Nitrogen is a key nutrient to microbes, plants and animals, and considerable research has been directed at understanding the controls on it's retention and loss in terrestrial ecosystems. Despite this effort, much uncertainty remains, especially with regard to gaseous nitrogen losses. This is particularly troubling in the context of human modification of the nitrogen cycle, which is dramatically increasing nitrogen pollution, runoff, and the emission of nitrous oxide, a radiatively important greenhouse gas. This research will contribute to our understanding of the terrestrial nitrogen cycle by quantifying the role of "Feammox", a newly discovered pathway in the global nitrogen cycle. Feammox is the anaerobic oxidation of ammonium coupled to ferric iron [Fe (III)] reduction. It has the potential to produce inert dinitrogen gas as well as reactive nitrite, which could subsequently be reduced to gaseous or organic nitrogen, or ammonium under anaerobic conditions. Given the potential gaseous loss of nitrogen from terrestrial environments, this pathway may play a significant role in the global nitrogen cycle. The proposed research will place this newly discovered nitrogen transformation pathway in the context of the larger nitrogen cycle by (i) determining if Feammox is mediated by soil microbes, and if so identify the responsible organisms, (ii) determining the relative importance of iron- and nitrogen-containing compounds as controls on Feammox, and (iii) quantifying the role of Feammox in total nitrogen gas emissions from soils.
The collaborative research between a soil biogeochemistry laboratory at the University of California at Berkeley and a microbial biogeochemistry laboratory at the University of Nebraska, Lincoln will improve the mechanistic understanding of terrestrial nitrogen cycling. Field work will take place at the Luquillo Long Term Ecological Research site in Puerto Rico. The research addresses a previously unquantified pathway in terrestrial ecosystems that not only has implications for nutrient retention in soils, but could also evolve nitrous oxide, a greenhouse gas implicated in global change. This project will support for an early career female scientist, two graduate students, one undergraduate student, and one postdoctoral researcher. In concert with sample collection in Puerto Rico workshops and training activities will be held for Puerto Rican high school students. Science cafes in Puerto Rico and California will provide an ecology and global change educational outreach component to the public at large.
