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1.
Methane emissions from fen,bog and swamp peatlands in Quebec 总被引:8,自引:1,他引:7
A static chamber technique was used weekly from spring thaw to winter freezing to measure methane emissions from 10 sites representing subarctic fens and temperate swamps and bogs. Rates of < 200 mg CH4 m–2 d–1 were recorded in subarctic fens: within-site emissions were primarily controlled by the evolution of the peat thermal regime, though significant releases during spring thaw were recorded at some sites. Between subarctic fens, topography and water table elevation were important controls on methane emissions, with the general sequence: pool = horizontal fen> string. Emission rates from the 2 swamp sites were lower (< 20 mg CH4 m–2 d–1 ), except during the spring thaw and when the sites were saturated. The low water table ( < 80 cm depth) in abnormally dry years reduced emission rates; rates were also low from a swamp site which had been drained and cleared of vegetation for horticulture. Methane emission rates were also low (< 5 mg CH4 m–2 d–1) from 2 ombrotrophic bog sites. Laboratory measurements of rates of methane production under anaerobic conditions and methane consumption under aerobic conditions revealed that production rates were generally highest in the surface layers (0 to 2.5 cm depth); production was high in the fens and very low in the bogs. The swamp samples were able to produce methane under anaerobic conditions, but were also able to consume methane under aerobic conditions. Annual methane emission rates are estimated to be 1 to 10 g CH4 m–2 from the fens, 1 to 4 g CH4 m–2 from the swamps and <0.2 g CH4 m–2 from the bogs and drained swamp. 相似文献
2.
Many peatlands were affected by drainage in the past, and restoration of their water regime aims to bring back their original functions. The purpose of our study was to simulate re-wetting of soils of different types of drained peatlands (bogs and minerotrophic mires, located in the Sumava Mountains, Czech Republic) under laboratory conditions (incubation for 15 weeks) and to assess possible risks of peatland water regime restoration - especially nutrient leaching and the potentials for CO2 and CH4 production. After re-wetting of soils sampled from drained peatlands (simulated by anaerobic incubation) (i) phosphorus concentration (SRP) did not change in any soil, (ii) concentration of ammonium and dissolved organic nitrogen (DON) increased, but only in a drained fen, (iii) DOC increased significantly in the drained fen and degraded drained bog, (iv) CO2 production decreased, (v) CH4 production and the number of methanogens increased in all soils, and (vi) archaeal methanogenic community composition was also affected by re-wetting; it differed significantly between drained and pristine fens, whereas it was more similar between drained and pristine bogs. Overall, the soils from fens reacted more dynamically to re-wetting than the bogs, and therefore, some nutrients (especially nitrogen) and DOC leaching may be expected from drained fens after their water regime restoration. However, if compared to their state before restoration, ammonium and phosphorus leaching should not increase and leaching of nitrates and DON should even decrease after restoration, especially during the vegetation season. Further, CO2 production in soils of fens and bogs should decrease after their water regime restoration, whereas CH4 production in soils should increase. However, we cannot derive any clear conclusions about CH4 emissions from the ecosystems based on this study, as they depend strongly on environmental factors and on the actual activity of methanotrophs in situ. 相似文献
3.
Winter fluxes of methane from Minnesota peatlands 总被引:2,自引:2,他引:0
Nancy B. Dise 《Biogeochemistry》1992,17(2):71-83
Winter fluxes of methane were investigated in northern Minnesota during 1988–89 and 1989–90. Two bogs and a fen emitted methane throughout the snow-covered season (November through March). Fluxes decreased to a low level of 3–16 mg CH4 m–2 d–1 in late March, reflecting decreasing peat temperatures and (in 1989–90) increasing depth of frost in the peat. Winter fluxes calculated by integration for an open poor fen, an open bog, a forested bog hollow, and a hummock site in the forested bog averaged 49, 12, 13, and 5 mg m–2 d–1, respectively, in 1989–1990 (the year most measurements were made). These comprised 11%, 4%, 15%, and 21% of total annual flux. 相似文献
4.
Phosphorus retention and movement across an ombrotrophic-minerotrophic peatland gradient 总被引:8,自引:0,他引:8
An understanding of the mechanisms controlling nutrient availability and retention in and across ecosystems allows for a greater understanding of the role of nutrients in maintaining ecosystem structure and function. To examine the underlying mechanisms of phosphorus (P) cycling in northern peatlands, we compared the retention and movement of P across a natural hydrologic/pH gradient in nine peatlands by applying as a light rain an in situ tracer amount of 32PO4
–3 to track changes in P pools (vegetation, soil, microbial) over 30 days. The 31P concentrations of available P, microbial P, and the root P at 10–20 cm did not differ across the gradient, although total soil P and aboveground vegetation P content (g m–2) increased from bog to rich fen. Total retention of 32P in the first 24 hours of application was greatest in the bogs and intermediate fens (90–100%) and was very low (20–50%) in the rich fens. Retention of P in the different pools was dependent on the type of peatland and changed with time. In the first 24 hours in the bogs and intermediate fens, the microbial pool contained the largest amount of 32P, but by the seventh day, the aboveground vegetation contained the largest amount. In the rich fen, the recovered 32P was almost equally divided between the aboveground vegetation and the litter layer with very little in other pools. Therefore, although bogs and intermediate fens have a small total P pool, they have similar P availability to rich fens because of rapid cycling and efficient retention of P. 相似文献
5.
Change in fluxes of carbon dioxide,methane and nitrous oxide due to forest drainage of mire sites of different trophy 总被引:6,自引:0,他引:6
Northern peatlands accumulate atmospheric CO2 thus counteracting climate warming. However, CH4 which is more efficient as a greenhouse gas than CO2, is produced in the anaerobic decomposition processes in peat. When peatlands are taken for forestry their water table is lowered by ditching. We studied long-term effects of lowered water table on the development of vegetation and the annual emissions of CO2, CH4 and N2O in an ombrotrophic bog and in a minerotrophic fen in Finland. Reclamation of the peat sites for forestry had changed the composition and coverage of the field and ground layer species, and increased highly the growth of tree stand at the drained fen. In general, drainage increased the annual CO2 emissions but the emissions were also affected by the natural fluctuations of water table. In contrast to CO2, drainage had decreased the emissions of CH4, the drained fen even consumed atmospheric CH4. CO2 and CH4 emissions were higher in the virgin fen than in the virgin bog. There were no N2O emissions from neither type of virgin sites. Drainage had, however, highly increased the N2O emissions from the fen. The results suggest that post-drainage changes in gas fluxes depend on the trophy of the original mires. 相似文献
6.
Methane-oxidizing bacteria (MOB) are the only biological sinks for methane (CH4). Drainage of peatlands is known to decrease overall CH4 emission, but the effect on MOB is unknown. The objective of this work was to characterize the MOB community and activity
in two ecohydrologically different pristine peatland ecosystems, a fen and a bog, and their counterparts that were drained
in 1961. Oligotrophic fens are groundwater-fed peatlands, but ombrotrophic bogs receive additional water and nutrients only
from rainwater. The sites were sampled in August 2003 down to 10 cm below the water table (WT), and cores were divided into
10-cm subsamples. CH4 oxidation was measured by gas chromatography (GC) to characterize MOB activity. The MOB community structure was characterized
by polymerase chain reaction–denaturing gradient gel electrophoresis (DGGE) and sequencing methods using partial pmoA and mmoX genes. The highest CH4 oxidation rates were measured from the subsamples 20–30 and 30–40 cm above WT at the pristine oligotrophic fen (12.7 and
10.5 μmol CH4 dm−3 h−1, respectively), but the rates decreased to almost zero in the vicinity of WT. In the pristine ombrotrophic bog, the highest
oxidation rate at 0–10 cm was lower than in the fen (8.10 μmol CH4 dm−3 h−1), but in contrast to the fen, oxidation rates of 4.5 μmol CH4 dm−3 h−1 were observed at WT and 10 cm below WT. Drainage reduced the CH4 oxidation rates to maximum values of 1.67 and 5.77 μmol CH4 dm−3 h−1 at 30–40 and 20–30 cm of the fen and bog site, respectively. From the total of 13 pmoA-derived DGGE bands found in the study, 11, 3, 6, and 2 were observed in the pristine fen and bog and their drained counterparts,
respectively. According to the nonmetric multidimensional scaling of the DGGE banding pattern, the MOB community of the pristine
fen differed from the other sites. The majority of partial pmoA sequences belonged to type I MOB, whereas the partial mmoX bands that were observed only in the bog sites formed a distinct group relating more to type II MOB. This study indicates
that fen and bog ecosystems differ in MOB activity and community structure, and both these factors are affected by drainage. 相似文献
7.
Marianna Deppe Klaus-H. Knorr Diane M. McKnight Christian Blodau 《Biogeochemistry》2010,100(1-3):89-103
Atmospheric CO2 and CH4 exchange in peatlands is controlled by water table levels and soil moisture, but impacts of short periods of dryness and rainfall are poorly known. We conducted drying-rewetting experiments with mesocosms from an ombrotrophic northern bog and an alpine, minerotrophic fen. Efflux of CO2 and CH4 was measured using static chambers and turnover and diffusion rates were calculated from depth profiles of gas concentrations. Due to a much lower macroporosity in the fen compared to the bog peat, water table fluctuated more strongly when irrigation was stopped and resumed, about 11 cm in the fen and 5 cm in the bog peat. Small changes in air filled porosity caused CO2 and CH4 concentrations in the fen peat to be insensitive to changes in water table position. CO2 emission was by a factor of 5 higher in the fen than in the bog mesocosms and changed little with water table position in both peats. This was probably caused by the importance of the uppermost, permanently unsaturated zone for auto- and heterotrophic CO2 production, and a decoupling of air filled porosity from water table position. CH4 emission was <0.4 mmol m?2 day?1 in the bog peat, and up to >12.6 mmol m?2 day?1 in the fen peat, where it was lowered by water table fluctuations. CH4 production was limited to the saturated zone in the bog peat but proceeded in the capillary fringe of the fen peat. Water table drawdown partly led to inhibition of methanogenesis in the newly unsaturated zone, but CH4 production appeared to continue after irrigation without time-lag. The identified effects of irrigation on soil moisture and respiration highlight the importance of peat physical properties for respiratory dynamics; but the atmospheric carbon exchange was fairly insensitive to the small-scale fluctuations induced. 相似文献
8.
Functional-Structural Analysis of Nitrogen-Cycle Bacteria in a Hypersaline Mat from the Omani Desert
Anaerobic microbial activity in northern peat soils most often results in more carbon dioxide (CO 2 ) production than methane (CH4) production. This study examined why methanogenic conditions (i.e., equal molar amounts of CH4 production and CO2 production) prevail so infrequently. We used peat soils from two ombrotrophic bogs and from two rheotrophic fens. The former two represented a relatively dry bog hummock and a wet bog hollow, and the latter two represented a forested fen and a sedge-dominated fen. We quantified gas production rates in soil samples incubated in vitro with and without added metabolic substrates (glucose, ethanol, H2/CO2). None of the peat soils exhibited methanogenic conditions when incubated in vitro for a short time (< 5 days) and without added substrates. Incubating some samples > 50 days without added substrates led to methanogenic conditions in only one of four experiments. The anaerobic CO2:CH4 production ratio ranged from 5:1 to 40:1 in peat soil without additions and was larger in samples from the dry bog hummock and forested fen than the wet bog hollow and sedge fen. Adding ethanol or glucose separately to peat soils led to methanogenic conditions within 5 days after the addition by stimulating rates of CH4 production, suggesting CH4 production from both hydrogenotrophic and acetoclastic methanogenesis. Our results suggest that methanogenic conditions in peat soils rely on a constant supply of easily decomposable metabolic substrates. Sample handling and incubation procedures might obscure methanogenic conditions in peat soil incubated in vitro. 相似文献
9.
Drainage of peatlands for forestry starts a succession of ground vegetation in which mire species are gradually replaced by forest species. Some mire plant communities vanish quickly following the water-level drawdown; some may prevail longer in the moister patches of peatland. Drainage ditches, as a new kind of surface, introduce another component of spatial variation in drained peatlands. These variations were hypothesized to affect methane (CH4) fluxes from drained peatlands. Methane fluxes from different plant communities and unvegetated surfaces, including ditches, were measured at the drained part of Lakkasuo mire, Central Finland. The fluxes were found to be related to peatland site type, plant community, water-table position and soil temperature. At nutrient-rich fen sites fluxes between plant communities differed only a little: almost all plots acted as CH4 sinks (−0.9 to −0.4 mg CH4 m−2 d−1), with the exception of Eriophorum angustifolium Honck. communities, which emitted 0.9 g CH4 m−2 d−1. At nutrient-poor bog site the differences between plant communities were clearer. The highest emissions were measured from Eriophorum vaginatum L. communities (29.7 mg CH4 m−2 d−1), with a decreasing trend to Sphagna (10.0 mg CH4 m−2 d−1) and forest moss communities (2.6 mg CH4 m−2 d−1). CH4 emissions from different kinds of ditches were highly variable, and extremely high emissions (summertime averages 182–600 mg CH4 m−2 d−1) were measured from continuously water-covered ditches at the drained fen. Variability in the emissions was caused by differences in the origin and movement of water in the ditches, as well as differences in vegetation communities in the ditches. While drainage on average greatly decreases CH4 emissions from peatlands, a great spatial variability in fluxes is emerged. Emissions from ditches constantly covered with water, may in some cases have a great impact on the overall CH4 emissions from drained peatlands. 相似文献
10.
Carbon balance of rewetted and drained peat soils used for biomass production: a mesocosm study
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Sandhya Karki Lars Elsgaard Tanka P. Kandel Poul Erik Lærke 《Global Change Biology Bioenergy》2016,8(5):969-980
Rewetting of drained peatlands has been recommended to reduce CO2 emissions and to restore the carbon sink function of peatlands. Recently, the combination of rewetting and biomass production (paludiculture) has gained interest as a possible land use option in peatlands for obtaining such benefits of lower CO2 emissions without losing agricultural land. This study quantified the carbon balance (CO2, CH4 and harvested biomass C) of rewetted and drained peat soils under intensively managed reed canary grass (RCG) cultivation. Mesocosms were maintained at five different groundwater levels (GWLs), that is 0, 10, 20 cm below the soil surface, representing rewetted peat soils, and 30 and 40 cm below the soil surface, representing drained peat soils. Net ecosystem exchange (NEE) of CO2 and CH4 emissions was measured during the growing period of RCG (May to September) using transparent and opaque closed chamber methods. The average dry biomass yield was significantly lower from rewetted peat soils (12 Mg ha?1) than drained peat soils (15 Mg ha?1). Also, CO2 fluxes of gross primary production (GPP) and ecosystem respiration (ER) from rewetted peat soils were significantly lower than from drained peat soils, but net uptake of CO2 was higher from rewetted peat soils. Cumulative CH4 emissions were negligible (0.01 g CH4 m?2) from drained peat soils but were significantly higher (4.9 g CH4 m?2) from rewetted peat soils during measurement period (01 May–15 September 2013). The extrapolated annual C balance was 0.03 and 0.68 kg C m?2 from rewetted and drained peat soils, respectively, indicating that rewetting and paludiculture can reduce the loss of carbon from peatlands. 相似文献
11.
12.
Pristine peatlands are a significant source of atmospheric methane (CH4). Large spatio–temporal variation has been observed in flux rates within and between peatlands. Variation is commonly associated
with water level, vegetation structure, soil chemistry and climatic variability. We measured spatial and temporal variation
in CH4 fluxes in a blanket bog during the period 2003–2005. The surface of the bog was composed of different vegetation communities
(hummocks, lawns and hollows) along a water level gradient. CH4 fluxes were measured in each community using a chamber method. Regression modelling was used to relate the fluxes with environmental
variables and to integrate fluxes over the study period. Water level was the strongest controller of spatial variation; the
average flux rate was lowest in hummocks and highest in hollows, ranging from 3 to 53 mg CH4 m−2 day−1. In vegetation communities with a permanently high water level, the amount and species composition of vegetation was also
a good indicator of flux rate. We observed a clear seasonal variation in flux that was chiefly controlled by temperature.
The annual average flux (6.2 g CH4 m−2 year−1) was similar to previous estimates from blanket bogs and continental raised bogs. No interannual variation was observed. 相似文献
13.
Jüri-Ott Salm Martin Maddison Sille Tammik Kaido Soosaar Jaak Truu Ülo Mander 《Hydrobiologia》2012,692(1):41-55
The aim of this study is to estimate emissions of greenhouse gases CO2, CH4 and N2O, and the effects of drainage and peat extraction on these processes, in Estonian transitional fens and ombrotrophic bogs. Closed-chamber-based sampling lasted from January to December 2009 in nine peatlands in Estonia, covering areas with different land-use practices: natural (four study sites), drained (six sites), abandoned peat mining (five sites) and active peat mining areas (five sites). Median values of soil CO2 efflux were 1,509, 1,921, 2,845 and 1,741 kg CO2-C ha?1 year?1 from natural, drained, abandoned and active mining areas, respectively. Emission of CH4-C (median values) was 85.2, 23.7, 0.07 and 0.12 kg ha?1 year?1, and N2O-N ?0.05, ?0.01, 0.18 and 0.19 kg ha?1 year?1, respectively. There were significantly higher emissions of CO2 and N2O from abandoned and active peat mining areas, whereas CH4 emissions were significantly higher in natural and drained areas. Significant Spearman rank correlation was found between soil temperature and CO2 flux at all sites, and CH4 flux with high water level at natural and drained areas. Significant increase in CH4 flux was detected for groundwater levels above 30 cm. 相似文献
14.
Emission of N2O, N2, CH4, and CO2 from constructed wetlands for wastewater treatment and from riparian buffer zones 总被引:3,自引:1,他引:2
We measured nitrous oxide (N2O), dinitrogen (N2), methane (CH4), and carbon dioxide (CO2) fluxes in horizontal and vertical flow constructed wetlands (CW) and in a riparian alder stand in southern Estonia using the closed chamber method in the period from October 2001 to November 2003. The replicates’ average values of N2O, N2, CH4 and CO2 fluxes from the riparian gray alder stand varied from −0.4 to 58 μg N2O-N m−2 h−1, 0.02–17.4 mg N2-N m−2 h−1, 0.1–265 μg CH4-C m−2 h−1 and 55–61 mg CO2-C m−2 h−1, respectively. In horizontal subsurface flow (HSSF) beds of CWs, the average N2 emission varied from 0.17 to 130 and from 0.33 to 119 mg N2-N m−2 h−1 in the vertical subsurface flow (VSSF) beds. The average N2O-N emission from the microsites above the inflow pipes of the HSSF CWs was 6.4–31 μg N2O-N m−2 h−1, whereas the outflow microsites emitted 2.4–8 μg N2O-N m−2 h−1. In VSSF beds, the same value was 35.6–44.7 μg N2O-N m−2 h−1. The average CH4 emission from the inflow and outflow microsites in the HSSF CWs differed significantly, ranging from 640 to 9715 and from 30 to 770 μg CH4-C m−2 h−1, respectively. The average CO2 emission was somewhat higher in VSSF beds (140–291 mg CO2-C m−2 h−1) and at the inflow microsites of HSSF beds (61–140 mg CO2-C m−2 h−1). The global warming potential (GWP) from N2O and CH4 was comparatively high in both types of CWs (4.8 ± 9.8 and 6.8 ± 16.2 t CO2 eq ha−1 a−1 in the HSSF CW 6.5 ± 13.0 and 5.3 ± 24.7 t CO2 eq ha−1 a−1 in the hybrid CW, respectively). The GWP of the riparian alder forest from both N2O and CH4 was relatively low (0.4 ± 1.0 and 0.1 ± 0.30 t CO2 eq ha−1 a−1, respectively), whereas the CO2-C flux was remarkable (3.5 ± 3.7 t ha−1 a−1). The global influence of CWs is not significant. Even if all global domestic wastewater were treated by wetlands, their share of the trace gas emission budget would be less than 1%. 相似文献
15.
Exchange of CO2, CH4 and N2O between the atmosphere and two northern boreal ponds with catchments dominated by peatlands or forests 总被引:1,自引:0,他引:1
Huttunen Jari T. Väisänen Tero S. Heikkinen Mirja Hellsten Seppo Nykänen Hannu Nenonen Olli Martikainen Pertti J. 《Plant and Soil》2002,242(1):137-146
Concentrations of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) in the water column and their exchange at the water/air interface were studied during the open water period in two freshwater ponds with different catchment characteristics in the northern boreal zone in Finland; either peatlands or coniferous upland forests dominated the catchment of the ponds. Both ponds were supersaturated with dissolved CO2 and CH4 with respect to the equilibrium with the atmosphere, but were close to the equilibrium with N2O. The mean CO2 efflux from the pond was higher in the peatland-dominated catchment (22 mg m–2 h–1) than in the forested catchment (0.7 mg m–2 h–1), whereas the mean CH4 emissions were similar (7.6 and 3.5 mg m–2 d–1, respectively). The fluxes of N2O were generally negligible. The higher CO2 concentrations and efflux in the pond with the peatland-dominated catchment were attributed to a greater input of allochthonous carbon to that pond from its catchment due to its higher water colour and higher total organic carbon (TOC) concentration. The water pH, which also differed between the ponds, could additionally affect the CO2 dynamics. Since the catchment characteristics can regulate aquatic carbon cycles, catchment-scale studies are needed to attain a deeper understanding of the aquatic greenhouse gas dynamics. 相似文献
16.
Fluxes of nitrous oxide and methane from drained peatlands following forest clear-felling in southern Finland 总被引:3,自引:1,他引:2
Jari T. Huttunen Hannu Nykänen Pertti J. Martikainen Mika Nieminen 《Plant and Soil》2003,255(2):457-462
Drainage of waterlogged sites has been part of the normal forestry practice in Fennoscandia, the Baltic countries, the British Isles and in some parts of Russia since the early 20th century, and currently, about 15 million hectares of peatlands and other wetlands have been drained for forestry purposes. The rate of forest clear-felling on drained peatlands will undergo a rapid increase in the near future, when a large number of these forests approach their regeneration age. A small-scale pilot survey was performed at two nutrient-rich and old peatland drainage areas in southern Finland to study if forest clear-felling has significant impacts on the exchange of nitrous oxide (N2O) and methane (CH4) between soil and atmosphere. The average N2O emissions from the two drainage areas during three growing seasons following clear-felling were 945 and 246 g m–2 d–1. The corresponding CH4 fluxes were –0.07 and –0.52 mg m–2 d–1. Clear-felling had impacts on the environmental factors known to affect the N2O and CH4 fluxes of peatlands, i.e. clear-felling raised the water table level and increased the peat temperature. However, no substantial changes in the fluxes of CH4 following clear-felling were observed. The results concerning N2O indicated a potential for increased emissions following clear-felling of drained peatland forests, but further studies are needed for a critical evaluation of the impacts of clear-felling on the fluxes of CH4 and N2O. 相似文献
17.
Helen Karu Margus Pensa Eva-Ingrid Rõõm Angelika Portsmuth Triin Triisberg 《Wetlands Ecology and Management》2014,22(4):399-417
Bog ecosystems are sensitive to anthropogenic disturbance, including drainage and air pollution. Carbon (C) balance measurements to determine the effect of disturbance on bog functioning are laborious; therefore reliable proxies for C fluxes that could facilitate upscaling from single studies to a larger scale would be valuable. We measured peat CO2 emissions (R s), CH4 efflux and vegetation characteristics in four bog areas that formed a gradient from pristine to severely disturbed peatlands, affected by drainage, peat mining, alkaline air pollution and underground oil-shale mining. We expected that sites experiencing higher human impact (i.e., the vegetation was more distinct from that of a natural bog) would have higher R s and lower CH4 emissions, but differences in peat C emissions between the most disturbed and pristine sites were not significant. Growing period median R s ranged from 0.5 to 2.2 g C m?2 day?1 for our plots; methane emissions, measured from July to December were an order of magnitude lower, ranging from ?5.9 to 126.7 mg C m?2 day?1. R s and CH4 emissions were primarily determined by water table depth, as was tree stand productivity. Therefore, stand structural parameters could potentially be good indicators of soil C emissions from poorly drained forested bogs. 相似文献
18.
The active methanotroph community was investigated in two contrasting North American peatlands, a nutrient-rich sedge fen
and nutrient-poor Sphagnum bog using in vitro incubations and 13C-DNA stable-isotope probing (SIP) to measure methane (CH4) oxidation rates and label active microbes followed by fingerprinting and sequencing of bacterial and archaeal 16S rDNA and
methane monooxygenase (pmoA and mmoX) genes. Rates of CH4 oxidation were slightly, but significantly, faster in the bog and methanotrophs belonged to the class Alphaproteobacteria
and were similar to other methanotrophs of the genera Methylocystis, Methylosinus, and Methylocapsa or Methylocella detected in, or isolated from, European bogs. The fen had a greater phylogenetic diversity of organisms that had assimilated
13C, including methanotrophs from both the Alpha- and Gammaproteobacteria classes and other potentially non-methanotrophic organisms
that were similar to bacteria detected in a UK and Finnish fen. Based on similarities between bacteria in our sites and those
in Europe, including Russia, we conclude that site physicochemical characteristics rather than biogeography controlled the
phylogenetic diversity of active methanotrophs and that differences in phylogenetic diversity between the bog and fen did
not relate to measured CH4 oxidation rates. A single crenarchaeon in the bog site appeared to be assimilating 13C in 16S rDNA; however, its phylogenetic similarity to other CO2-utilizing archaea probably indicates that this organism is not directly involved in CH4 oxidation in peat. 相似文献
19.
Climate change effects on carbon and nitrogen mineralization in peatlands through changes in soil quality 总被引:8,自引:0,他引:8
Jason K. Keller Jeffrey R. White† Scott D. Bridgham‡ John Pastor§ 《Global Change Biology》2004,10(7):1053-1064
Climate change will directly affect carbon and nitrogen mineralization through changes in temperature and soil moisture, but it may also indirectly affect mineralization rates through changes in soil quality. We used an experimental mesocosm system to examine the effects of 6‐year manipulations of infrared loading (warming) and water‐table level on the potential anaerobic nitrogen and carbon (as carbon dioxide (CO2) and methane (CH4) production) mineralization potentials of bog and fen peat over 11 weeks under uniform anaerobic conditions. To investigate the response of the dominant methanogenic pathways, we also analyzed the stable isotope composition of CH4 produced in the samples. Bog peat from the highest water‐table treatment produced more CO2 than bog peat from drier mesocosms. Fen peat from the highest water‐table treatment produced the most CH4. Cumulative nitrogen mineralization was lowest in bog peat from the warmest treatment and lowest in the fen peat from the highest water‐table treatment. As all samples were incubated under constant conditions, observed differences in mineralization patterns reflect changes in soil quality in response to climate treatments. The largest treatment effects on carbon mineralization as CO2 occurred early in the incubations and were ameliorated over time, suggesting that the climate treatments changed the size and/or quality of a small labile carbon pool. CH4 from the fen peat appeared to be predominately from the acetoclastic pathway, while in the bog peat a strong CH4 oxidation signal was present despite the anaerobic conditions of our incubations. There was no evidence that changes in soil quality have lead to differences in the dominant methanogenic pathways in these systems. Overall, our results suggest that even relatively short‐term changes in climate can alter the quality of peat in bogs and fens, which could alter the response of peatland carbon and nitrogen mineralization to future climate change. 相似文献
20.
Microbial population dynamics in an extreme environment: controlling factors in talus soils at 3750 m in the Colorado Rocky Mountains 总被引:3,自引:3,他引:0
Variation of CH4 emissions over a three-year period was studied in a reed-dominated (Phragmites australis) littoral transect of a boreal lake undergoing shoreline displacement due to postglacial rebound. The seasonal variation in plant-mediated CH4 emissions during open-water periods was significantly correlated with sediment temperature. The highest plant-mediated emission rates (up to 2050 mg CH4 m–2 d–1) were found in the outermost reed zone, where culms of the previous growing seasons had accumulated and free-floating plants grew on the decomposing culms. In reed zones closer to the shoreline as well as in mixed stands of reed and cattail, the maximum daily rates were usually > 500 mg CH4 m–2 d–1. The total plant-mediated CH4 emission during the open-water period was significantly correlated with the seasonal maximum of green shoot biomass. This relationship was strongest in the continuously flooded (water depth > 25 cm) outermost zones. In this area, emissions through ebullition were of greatest importance and could exceed plant-mediated emissions. In general, total emissions of the open-water periods varied from ca. 20 to 50 g CH4 m–2 a–1, but in the outermost reed zone, the plant-mediated emissions could be as high as 123 g CH4 m–2 a–1; ebullition emissions from this zone reached > 100 g CH4 m–2 a–1. The proportion of CH4 released in winter was usually < 10% of annual emissions. Emissions of CH4 were higher in this flooded transgression shore the than those measured in boreal peatlands, but the role of ancient carbon stores as a substrate supply compared with recent anthropogenic eutrophication is unknown. 相似文献