Humans have dramatically altered the earth's nitrogen (N) cycle. Anthropogenic introduction of reactive N into the biosphere now exceeds natural sources of N to terrestrial ecosystems. This results in substantial negative human and environment health effects. The only process that permanently removes reactive N from the environment is denitrification (reduction, by bacteria, of reactive N to non-reactive N2 gas). Denitrification occurs in almost all terrestrial, freshwater, and marine ecosystems, but fragmentation of the science has impeded quantification of this critical process. This project will develop an international coordinated network (RCN) of denitrification scientists from a wide array of disciplines, from molecular biology to ecosystem science, and from soil science to oceanography. Through interdisciplinary exchange it will advance quantification of denitrification, and models to scale-up site specific measurements to ecosystem, regional and global scales. Mechanisms to achieve this include workshops, targeted integrative special sessions at major scientific meetings, and a website with contact information and on-line training. Broader Impacts: Interdisciplinary education of undergraduate, graduate students and post-docs is an important function of this project. It will contribute knowledge to future management of the global N cycle to meet objectives of both food security and environmental quality. Knowledge will be shared between "academic" denitrification experts and individuals who are using the denitrification process for practical applications (e.g., wastewater treatment facilities, human engineered wetlands).
