Abstract

Microbial communities regulate soil biogeochemical cycles and mediate nutrient cycling in ecosystems, and their responses and recovery following disturbance influences ecosystem resilience and recovery. Wildfire disturbance directly shifts microbial community structure as well as soil physical and chemical characteristics. Wildfires are increasing in size and severity across the western United States where burn severity depends on factors such as vegetation type and biomass, landscape structure, depth and hydrologic conditions. This study investigates microbial community successional dynamics in a catchment within the Jemez River Basin Critical Zone Observatory that had experienced a mixed-severity wildfire in June 2013. The site is being characterized in the context of broader microbial community data (e.g., exoenzyme assays, microbial cell counts and biomass, and 16S and ITS rRNA gene amplicon sequencing as well as geochemical data (e.g., organic carbon, total nitrogen, pH, gravimetric water content and concentration of base anions and cations). We sampled 22 sites along a topographic gradient 18 days after the wildfire was contained and over the following two years at six discrete depth increments from 0-40 cm depth. Wildfire altered organic substrate quality, biomass, community structure and shifts in exoenzyme activity. Increased soil pH was associated with burn severity and is a commonly attributed explanatory variable describing microbial community structure. We found shifts in exoenzyme activities from carbon to nitrogen-dominated and are linking these to microbial taxa and function.

Citation

Fairbanks, D., Muscarella, C.R., Murphy, M.A., Chorover, J., Rich, V.I., Gallery, R.E. (2018): Soil biogeochemistry and microbial community recovery post-wildfire in a mixed conifer forest in northern New Mexico. Abstract B42D-05 presented at 2018 AGU Fall Meeting, Washington, D.C., 10-14 Dec.