Dissertation Research: Rhizodeposition Control on Spatial Compartmentalization of Active Microorganisms and Nitrogen Mineralization/Immobilization

植物碳从根部进入土壤的运动， 这种碳对氮矿化的影响， 将研究土壤中的固定过程。 实验将使用放射性和稳定的 同位素示踪剂跟踪的运动和转换 14 CO2和5 NH 4在根室（根管）种植 黄松和雀麦。 微生物的质量和活性将是 研究的重点。 微生物的空间分布 生物量将相对于植物根来确定。 的 这些微生物的代谢状态将使用 活体染色和显微放射自显影。 氮矿化 并将使用短期15 N池确定固定化 稀释实验 这些研究的结果将用于 比较根际和非根际土壤的代谢状况 微生物，并确定微生物的重要性 土壤-根系界面对植物养分的竞争， 这些模型系统。 这个项目的重要性在于它应该产生一个 为今后就下列问题开展工作提供宝贵的数据库： 植物根部的碳和植物可利用的氮量; 也就是说，它将导致洞察力，什么控制N 土壤系统的可用性。 这是一个重要的问题，因为N 往往是生态系统中限制植物生长的养分- 宽 加州大学伯克利分校的设施， 非常适合这类研究 凡士通博士是一位 一流的科学家和教师，这个研究领域是一个 她的专长。 诺顿女士的所有证据表明 有前途的学生，有三个出版物，她的信用，甚至 在开始她的博士工作之前。

The movement of plant carbon from roots into the soil and the effects of this carbon on nitrogen mineralization and immobilization processes in the soil will be studied. Experiments will be performed using radioactive and stable isotope tracers to follow the movement and transformations of 14CO2 and 5NH4 in root chambers (rhizotrons) planted with Pinus ponderosa and Bromus mollis. The mass and activity of microorganisms will be a central focus of the research. The spatial distribution of microbial biomass will be determined in relation to plant roots. The metabolic state of these microorganisms will be assessed using vital stains and microautoradiography. Nitrogen mineralization and immobilization will be determined using short-term 15N pool dilution experiments. Results from these studies will be used to compare the metabolic status of rhizosphere and bulk soil microorganisms and to determine the importance of microbial competition for plant nutrients at the soil-root interface for these model systems. The significance of this project is that it should yield a valuable data base for future work on the relationship between plant carbon from roots and the amount of N available to plants; that is, it will lead to insight as to what controls N availability in soil systems. This is an important issue since N is often the nutrient limiting plant growth in ecosystems world- wide. The facilities at the University of California, Berkeley, are excellent for this type of research. Dr. Firestone is a first-rate scientist and teacher and this area of research is one of her specialties. Ms. Norton shows all evidence of being a promising student with three publications to her credit even before beginning her doctoral work.