| 1. |
- Juottonen, Heli, et al.
(author)
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Microform-related community patterns of methane-cycling microbes in boreal Sphagnum bogs are site specific
- 2015
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In: FEMS Microbiology Ecology. - : Oxford University Press (OUP). - 0168-6496 .- 1574-6941. ; 91:9
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Journal article (peer-reviewed)abstract
- Vegetation and water table are important regulators of methane emission in peatlands. Microform variation encompasses these factors in small-scale topographic gradients of dry hummocks, intermediate lawns and wet hollows. We examined methane production and oxidization among microforms in four boreal bogs that showed more variation of vegetation within a bog with microform than between the bogs. Potential methane production was low and differed among bogs but not consistently with microform. Methane oxidation followed water table position with microform, showing higher rates closer to surface in lawns and hollows than in hummocks. Methanogen community, analysed by mcrA terminal restriction fragment length polymorphism and dominated by Methanoregulaceae or ‘Methanoflorentaceae’, varied strongly with bog. The extent of microform-related variation of methanogens depended on the bog. Methanotrophs identified as Methylocystis spp. in pmoA denaturing gradient gel electrophoresis similarly showed effect of bog, and microform patterns were stronger within individual bogs. Our results suggest that methane-cycling microbes in boreal Sphagnum bogs with seemingly uniform environmental conditions may show strong site-dependent variation. The bog-intrinsic factor may be related to carbon availability but contrary to expectations appears to be unrelated to current surface vegetation, calling attention to the origin of carbon substrates for microbes in bogs.
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| 2. |
- Peltoniemi, Krista, et al.
(author)
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Responses of methanogenic and methanotrophic communities to warming in varying moisture regimes of two boreal fens
- 2016
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In: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717 .- 1879-3428. ; 97, s. 144-156
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Journal article (peer-reviewed)abstract
- Peatlands are one of the major sources of the powerful greenhouse gas methane (CH4). Our aim was to detect responses of methanogenic archaeal and methane-oxidizing bacterial (MOB) communities that control the methane (CH4) cycle to climatic warming. This study took place in two boreal fens three years after experimental warming in un-manipulated wet and drier regimes, thus simulating future climate scenarios. We determined active methanogen and MOB communities as transcripts of mcrA and pmoAgenes, along with the abundance of these genes, CH4 production and oxidation potentials, and in situ CH4 fluxes. Methanogenic community remained similar, although methanogen abundance decreased after warming. In the wet regime, this decrease resulted in a small but significant reduction on the potential CH4 production in such peat layers where the average production potential was high. Drying alone, however, reduced the potential CH4 production more than warming, and this impact was strong enough to mask the small warming impact in the drier regime. Warming did not affect the MOB community or the potential CH4 oxidation in the wet regime; however, type Ib MOB abundance decreased and MOB related to genus Methylocapsa became typical after warming in the drier regime of the southern fen. The in situ measured CH4 fluxes indicated similar patterns as potential measurements; both warming and drying reduced methane emissions, drying more than warming. These results indicate that methanogens and MOB may have different controlling patterns on CH4 fluxes when facing global warming. These patterns may further differ not only between moisture regimes, but inside the same habitat type, here boreal fen. Irrespective of this variation, the in situ CH4 fluxes still seem to respond similarly across sites.
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| 3. |
- Pennanen, Taina, et al.
(author)
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Structure of a microbial community in soil after prolonged addition of low levels of simulated acid rain
- 1998
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In: Applied and Environmental Microbiology. - 0099-2240. ; 64:6, s. 2173-2180
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Journal article (peer-reviewed)abstract
- Humus samples were collected 12 growing seasons after the start of a simulated acid rain experiment situated in the subarctic environment. The acid rain was simulated with H2SO4, a combination of H2SO4 and HNO3, and HNO3 at two levels of moderate acidic loads close to the natural anthropogenic pollution levels of southern Scandinavia. The higher levels of acid applications resulted in acidification, as defined by humus chemistry. The concentrations of base cations decreased, while the concentrations of exchangeable H+, Al, and Fe increased. Humus pH decreased from 3.83 to 3.65. Basal respiration decreased with decreasing humus pH, and total microbial biomass, measured by substrate-induced respiration and total amount of phospholipid fatty acids (PLFA), decreased slightly. An altered PLFA pattern indicated a change in the microbial community structure at the higher levels of acid applications. In general, branched fatty acids, typical of gram-positive bacteria, increased in the acid plots. PLFA analysis performed on the bacterial community growing on agar plates also showed that the relative amount of PLFA specific for gram-positive bacteria increased due to the acidification. The changed bacterial community was adapted to the more acidic environment in the acid-treated plots, even though bacterial growth rates, estimated by thymidine and leucine incorporation, decreased with pH. Fungal activity (measured as acetate incorporation into ergosterol) was not affected. This result indicates that bacteria were more affected than fungi by the acidification. The capacity of the bacterial community to utilize 95 different carbon sources was variable and only showed weak correlations to pH. Differences in the toxicities of H2SO4 and HNO3 for the microbial community were not found.
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