Do microbe-mineral interactions influence nitrogen cycle dynamics?

The majority of organic nitrogen in soil is often held in the mineral-associated organic matter (MAOM) fraction, which has slow turnover rates and is thought to be largely inaccessible to microbes and plants. Partially decomposed plant material forms the particulate organic matter (POM) fraction, which typically holds a smaller proportion of total organic nitrogen. Thus, MAOM can be viewed as a bottleneck to nitrogen availability within the rhizosphere, with mineralization rates depending on organic matter structure and its interaction with soil minerals and microbial communities.

This project explores how ecosystem-microbe-mineral relationships influence soil nitrogen oxide emissions. While nitrous oxide fluxes are well-documented, reactive nitrogen oxide fluxes remain understudied due to their high reactivity. This knowledge gap limits our ability to predict air quality and climate impacts of soil nitrogen emissions. We will uncover factors determining nitrogen oxide fluxes in natural ecosystems (primarily woodlands and grasslands) by combining field experiments with advanced analytical capabilities and metagenomic analyses.

We hypothesize that nitrogen oxide emissions are governed by three key factors: the activities of soil microbes that vary depending on the ecosystem, the proportion of POM and MAOM, and the underlying soil mineralogy. To test our hypothesis, we will determine the relationship between soil mineralogy and soil organic matter composition on soil outgassing of nitrogen oxides in field experiments. Additionally, we will investigate how SOM-mineral interactions affect nitrogen availability and mineralization rates in different soil fractions and ecosystems. Finally, we will identify which soil fractions are targeted by nitrogen-mining microbes and which taxa produce the enzymes needed to mobilize nitrogen in those fractions.