversity. The course will provide a comprehensive introduction to the tools and approaches used to survey microbial biodiversity while fostering collaborations among the next generation of researchers inside and outside of the United States. (2) The development of a series of 'soil ecology' learning activities to introduce local middle-school students participating in the after-school Math, Engineering, and Science Achievement (MESA) program for students underrepresented in science and technology careers to the diversity of belowground biota and the importance of soil organisms in ecosystems. (3) The mentoring and training of graduate and undergraduate students who will be directly involved in the research project over the next 5 years.