The impact of wildfire on microbial C:N:P stoichiometry and the fungal-to-bacterial ratio in permafrost soil
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CitationZhou, Xuan. Sun, Hui. Pumpanen, Jukka. Sietiö, Outi-Maaria. Heinonsalo, Jussi. Köster, Kajar. Berninger, Frank. (2018). The impact of wildfire on microbial C:N:P stoichiometry and the fungal-to-bacterial ratio in permafrost soil. BIOGEOCHEMISTRY, [First Online: 28 October 2018], 1-17. 10.1007/s10533-018-0510-6.
Wildfires thaw near-surface permafrost soils in the boreal forest, making previously frozen organic matter available to microbes. The short-term microbial stoichiometric dynamics following a wildfire are critical to understanding the soil element variations in thawing permafrost. Thus, we selected a boreal wildfire chronosequence in a region of continuous permafrost, where the last wildfire occurred 3, 25, 46, and > 100 years ago (set as the control) to explore the impact of wildfire on the soil chemistry, soil microbial stoichiometry, and the fungal-to-bacterial gene ratio (F:B ratio). We observed the microbial biomass C:N:P ratio remained constant in distinct age classes indicating that microbes are homeostatic in relation to stoichiometric ratios. The microbial C:N ratios were independent of the shifts in the fungal-to-bacterial ratio when C:N exceeded 12. Wildfire-induced reduction in vegetation biomass positively affected the fungal, but not the bacterial, gene copy number. The decline in microbial biomass C, N, and P following a fire, primarily resulted from a lack of soil available C and nutrients. Wildfire affected neither the microbial biomass nor the F:B ratios at a soil depth of 30 cm. We conclude that microbial stoichiometry does not always respond to changes in the fungal-to-bacterial ratio and that wildfire-induced permafrost thawing does not accelerate microbial respiration.