Gaseous nitrogen fluxes in dry soils: are surviving microbes controlling nitrogen emissions?
Soil gaseous nitrogen (N) emissions are not typically considered in ecosystem N budgets, presumably because in mesic sites, hydrologic N losses balance N inputs. However, in dryland environments, significant amounts of N are exported through gaseous pathways, yet the mechanisms controlling fluxes are poorly understood. In particular, are microbes controlling N emissions in dry soil? Does soil rewetting hinder microbial activity while enhancing abiotic processes? Paradoxically, biological control of N emissions appears to intensify during soil drying and becomes less important during soil rewetting. Because dryland regions comprise about 1/3 of the land surface and account for 25% of soil NO emissions, understanding what processes control N losses is critical for developing nutrient budgets and modeling N pollution. This research seeks to transform understanding of N cycling by evaluating two widely held paradigms: 1) that in dry soil, biological cycling of N is unimportant and 2) that N emissions are not significant in annual N budgets.
The training objectives are to broaden knowledge in soil C and N cycling, learn the application of eddy covariance, develop a method for measuring the isotopic composition of oxygen in NO. Broader impacts include land management applications to establish N critical loads in ecosystems impacted by N pollution through vegetation type conversions and increased incidence of wildfires. This research will also be used to foster participation of underrepresented groups in science and mathematics by delivering lesson plans through the PUENTE program, the "Outdoor Classroom" at Sedgwick Reserve, and Scienceline, a website that partners scientists with K-12 students.
