Dissertation Research: Does microbial diversity affect ecosystem function? : A denitrification case study

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Human activities have more than doubled nitrogen pollution of the environment through the use of agricultural fertilizer and deposition from fossil fuel burning. This has important ecological consequences, yet the fate of nitrogen in ecosystems is poorly understood. Previous work on nitrogen budgets have found that a large fraction of added nitrogen cannot be accounted for. One of the ways this nitrogen might not show up in the budget is if it is converted to a gas. This can occur through a process called denitrification, which creates harmless dinitrogen gas (N2). However, this pathway can release harmful intermediates, such as nitrite, nitric oxide and nitrous oxide, with the latter being a potent greenhouse gas. Therefore, understanding the factors controlling the rate of leakage, which could include the nature of the microbial community or the soil properties, is important if we are to have an accurate understanding of the fate of nitrogen added to soil systems. One of the challenges faced in doing this type of work is quantifying denitrification intermediates and, especially, N2, since it is difficult to distinguish the N2 produced from denitrification from that present in the atmosphere. The work proposed here will take advantage of a novel sampling robot that can measure and quantify the production of all intermediates and N2 from soils. In addition to measuring intermediate release we will identify the active bacterial communities responsible for denitrification through sequencing of the active genes. By taking a two-pronged approach we can more accurately define the factors controlling nitrogen flow in ecosystems.This project will explore the relationship between the active soil microbial community and rates of denitrification, an essential ecosystem process which has implications on global climate change. Data collected from this research will strengthen interdisciplinary research that involves the fields of microbiology, ecology, biogeochemistry and bioinformatics. The microbial sequencing data will be made publicly available, and the data will be especially useful for the development of undergraduate classroom materials for bioinformatics training at both the introductory and advanced level. This project will also foster training of undergraduate students in microbiology and biogeochemical sciences. Finally, this project will support international collaborations with soil microbial ecologists in Norway.