CAREER: Understanding Nitrogen Limitation of Decomposition

职业：了解氮的分解限制

• 批准号: 0347103
• 负责人: Sarah Hobbie
• 金额: $ 50万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-05-15 至 2010-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0347103&HistoricalAwards=false
• 关键词: CAREER; Understanding; Nitrogen; Limitation; Decomposition

Nitrogen (N) produced by modern agriculture and fossil fuel combustion can be transported downwind from agricultural or industrial areas and deposited on ecosystems that historically may have experienced low levels of N inputs. Although N is an important nutrient required by both plants and soil organisms, it is presently unknown how these elevated inputs of N will affect decomposition of organic matter. Because decomposition is the primary way that carbon taken up by plants during photosynthesis is ultimately returned to the atmosphere as carbon dioxide (CO2), understanding effects of N on decomposition is necessary for predicting future human impacts on atmospheric concentrations of CO2. Recent work showed that in low-N sites, plant detritus (litter) with a greater N content decomposed more quickly, suggesting that decomposing microorganisms require N to break down plant litter. However, addition of inorganic N fertilizer increased decomposition in only two of eight sites. These paradoxical results call into question the assumption that the often-observed positive relationship between litter N concentration and decomposition arises because N limits decomposition. The proposed research will use both mathematical models and field experiments to clarify how N affects decomposition, focusing on N effects on the soil microorganisms responsible for the process of decomposition. This specific research goal fits into the investigator's broader objective for the proposed research and education plan to develop new skills and approaches for more effective pursuit of research and education of students and the public in fundamental questions in ecosystem ecology that have applications to global environmental change. The research will involve a 4-y study at the Cedar Creek Natural History Area, Minnesota, in which the amount and form of N supplied to decomposers will be experimentally controlled. The response of the microbial community will be monitored. In addition, mathematical models will be developed to explore the consequences of variation in decomposition rate. Proposed educational activities include involving undergraduates in research, developing two new courses, enhancing an existing course, and developing effective public outreach skills with the aim of improving literacy regarding global environmental change. The proposed research and education plan will achieve broader impacts by increasing understanding of how atmospheric N deposition alters carbon cycling in ecosystems; through development of mathematical models of N effects on decomposition; through the development of a faculty member's skills in theoretical and microbial techniques; through the development of two courses (one undergraduate, one graduate) to educate students in environmental science and the science and policy of global change; through enhancement of an existing course via incorporation of active-learning techniques; through support and mentorship of a minority graduate student; and through support and mentorship of three undergraduates in research via an existing program that has successfully recruited participants from underrepresented groups.

现代农业和化石燃料燃烧生产的氮（N）可以从农业或工业区下风，并沉积在历史上可能经历了低水平的N投入的生态系统上。 尽管N是植物和土壤生物所需的重要营养素，但目前尚不清楚这些升高的N输入将如何影响有机物的分解。 由于分解是二氧化碳（CO2）在光合作用过程中植物吸收的碳的主要方式，因此理解N对分解的影响对于预测未来人类对人类对二氧化碳大气浓度的影响是必要的。最近的工作表明，在低N地点，植物碎屑（垃圾）更快地分解了N含量，这表明分解微生物需要N分解植物垃圾。 但是，在八个地点中，添加无机N肥料增加了分解。 这些自相矛盾的结果质疑以下假设：由于n限制了分解，因此出现了垃圾N浓度和分解之间经常观察到的正相关关系。拟议的研究将使用数学模型和现场实验来阐明氮如何影响分解，重点关注N对负责分解过程的土壤微生物的影响。这个具体的研究目标符合研究者对拟议的研究和教育计划的更广泛的目标，旨在开发新技能和方法，以更有效地追求学生和公众对生态系统生态学的基本问题的研究和教育，这些问题适用于全球环境变化。 这项研究将涉及明尼苏达州的Cedar Creek自然历史区的4-Y研究，其中供应给分解剂的N的数量和形式将受到实验控制。 将监控微生物群落的反应。 此外，将开发数学模型来探索分解速率变化的后果。 拟议的教育活动包括让大学生参与研究，开发两个新课程，增强现有课程以及开发有效的公共外展技能，以改善有关全球环境变化的识字率。 拟议的研究和教育计划将通过对大气n沉积如何改变生态系统中的碳循环方式来实现更广泛的影响。通过开发n影响分解的数学模型；通过发展理论和微生物技术方面的教师技能；通过开发两门课程（一门本科生，一名毕业生），以教育学生有关环境科学的教育以及全球变化的科学与政策；通过纳入主动学习技术来增强现有课程；通过少数研究生的支持和指导；通过现有计划在研究中的三名大学生的支持和指导，该计划成功地招募了代表性不足的群体的参与者。