"Dissertation Research: "Anaerobic ammonium oxidation:a new pathway for N2 losses from humid tropical forest soils?"

反硝化为一氧化二氮(N2O)和氮素(N2)是陆地氮(N)循环中最鲜为人知的部分之一。这种微生物过程可以将N以N2O的形式释放到大气中，N2O是一种强有力的温室气体，也是平流层臭氧消耗的催化剂，或者是一种惰性气体。热带雨林土壤是全球最大的N2O天然来源之一，本论文的研究重点在于了解热带雨林土壤对氮气和N2O反硝化作用的控制。在初步实验中，检测到厌氧氨氧化(Anammox)产生氮气的证据，以及铁还原与厌氧氨氧化和反硝化耦合的证据。这些新途径的出现可能会改变人们对生态系统规模氮循环的普遍理解。这项研究将确定这些新的氮气产生途径在旱地土壤中的意义。这将通过使用15-N示踪方法的实验室实验来实现，这些方法类似于那些成功地用来表明Anammox在海洋环境中的重要性的方法。该项目将包括在当地社区和加州大学伯克利分校校园开展的几项科学外展活动。其中包括对Techbridge Girls的积极贡献，这是一个向女孩介绍技术、科学和工程职业的当地项目，以及社区科学资源，帮助小学教师将科学资源用于实践课堂活动。在加州大学伯克利分校，项目人员将参加本科生研究生导师计划。研究成果将在国家科学会议上传播，并纳入加州大学伯克利分校关于N自行车的生态系统生态学讲座。

Denitrification to nitrous oxide (N2O) and dinitrogen (N2) is one of the most poorly understood portions of the land-based nitrogen (N) cycle. This microbial process can release N to the atmosphere as N2O, a potent greenhouse gas and a catalyst for stratospheric ozone depletion, or N2, an inert gas. This dissertation research focuses on understanding the controls on denitrification to N2 and N2O in tropical forest soils, one of the largest natural sources of N2O globally. In preliminary experiments, evidence of N2 production from anaerobic ammonium oxidation (anammox) was detected, as was evidence of iron reduction coupled to anaerobic ammonium oxidation and denitrification. The presence of these new pathways is likely to change the general understanding of ecosystem-scale N cycling. This research will determine the significance of these new N2 production pathways in upland soils. This will be achieved with laboratory experiments employing 15-N tracer methods similar to those successfully used to show the importance of anammox in marine environments. This project will include several science outreach activities in the local community and on the UC-Berkeley campus. These include active contributions to Techbridge Girls, a local program introducing girls to careers in technology, science and engineering, and Community Resources for Science, which helps elementary school teachers use scientific resources for hands-on classroom activities. At UC-Berkeley, project personnel will participate in the Undergraduate Graduate Mentorship Program. Research results will be disseminated at national scientific conferences and incorporated into Ecosystem Ecology lectures on N cycling at UC-Berkeley.