Interaction of Soil Nitrogen and Water Cycles Control Trace N-Gas Production

本文将研究不同干湿季节系统中一氧化氮（NO）和氧化亚氮（N20）产生的时间变化的控制因素。更具体地说，研究人员将研究：1)干燥土壤中无机氮和无机氮生产的生物和非生物过程；2)干燥土壤湿润时微量氮气冲刷的成因；3)土壤水分和基质有效性变化下硝化种群动态；4)硝化剂和反硝化剂生产一氧化氮的来源和控制；5)影响土壤N0和N20逸出的因素。这些研究将对取自三个西海岸生态系统的土壤进行，这些生态系统是加利福尼亚的橡树草地和针叶林生态系统以及墨西哥的落叶森林。将使用最先进的技术来研究土壤和微生物种群中的氮循环。其中包括氮循环工作中的15N同位素稀释技术和微生物种群工作中的荧光抗体和微放射自显影技术。过程级研究的各个方面最终将通过建模进行整合。本研究的意义在于，它将帮助我们了解土壤含水量的变化如何影响两种重要的微量气体N0和N20的产生。一氧化氮之所以引起人们的兴趣，是因为它参与了对流层的反应，而对流层的反应除其他外，会产生臭氧，臭氧是低层大气中的一种主要污染物。一氧化二氮之所以引人关注，是因为它是一种高效的温室气体，因此与全球气候变化有关。费尔斯通博士在复杂的土壤氮动态领域的生产力工作方面有着非常好的记录。她能得到的机构支持是优越的。

The factors controlling temporal variations of nitric oxide (NO) and nitrous oxide (N20) production in several systems with distinct wet and dry seasons will be investigated. More specifically, the researchers will examine: 1) biotic and abiotic processes of inorganic-N and N0 production in dry soil; 2) the origin of trace N-gas flushes when dry soils are wetted; 3) dynamics of nitrifying populations under changing soil moisture and substrate availability; 4) origin and control of N0 production by nitrifiers and denitrifiers; and 5) factors affecting escape of N0 and N20 from soil. These studies will be carried out on soils taken from three west-coast ecosystems - the oak-grasslands and coniferous forest ecosystems of California and the deciduous forests of Mexico. State-of-the-art techniques for studying nitrogen cycling in soils and microbial populations will be used. These include 15N isotope dilution techniques in the nitrogen cycling work and fluorescent antibody and micro-autoradiography techniques in the microbial population work. Various aspects of the process-level research will ultimately be integrated through modeling. The significance of this research is that it will help us to understand how changes in soil moisture content affect the production of two important trace gases, N0 and N20. Nitric oxide is of interest because of its involvement in tropospheric reactions which, among other things, create ozone, a major pollutant in the lower atmosphere. Nitrous oxide is of interest because it is a highly efficient greenhouse gas and so is involved in global climate change. Dr. Firestone has a very good record of productivity working in the complex area of soil-N dynamics. The institutional support available to her is superior.