Predicting Post-Fire N Cycling through Traits and Cross-Kingdom Interactions
Sydney I. Glassman1*, Steven D. Allison2, Joanne B. Emerson3, Peter M. Homyak1 and Michael J. Wilkins4
1University of California–Riverside; 2University of California–Irvine; 3University of California–Davis; and 4Colorado State University
Wildfires are increasing in frequency, size, and severity across the globe. Unlike ecosystem disturbances that primarily impact vegetation, wildfires kill microbes, thereby dramatically altering the composition, function, and abundance of post-fire soil microbiomes, with downstream impacts on soil nitrogen (N) cycling. Despite widespread microbial mortality during fires, post-fire environments can also favor the growth of pyrophilous fire-loving microbes. Pyrophilous microbes have been documented in widespread post-fire habitats, yet their traits and impacts on ecosystem N losses remain largely uncharacterized. Here, researchers focus on how wildfire severity and pyrophilous microbial interactions regulate N cycling and the emission of greenhouse gasses (GHG) like nitrous oxide, a powerful greenhouse gas with 300x the warming potential of carbon dioxide, with implications for long-term ecosystem recovery, regional air quality, and Earth’s climate. The overarching project goal is to answer the question: Do conserved genomic traits and cross-kingdom interactions drive post-fire N cycling across ecosystems?
Understanding how microbial interactions and their traits govern N cycling is critical to forecasting post-fire soil N dynamics and ecosystem recovery. Using pyrophilous microbiomes as model systems, the team will scale up across systems of increasing complexity, from individual genomes to more complex microbiomes to predict the impacts of wildfire disturbance on ecosystem N cycling with the DEcomposition Model of ENzymatic Traits (DEMENT). Across three ecosystems that are experiencing increased fire frequency (Mediterranean grasslands, chaparral shrublands, montane coniferous forests) the team asks: 1) How do microbial traits change during post-fire succession? 2) How does fire severity influence microbial succession and gene expression of N cycling functions? 3) How do cross-kingdom interactions change during post-fire succession? 4) How do traits and interactions affect ecosystem N fates and cycling?
To answer these questions, the team will 1) identify putative pyrophilous traits across microbiota and biomes and cross-kingdom interactions among archaea, bacteria, fungi, and viruses that affect N cycling genes and biogeochemistry using metagenomic datasets and culture-and microcosm-based assays; 2) test and refine the trait predictions by coupling microbiomes and N cycling genes to N biogeochemistry via experimental pyrocosms to simulate soil heating under controlled and replicable conditions; and 3) scale up microbial traits and interactions to the ecosystem level by integrating the measurements with the trait-based DEMENT model. Microbiological insights assessed via genomics, metagenomics, metatranscriptomics, and viromics will be paired with biogeochemical approaches that combine traditional laboratory assays with isotopic approaches to track the production and consumption of substrates involved in GHG emissions. Experimental approaches and modeling will span microbial domains (archaea, bacteria, fungi, and viruses) and diverse fire-impacted ecosystems (Mediterranean grasslands, chaparral shrublands, and montane coniferous forests) to assess the generality of the results at broad spatial and temporal scales.
This research was supported by the DOE Office of Science, Office of Biological and Environmental Research (BER), grant no. DE-SC0023127.