15N Natural Abundance of Soil Microbial Biomass as a Tool for Assessing Controls on N-cycling Processes in Ecosystems

土壤微生物量的 15N 自然丰度作为评估生态系统氮循环过程控制的工具

• 批准号: 0416223
• 负责人: Egbert Schwartz
• 金额: --
• 依托单位: Northern Arizona University
• 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: 2004-08-15 至 2008-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0416223&HistoricalAwards=false
• 关键词: 15N; Natural; Abundance; Soil; Microbial

Nitrogen limits plant growth in many soils around the world. Plants compete with microorganisms in the soil for nitrogen. When carbon is abundant in the form of organic matter or dead organisms, and nitrogen is relatively scarce, the microorganisms will take up most of the available nitrogen. In contrast, when microbial growth is limited by carbon, soil microorganisms will increase the amount of nitrogen available to plants by breaking down organic matter that contains nitrogen. At present it is difficult to measure if soil microorganisms are competing with plants for nitrogen or if they are helping plants to grow by supplying nitrogen. Nitrogen atoms occur in a least two forms in the environment. Most of the atoms have 7 protons and 7 neutrons (14N) but a few atoms will consist of 7 protons and 8 neutrons (15N). Schwartz, Hungate, Hart and Dijkstra have found that soil organisms are enriched in 15N relative to nitrogen in the soil solution. They propose that the ratio of 15N to 14N in the microbial biomass indicates if microbial growth is limited by nitrogen or by carbon. If correct, it will be possible to ascertain if plant growth is promoted or restricted by soil organisms. This project will be the first to measure the stable nitrogen isotope composition of the soil microbial biomass, and to test a conceptual model for how microbial 15N enrichment is controlled. This study may provide a new tool to assay the impact of soil microorganisms on plant productivity. In addition, the project will contribute to education at undergraduate and graduate levels. The principal investigators teach courses in environmental microbiology, general ecology, microbial ecology, ecosystem ecology and forestry. The proposed research will be incorporated into these courses.

氮限制了世界上许多土壤中的植物生长。植物与土壤中的微生物争夺氮。当碳以有机物或死亡生物的形式丰富，而氮相对稀缺时，微生物会吸收大部分可用氮。相反，当微生物的生长受到碳的限制时，土壤微生物会通过分解含有氮的有机物来增加植物可利用的氮量。目前，土壤微生物是在与植物争夺氮素，还是在通过提供氮素来帮助植物生长，还很难衡量。氮原子在环境中至少以两种形式存在。大多数原子有7个质子和7个中子（14N），但少数原子将由7个质子和8个中子（15N）组成。Schwartz、Hungate、Hart和Dijkstra发现，相对于土壤溶液中的氮，土壤生物富含15N。他们提出，微生物生物量中15N与14N的比例表明微生物的生长是受到氮还是碳的限制。如果正确，就有可能确定植物的生长是受到土壤生物的促进还是限制。该项目将首次测量土壤微生物生物量的稳定氮同位素组成，并测试如何控制微生物15N富集的概念模型。本研究为研究土壤微生物对植物生产力的影响提供了一种新的工具。此外，该项目还将促进本科生和研究生的教育。主要教授环境微生物学、普通生态学、微生物生态学、生态系统生态学、林学等课程。建议的研究将纳入这些课程。