Impact of fire on active layer and permafrost microbial communities and metagenomes in an upland Alaskan boreal forest.
Permafrost soils are large reservoirs of potentially labile carbon (C). Understanding the dynamics of C release from these soils requires us to account for the impact of wildfires, which are increasing in frequency as the climate changes. Boreal wildfires contribute to global emission of greenhouse gases (GHG-CO2, CH4 and N2O) and indirectly result in the thawing of near-surface permafrost. In this study, we aimed to define the impact of fire on soil microbial communities and metabolic potential for GHG fluxes in samples collected up to 1 m depth from an upland black spruce forest near Nome Creek, Alaska. We measured geochemistry, GHG fluxes, potential soil enzyme activities and microbial community structure via 16SrRNA gene and metagenome sequencing. We found that soil moisture, C content and the potential for respiration were reduced by fire, as were microbial community diversity and metabolic potential. There were shifts in dominance of several microbial community members, including a higher abundance of candidate phylum AD3 after fire. The metagenome data showed that fire had a pervasive impact on genes involved in carbohydrate metabolism, methanogenesis and the nitrogen cycle. Although fire resulted in an immediate release of CO2 from surface soils, our results suggest that the potential for emission of GHG was ultimately reduced at all soil depths over the longer term. Because of the size of the permafrost C reservoir, these results are crucial for understanding whether fire produces a positive or negative feedback loop contributing to the global C cycle.
Department of Ecology, Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
Neslihan
N
Taş
Department of Ecology, Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
Emmanuel
E
Prestat
US Geological Survey, Menlo Park, CA, USA.
Jack W
JW
McFarland
US Geological Survey, Boulder, CO, USA.
Kimberley P
KP
Wickland
Howard Hughes Medical Institute and Departments of Chemistry and Biochemistry and Computer Science, and BioFrontiers Institute, University of Colorado, Boulder, CO, USA.
Rob
R
Knight
School of Natural Sciences, University of California Merced, Merced, CA, USA.
Asmeret Asefaw
AA
Berhe
Alaska Ecoscience, Fairbanks, AK, USA.
Torre
T
Jorgenson
US Geological Survey, Menlo Park, CA, USA.
Mark P
MP
Waldrop
1] Department of Ecology, Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA [2] Joint Genome Institute (JGI), Walnut Creek, CA, USA [3] Joint BioEnergy Institute (JBEI), Emeryville, CA, USA.
Janet K
JK
Jansson
D000413:Alaska; D044822:Biodiversity; D002244:Carbon / Q000032:analysis*; D005390:Fires; D054892:Metagenome; D065946:Permafrost / Q000737:chemistry / Q000382:microbiology*; D012988:Soil Microbiology; D066188:Taiga
D002244:Carbon