Understanding Microbial Control On The Fate Of Ash-Derived Carbon And Nitrogen After Prescribed Fires

Project Lead: Katie Huy

Fires, both prescribed and wild, both alter and deposit significant amounts of carbon and nitrogen into soils via ash, yet the fate of these nutrients post-fire remains poorly understood. We investigate the transformations to C/N during burning, how they influence C/N retention versus loss, and the timescales over which they occur. As microbial organisms drive both C degradation and N transformations in the soil, and are themselves impacted by the burning as well, we also investigate post-fire microbial community assembly patterns and how shifts in composition and activity may regulate geochemical changes. We sample soils exposed to varied prescribed burning methods (e.g. pile burning, broadcast burning) and within different ecosystems (e.g. chamise chaparral, coastal live oak woodland, mixed-conifer forest). We use field-based gas measurements, laboratory analyses, genomic tools, and lab-incubations to measure soil C/N pools (TOC/TN), pathways of loss (NO3, CO2/N2O), community composition (16S rRNA), and depositional environment (mineralogy, texture, moisture) over time to understand these mechanisms across scales. Ultimately, our work seeks to clarify the role of microbial community structure and depositional environment on mediating post-fire geochemical transformations– offering insights to guide burning practices and improve predictions of nutrient cycling and recovery trajectories.

Previous Interns:

Tiffany Chen (Stanford Young Investigators, 2024)

Kiara Fufunan (Stanford Earth Systems Undergraduate, 2024)