Last week, her work earned Keiser, who graduated in 2014, the fourth annual F. Herbert Bormann Prize
, an award that honors an F&ES doctoral student whose work best exemplifies the legacy of the late Yale professor.
While much of her doctoral research examined the impacts of global change on the carbon cycle through plant–soil feedbacks, the Bormann Prize committee highlighted her study, published in the journal Ecosystems
, which examined the dynamic relationship between carbon availability and nitrogen transformations. The paper was co-authored by Mark Bradford
, professor of terrestrial ecosystem ecology at F&ES, and Jennifer Knoepp
of the U.S. Forest Service.
For that study, Keiser, who is now a postdoctoral research associate at Iowa State University, spent several weeks sampling 10 sub-watersheds with different disturbance histories in the southern Appalachian Mountains. Within each sub-watershed she collected and analyzed soil samples taken from 50-meter transects covering representative gradients. Specifically, she wanted to compare an extensive set of soil and nutrient variables at the landscape scale, at low and high elevations, and between sites located near the streambed or in upload locations.
“We knew there might be many drivers influencing nitrification,” she said. “But at the watershed scale what it really all came down to was whether those sub-watersheds had been disturbed through human influence — such as clear-cutting or shifting forest types. This landscape disturbance alters the amount of soil carbon available, which in turn affected whether nitrification occurred or did not occur.”
Nitrification is the biological process in which ammonia, a form of nitrogen found in the soil, is converted into nitrate. As previous research suggests, microbes in soil where carbon is abundant require ample nitrogen to meet their metabolic needs. By consuming that nitrogen to meet their own needs, the microbial community can prevent nitrification.