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Abstract Wildland fire is increasingly recognized as a driver of bioaerosol emissions, but the effects that smoke-emitted microbes have on the diversity and community assembly patterns of the habitats where they are deposited remain unknown. In this study, we examined whether microbes aerosolized by biomass burning smoke detectably impact the composition and function of soil sinks using lab-based mesocosm experiments. Soils either containing the native microbial community or presterilized by γ-irradiation were inundated with various doses of smoke from native tallgrass prairie grasses. Smoke-inundated, γ-irradiated soils exhibited significantly higher respiration rates than both smoke-inundated, native soils and γ-irradiated soils exposed to ambient air only. Microbial communities in γ-irradiated soils were significantly different between smoke-treated and control soils, which supports the hypothesis that wildland fire smoke can act as a dispersal agent. Community compositions differed based on smoke dose, incubation time, and soil type. Concentrations of phosphate and microbial biomass carbon and nitrogen together with pH were significant predictors of community composition. Source tracking analysis attributed smoke as contributing nearly 30% of the taxa found in smoke-inundated, γ-irradiated soils, suggesting smoke may play a role in the recovery of microbial communities in similar damaged soils. Our findings demonstrate that short-distance microbial dispersal by biomass burning smoke can influence the assembly processes of microbial communities in soils and has implications for a broad range of subjects including agriculture, restoration, plant disease, and biodiversity.
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Evidence for Wildland Fire Smoke Transport of Microbes From Terrestrial Sources to the Atmosphere and Back
Abstract Smoke from wildland fires contains more diverse, viable microbes than typical ambient air, yet little is known about the sources and sinks of smoke‐borne microorganisms. Data from molecular‐based surveys suggest that smoke‐borne microorganisms originate from material associated with the vegetation and underlying soils that becomes aerosolized during combustion, however, the sources of microbes in smoke have not yet been experimentally assessed. To elucidate this link, we studied high‐intensity forest fires in the Fishlake National Forest, Utah, USA and applied source‐sink modeling to assemblages of 16S ribosomal RNA (rRNA) gene sequences recovered from samples of smoke, vegetation, and soil. Our results suggest that 70% of the bacterial taxa in smoke originated from the local aspen (Populus tremuloides) (33%) and soil (37%) communities. In comparison, 42% of bacteria in air sampled prior to the fires could be attributed to these terrestrial sources. When the bacterial assemblages in smoke were modeled as sources to the local communities, they contributed an average of 25% to the terrestrial sinks versus an estimated contribution of <4% from ambient air. Our results provide support for the role of wildland fire in bacterial dispersal and the working hypothesis that smoke is an environmental reservoir of microbes for receiving ecosystems.
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- Award ID(s):
- 2039525
- PAR ID:
- 10599121
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Biogeosciences
- Volume:
- 129
- Issue:
- 9
- ISSN:
- 2169-8953
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Recent studies have suggested that microbial aerosolization in wildfire smoke is an understudied source of microbes to the atmosphere. Wildfire smoke can travel thousands of kilometers from its source with the potential to facilitate the transport of microbes, including microbes that can have far‐reaching impacts on human or ecosystem health. However, the relevance of longer‐range detection of microbes in smoke plumes remains undetermined, as previous studies have mainly focused on analyses of bioaerosols collected adjacent to or directly above wildfires. Therefore, we investigated whether wildfire smoke estimated to originate >30 km from different wildfire sources would contain detectable levels of bacterial and fungal DNA at ground level, hypothesizing that smoke‐impacted air would harbor greater amounts and a distinct composition of microbes as compared to ambient air. We used cultivation‐independent approaches to analyze 150 filters collected over time from three sampling locations in the western United States, of which 34 filters were determined to capture wildfire smoke events. Contrary to our hypothesis, smoke‐impacted samples harbored lower amounts of microbial DNA. Likewise, there was a limited signal in the composition of the microbial assemblages detected in smoke‐affected samples as compared to ambient air, but we did find that changes in humidity were associated with temporal variation in the composition of the bacterial and fungal bioaerosols. With our study design, we were unable to detect a robust and distinct microbial signal in ground‐level smoke originating from distant wildfires.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1029/2024JG008236
