Mesotrophic Fen Research Articles

Exploring the Holocene rise, disturbance and decline of pine forests in the river valleys of northeastern Belgium using pollen and botanical macroremains

The Holocene evolution of vegetation and environment in the Kleine Nete valley in the coversand region of northeastern Belgium is studied through sedimentological, palynological and macrobotanical analysis of a radiocarbon dated peat sequence. Peat formation started at the beginning of the Holocene in mesotrophic fen conditions. After a period of fast peat growth, the accumulation slowed down and the peat surface became dry in the Middle Holocene.The palynological results are compared with other pollen data from the region, in order to establish a regional pollen biozonation for the Early and Middle Holocene in the Nete Basin. This shows that pine has long been a characteristic element in the Nete Basin. Pine forest expanded immediately after the 11.4 cold event, which is earlier than in the western Scheldt Basin. Pine and birch grew along the valley, possibly also within the peatland. Peaks of microcharcoal, herbs and/or coarse sediment in the peat reflect temporary local forest disturbances in the Early Holocene. Some may reflect small-scale controlled fires induced by hunter-gatherers, although a natural cause seems much more plausible given the dominance of fire-associated pines and increased drought. Pine remained important throughout the Early Holocene. This long-lasting predominance of pine in the Nete Basin, compared to elsewhere in the Scheldt Basin, is likely related to the poor sandy subsoil in the region, which hinders more nutrient-demanding broadleaf trees to overtake.

Lateglacial to Middle Holocene landscape development in a small-sized river valley near Antwerp (Belgium)

At the transition between the Scheldt valley and the Campine microcuesta near Antwerp, two separate organic deposits are present in the subsoil. Sedimentological, macrobotanical and palynological analyses from two cores are used to reconstruct the evolutions of the local depositional and ecological environment, as well as the regional vegetation. An age-depth model based on radiocarbon dates allows to frame those evolutions chronologically. During the Weichselian lateglacial, a mesotrophic lake was filled with peat during GI-1. The sand input indicates continued aeolian activity, also during forested phases. This peat was covered by wind deposits during GS-1. From the start of the Holocene onwards, a river channel in the Opstal Valley started to fill with peat in a mesotrophic fen. Pollen records show a temporary opening of the regional forest, that can be linked to the 11.4 ka event. The peat dried out around 11,000 cal BP and wetter conditions returned by the beginning of the Middle Holocene, with the development of an alder/birch carr. Unlike the Scheldt valley, the Opstal valley was not under tidal influence in the Middle Holocene. After ca. 6000 cal BP, the valley was part of the coastal peatlands that evolved from mesotrophic fen into oligotrophic bog.

Is 15% restoration sufficient to safeguard the habitats of boreal red-listed mire plant species?

We used habitat suitability modeling to investigate whether the 15% ecosystem restoration target set in the previous Convention of Biological Diversity (CBD) and EU Biodiversity strategy targets, is sufficient to safeguard red-listed mire plant species. We assessed six theoretical restoration scenarios for drained peatland landscapes by altering the proportion of drained and undrained peatland area in 25-ha grid cells. The proportions represented steps when 15%, 30%, 45%, 60%, 75% and 100% of the drained peatland is restored. We modelled the habitat suitability for 48 red-listed plant species in the aapa mire region in boreal Finland. Model outcomes were assessed at the level of five species groups: calcareous species, rich fen species, decaying wood species, mesotrophic fen species, and spruce swamp species. The predicted distribution increased for 34 (71%) of the 48 red-listed plant species when 15% of drained peatland area was predicted to be restored. At the same time the potentially occupied area of species increased by 9%. In the scenario where all peatlands were restored, the predicted distribution of 43 (90%) of species increased, and on average the distribution of species quadrupled. According to our predictions, meeting the 15% ecosystem restoration target, set in the previous CBD and EU Biodiversity strategy targets would be beneficial for most of the boreal red-listed mire plant species, but a larger restoration area would expand their distribution considerably more. Our study shows that a landscape level approach is important to assess thresholds for the potential biodiversity benefits arising from peatland restoration. The models can also be used to select suitable areas for restoration.

МОДЕЛИРОВАНИЕ СЕЗОННОГО ХОДА УГЛЕРОДНОГО ОБМЕНА В БОЛОТНЫХ ЭКОСИСТЕМАХ

The paper summarizes the results of expeditionary studies to study biological productivity, carbon dioxide fluxes in the bog ecosystems of the Central Taiga of Western Siberia. The paper summarizes the results of expeditionary studies to study biological productivity, carbon dioxide fluxes in the bog ecosystems of the Central Taiga of Western Siberia. Measurements of carbon dioxide fluxes were carried out from July 7 to July 14, 2019 at six observation sites located on the territory of typical wetland ecosystems of eutrophic, mesotrophic and oligotrophic types, taking into account the diversity of microlandscapes. Automatic measurements of the CO2 fluxes were carried out using the Licor LI-8100A soil respiration system. To extend the obtained observation data to other periods and to calculate the annual carbon balance of the ecosystem, a net ecosystem exchange (NEE) model was proposed, and the net fluxes of greenhouse gases for the growing season were calculated. The model uses air temperature and incoming photosynthetically active radiation as explanatory factors for gross primary production and ecosystem respiration. The model was calibrated in accordance with field measurements of carbon dioxide fluxes. For each observation site, six parameters were determined: two parameters for the photosynthesis model, two parameters for the respiration model and two for the biomass growth model. As a result of calculations for the period from May to October 2019, time series of fluxes of carbon dioxide absorption by vegetation during photosynthesis, CO2 release during ecosystem respiration, and the resulting flux – net ecosystem exchange were obtained. In the annual course, an increase in the intensity of photosynthesis during the daytime is associated with both the annual course of solar radiation and the accumulation of plant biomass. It was found that the net ecosystem exchange varies more strongly than its components. The NEE for ecosystems without vegetation is always positive. NEE is negative for the hollow and the open transit mesotrophic fen on any day of the growing season. Other ecosystems show both positive and negative daily mean fluxes. Wetland ecosystems with large biomass storages have significant fluxes (more than 1500 g CO2 / m2 ) associated with photosynthesis, but they also have a large expenditure component of carbon exchange (750–2200 g / m2 ). As a result, it was found that the greatest total absorption of carbon dioxide is observed in the mesotrophic sedge- menyanthes fen (1062 g / m2 ) and in the low ryam, taking into account the tree layer (603 g / m2 ). Other wetlands accumulate 244–466 g / m2 from the atmosphere during the growing season.

Application of an open-path eddy covariance methane flux measurement system to a larch forest in eastern Siberia

Canopy-Scale methane (CH4) flux measurement over a larch forest in eastern Siberia was conducted by eddy covariance method using an open-path CH4 gas analyzer. Though the uncorrected flux showed strong CH4 uptake in the daytime, this changed to CH4 emission after density and spectroscopic effects were corrected. Random flux errors calculated from cross-covariance functions suggested that CH4 flux was nearly the same as the upper boundary of the limit of flux detection at the 95th percentile, being barely resolved by the measurement system; and that most of the daytime CH4 flux remained positive even after uncertainties due to random flux errors were taken into consideration. CH4 flux showed clear diurnal variation, representing emission in the daytime and near-zero in the nighttime, irrespective of wind direction. The daytime CH4 flux was dependent on both air temperature and volumetric soil water content. The CH4 flux from May 29, to June 12, was calculated as net emissions of 4.9–13.8 nmol m−2 s−1 in daily average, ranging between the forest floor and a mesotrophic fen near this site measured by static chambers in a previous study.

Modelling the specific pathway of CH4 and CO2 formation using carbon isotope fractionation: an example for a boreal mesotrophic fen

ABSTRACTWe described mathematically the process of peat methanization in a boreal mesotrophic fen. Gaseous and dissolved CH4 and CO2 as well as their δ13C signatures were considered in the dynamic equations for incubation bottles. In accordance with the model, acetate, H2, and CO2 were produced during cellulose hydrolysis and acidogenesis. 13C/12C in CO2 was a key variable reflecting dynamic changes in the rates of cellulose hydrolysis and acidogenesis, acetoclastic and hydrogenotrophic methanogenesis. As CO2 is the substrate in hydrogenotrophic methanogenesis, δ13C–CO2 increased from the start till the dissolved hydrogen concentration became very low. Thereafter, the rate of acetoclastic methanogenesis with the significant current acetate concentration dominated over the rate of hydrogenotrophic methanogenesis leading to the decreasing δ13C–CO2 and the increasing δ13C–CH4. The model was validated by describing the system’s dynamics under strong and weak inhibition of acetoclastic and hydrogenotrophic methanogenesis by methyl fluoride, respectively. During peat methanization at the lowered temperature of 10 °C, the processes of hydrogenotrophic methanogenesis and homoacetogenesis competing for H2 may occur. However, based on dynamics of the carbon isotope signatures, especially on dynamics of δ13C–CO2, the model showed no significant contribution of homoacetogens in peat methanization.

Distinct Anaerobic Bacterial Consumers of Cellobiose-Derived Carbon in Boreal Fens with Different CO2/CH4 Production Ratios.

Peatlands are major sources of the greenhouse gas methane (CH4), yet in many peatlands, CO2 production from unresolved anaerobic processes exceeds CH4 production. Anaerobic degradation produces the precursors of CH4 production but also represents competing processes. We show that anaerobic degradation leading to high or low CH4 production involved distinct sets of bacteria. Well-known fermenters dominated in a peatland with high CH4 production, while novel and unconventional degraders could be identified in a site where CO2 production greatly exceeds CH4 production. Our results help identify and assign functions to uncharacterized bacteria that promote or inhibit CH4 production and reveal bacteria potentially producing the excess CO2 in acidic peat. This study contributes to understanding the microbiological basis for different levels of CH4 emission from peatlands.

Wetland restoration management under the aspect of climate change at a mesotrophic fen in Northern Germany

Wetland restoration management is an important tool for stakeholders and practitioners to mitigate climate change and preserve ecological functioning. Various approaches to modifying the water management of a catchment for restoration purposes exist and were performed in a preservation area in northwest Germany. To validate the effect of the re-wetting practice, a monitoring network of 46 wells was established and monthly readings were taken from 1997 onwards. A declining trend in water table depth was present at 39 wells and equaled on average a lowering of 20cm during the study period from 1997 to 2012. So far, half of the trend lines are above 40cm below ground, which is an indicator of an effective re-wetting practice, but they will decline below this threshold until 2032 according to linear regression analysis. The progress of water table depths might be accelerated by climate change. According to the meteorological forecast, air temperatures will rise and the annual precipitation pattern will change. Thus, the climatic water balance tends toward more negative values in the summer and positive values in the winter, favoring an earlier and more intense water table draw-down. Because root water extraction from shallow groundwater is limited to a certain depth, the forecast of water table depth development according to the recent trend depicts a worst-case scenario. Nevertheless, the results emphasize that restoration management should be validated and has to be adapted in certain ways when mitigating the impact of climate change.

Measuring the efficiency of fen restoration on carabid beetles and vascular plants: a case study from north‐eastern Germany

The aim of the study was to assess the effects of fen rewetting on carabid beetle and vascular plant assemblages within riverine fens along the river Peene in north‐eastern Germany. Drained (silage grassland), rewetted (restored formerly drained silage grassland), and near‐natural (fairly pristine) stands were compared. Eighty‐four beetle species (7,267 individuals) and 135 plant species were recorded. The richness of vascular plant species and the number of endangered species were highest on near‐natural fens. Fourteen years of rewetting did not increase plant species numbers compared with drained fens. For carabid beetles, however, species richness and the number of stenotopic species were highest on rewetted fens. Rewetting caused the replacement of generalist carabids by wetland specialists, but did not provide suitable habitat for specialist fen carabids or for plant species of oligo‐ or mesotrophic fen communities. Therefore, raising the water table on fens with nutrient‐rich, degraded peat was not sufficient for restoring species assemblages of intact fens, although water level was the most important environmental factor separating species assemblages. Our study illustrated that insects and plants may respond differentially to restoration, stressing the need to consider different taxa when assessing the efficiency of fen restoration. Furthermore, species assemblages of intact fens could not be restored within 14 years, highlighting the importance of conserving pristine habitat.

Four decades of vegetation development in a percolation mire complex following intensive drainage and abandonment

Background: Many minerotrophic fens in Central Europe have undergone similar sequences of land-use transformation. Drained and used as meadows or pastures for decades in the twentieth century, they were abandoned in the 1990s due to changes in agricultural economics. This sequence of land-use change has a severe impact on vegetation and is likely to initiate secondary succession and is possibly leading to an impoverishment in species diversity and to taxonomic homogenisation.Aims: We assess the impact of agricultural use and subsequent abandonment on vegetation composition in a percolation fen in north Germany and characterise successional changes and changes in abiotic site conditions.Methods: In 2010, we resampled 77 plots of a phytosociological survey from 1967–1970 in a lowland percolation mire complex in the lower Recknitz valley, north-east Germany. These included three characteristic vegetation types of percolation fens. To investigate and quantify vegetation changes we used dissimilarity measures, diversity metrics and ecological species indicator values.Results: Overall species richness declined only slightly while there was a more pronounced decrease in species richness at the plot level in all recorded vegetation types, resulting in increased beta diversity. Generalist and nitrophilous species increased in abundance, indicating ongoing succession.Conclusions: Drainage for agricultural use and subsequent abandonment has long-lasting effects. Altered hydrological and nutrient status of the fen soil has initiated secondary succession. There is indication of an extinction debt that in the future may lead to an impoverishment of species diversity in the area. Conservation of open mesotrophic fen species may thus only be achieved if moderate use is continued and hydrologic conservation measures are applied on wide contiguous areas.

Effect of mowing on productivity in the endangered Aquatic Warbler Acrocephalus paludicola

SummaryThe Aquatic Warbler Acrocephalus paludicola is a globally threatened habitat specialist that breeds in open fens in Central and Eastern Europe. Because bush and reed encroachment threaten many suitable breeding areas, habitat management is necessary to maintain the open wetlands that Aquatic Warblers require for nesting. The effectiveness of mowing as habitat management has so far only been assessed by counting the number of singing males. To assess whether mowing also affected vital reproduction parameters, we analysed Aquatic Warbler productivity in the Biebrza National Park, Poland, on plots in four different successional stages after mowing. Our study showed that productivity was lowest in the first year after mowing, but increased to the highest levels in the second year after mowing. The productivity differences between areas at different stages after mowing resulted from differences in nest density, since we found little evidence for an effect of mowing on nest survival or the number of fledglings produced per successful nest. Nest survival was highly variable between years and varied mostly with nest age and nest initiation date. The density of singing males was positively correlated with both the nest density and the number of fledglings produced in an area, suggesting that this simple indicator could be used to rank the quality of Aquatic Warbler habitats. We recommend that in mesotrophic fen mires, such as the Biebrza valley, mowing as habitat management is applied less frequently than every second year.

Estimating evolution of δ13CH4 during methanogenesis in the boreal peatland ecosystems based on stoichiometric chemical reactions, microbial dynamics and stable carbon isotope fractionation

A change in natural isotopic composition of products may be used to reveal metabolic pathways of substrate transformation by microbial community (Vavilin, 2012). In this study, data of δ13CH4 obtained during methanization of organic material from three boreal peatland ecosystems, previously measured and evaluated by Galand et al. (2010), was used to describe mathematically a system dynamics of peat transformation. In the system of differential equations, both stoichiometric chemical reactions and an equation for the 13C isotope accumulation in products including isotope fractionation and microbial dynamics were considered. The model confirm that acetoclastic and hydrogenotrophic methanogenesis occurred with high methane production rates during cellulose methanization in the mesotrophic fen (MES) while hydrogenotrophic methanogenesis happened without intermediate acetate production during non-canonical cellulose methanization in the nutrient-poor peat (OLI – oligotrophic fen, OMB – ombrotrophic peat). This was in agreement with Galand et al. (2010). The model showed that a value of δ13CH4 depended on acetoclastic and hydrogenotrophic methanogenesis rates and on coefficients of stable carbon isotopes fractionation. A strong kinetic fractionation factor (1.064–1.087) was used for hydrogenotrophic methanogenesis. The produced volumes of CH4 and CO2 were about 1:1 (MES) and 1:2 (OLI, OMB) which was in accordance with stoichiometric chemical reactions. Inhibition of methanogenesis by methyl fluoride (CH3F) was described in the model assuming exponential decrease of methane production rate in time which was about 3.6 times higher for acetoclastic methanogenesis when compared to hydrogenotrophic methanogenesis. It was confirmed that CH3F resulted in a strong decrease of δ13CH4 in MES only.

Home Range and Habitat use by Aquatic WarblersAcrocephalus paludicolaon their Wintering Grounds in Northwestern Senegal

The Aquatic Warbler Acrocephalus paludicola was once a common breeding bird in mesotrophic fen mires all over Central and Western Europe. In the last century large parts of its habitat have been destroyed by wetland drainage and agricultural intensification. Besides protecting the remaining breeding habitats, it is of great importance to preserve suitable migration stopover habitats and wintering grounds to avert the extinction of the species.We determined home-range size and the use of vegetation associations of Aquatic Warblers on the wintering grounds in a flooded plain north of the Djoudj National Park in Senegal. Individual birds (11) were caught in mist nets and equipped with radio transmitters. Locations were assessed by radiotelemetry and a compositional analysis was conducted to determine which vegetation types were preferred within home ranges.Similar to their behaviour on the breeding grounds, the Aquatic Warblers showed no territorial behaviour in their winter quarters. They used home ranges that averaged 4 ha in size, which they shared with conspecifics and other warblers. The home ranges overlapped 54% on average, with a maximum of 90% in an area used by four individuals. The vegetation structure of the wintering habitat is similar to breeding grounds and stopover sites of the species. Preferential vegetation had 80% to 100% cover and consisted of 60 to 90 cm high stands of Oryza longistaminata, Scirpus maritimus or Eleocharis mutata. Most birds stayed more often near the edge of open water, probably for foraging. A constant inundation seems essential, because Aquatic Warblers never occurred in desiccated parts of the study site.

Differential effects of ammonium and nitrate deposition on fen phanerogams and bryophytes

Question: High atmospheric nitrogen (N) deposition has been shown to affect productivity and species composition of terrestrial ecosystems. This study focused on the differential effects of the two inorganic N forms in atmospheric deposition (i.e. ammonium and nitrate). Methods and location: Nutrient addition experiments were carried out during 4 years in a mesotrophic fen in a low-deposition area in Ireland. In a factorial design, plots were fertilized with ammonium and/or nitrate, in two doses comparable with 35 and 70 kg N ha−1 y−1 and compared with an unfertilized control. Results: Vascular plant biomass as well as bryophyte biomass were not affected by N dose but showed significantly different responses to the N form. In the ammonium-fertilized plots, vascular plant biomass was higher and moss biomass was lower than the control, while nitrate additions had no effect. Vascular plant species density was high (16 species per 0.49 m2) and was not affected by any of the treatments; bryophyte species density was also high (seven species per 0.04 m2) but showed a significant decrease upon ammonium fertilization. Conclusion: The vulnerability of the mesotrophic vegetation to enhanced atmospheric N deposition depends strongly on the N form. If N would be mainly deposited as NOx, no detrimental effects on the vegetation will occur. If, however, the deposition is mainly in the form of NHy, the bryophyte vegetation will be seriously damaged, while the vascular plant vegetation will show an increased biomass production with possible shifts in dominance from Carex and herb species to grasses and shrubs.

Stable carbon isotope fractionation during methanogenesis in three boreal peatland ecosystems

Abstract. The degradation of organic matter to CH4 and CO2 was investigated in three different boreal peatland systems in Finland, a mesotrophic fen (MES), an oligotrophic fen (OLI), and an ombrotrophic peat (OMB). MES had similar production rates of CO2 and CH4, but the two nutrient-poor peatlands (OLI and OMB) produced in general more CO2 than CH4. δ13C analysis of CH4 and CO2 in the presence and absence methyl fluoride (CH3F), an inhibitor of acetoclastic methanogenesis, showed that CH4 was predominantly produced by hydrogenotrophic methanogenesis and that acetoclastic methanogenesis only played an important role in MES. These results, together with our observations concerning the collective inhibition of CH4 and CO2 production rates by CH3F, indicate that organic matter was degraded through different paths in the mesotrophic and the nutrient-poor peatlands. In the mesotrophic fen, the major process is canonical fermentation followed by acetoclastic and hydrogenotrophic methanogenesis, while in the nutrient-poor peat, organic matter was apparently degraded to a large extent by a different path which finally involved hydrogenotrophic methanogenesis. Our data suggest that degradation of organic substances in the oligotrophic environments was incomplete and involved the use of organic compounds as oxidants.

Long‐term drainage for forestry inhibits extracellular phenol oxidase activity in Finnish boreal mire peat

Drainage for forestry has been amongst the most extensive of land management practices applied to northern latitude peatlands, particularly in northern Europe. Extracellular phenol oxidases play an important role in the carbon cycle of soils. This study investigated the effects of long‐term (45 years) drainage for forestry upon surface peat extracellular phenol oxidase activity, soluble phenolic concentrations and pH at ombrotrophic bog, oligotrophic fen and mesotrophic fen sites at a Finnish mire complex. Phenol oxidase activity was reduced by drainage at all three sites. Phenol oxidase activity was positively correlated with peat pH across all sites irrespective of drainage treatment, suggesting that pH is a major factor influencing peat phenol oxidase activity at the mire complex. Peat pH became more acidic with drainage at the fen sites, and it is likely that this contributed to the suppression of peat phenol oxidase activity. The reduction of peat phenol oxidase activity with drainage was accompanied by increased concentrations of water‐soluble phenolics at all three sites, and the potential contribution of this to changes in peat carbon stocks following drainage is discussed.

Response of fungal and actinobacterial communities to water-level drawdown in boreal peatland sites

We used PCR-DGGE fingerprinting and direct sequencing to analyse the response of fungal and actinobacterial communities to changing hydrological conditions at 3 different sites in a boreal peatland complex in Finland. The experimental design involved a short-term (3 years; STD) and a long-term (43 years; LTD) water-level drawdown. Correspondence analyses of DGGE bands revealed differences in the communities between natural sites representing the nutrient-rich mesotrophic fen, the nutrient-poorer oligotrophic fen, and the nutrient-poor ombrotrophic bog. Still, most fungi and actinobacteria found in the pristine peatland seemed robust to the environmental variables. Both fungal and actinobacterial diversity was higher in the fens than in the bog. Fungal diversity increased significantly after STD whereas actinobacterial diversity did not respond to hydrology. Both fungal and actinobacterial communities became more similar between peatland types after LTD, which was not apparent after STD. Most sequences clustered equally between the two main fungal phyla Ascomycota and Basidiomycota. Sequencing revealed that basidiomycetes may respond more (either positively or negatively) to hydrological changes than ascomycetes. Overall, our results suggest that fungal responses to water-level drawdown depend on peatland type. Actinobacteria seem to be less sensitive to hydrological changes, although the response of some may similarly depend on peatland type.

Summer soil CH 4 emission and uptake in taiga forest near Yakutsk, Eastern Siberia

Summer CH 4 emission and uptake was measured in three contrasting environments (eutrophic lake bank, hummocky mesotrophic fen, forest floor) in taiga forest near the Spasskaya Pad field station (north of Yakutsk, Eastern Siberia). Wet eutrophic lake bank sites showed locally high emission rates (up to 49 mg CH 4 m −2 h −1, average 11.9 mg m −2 h −1). By contrast, fen emissions were an order of magnitude lower despite high water tables. Emission did not exceed 4.2 mg m −2 h −1 (average 1.3 mg m −2 h −1). The emission was highly dependent on water table, slight differences in water table could turn a soil from a source into a sink of CH 4. The dry forest sites show uptake of CH 4 (average 0.4 mg m −2 h −1), even at sites where the water table was situated a few centimeters below the soil surface. A clear relation with water temperature or soil temperature appears to be absent. Also in the wet year of 2006, with higher water table in the forest during the measurement period, CH 4 uptake remained stable. Spatial variation of the uptake fluxes within the site is minimal, but on a larger scale spatial differences are caused by soil texture differences. Our data indicate that the Siberian taiga forest floor is a small sink for CH 4 in the boreal summer.

Membrane probe array: Technique development and observation of CO 2 and CH 4 diurnal oscillations in peat profile

The purpose of this study was to monitor the dynamics of gases such as CO 2 and CH 4 in a soil profile with sufficient temporal resolution to observe possible diurnal variations. A computer-controlled device called a membrane probes array (MPA) was developed that consisted of 9–12 individual membrane probes installed at various soil depths. Each probe was made of a stainless steel pipe with a 1 mm orifice covered with a silicone membrane. Soil gases diffuse through the membrane at a rate proportional to the ambient soil gas concentration. To measure diffusion rates, the probes are flushed with N 2 one-by-one at regular time intervals and accumulated gas is detected as a spike with IR and FID analyzers. The longer the period between flushings the higher the gas accumulation and the lower the detection limit for a particular soil gas. The developed MPA agreed well with conventional manual gas sampling in West-Siberian mesotrophic fen. In peat cores with intact Carex-Sphagnum vegetation incubated under constant temperature, water level and artificial light:dark (14:10) cycles, regular diurnal oscillations of soil CO 2 and CH 4 occurred in the upper part of the peat core down to 19 cm. Gas content in the top layer (3 cm) grew during the light phase, and returned back during the dark phase. In layers further down in the soil, the same events were observed but with progressively increased time delay and lower amplitude. The obtained data agreed with the hypothesis that diurnal variations in soil CO 2 and CH 4 content are caused by periodic changes in intensity of root exudation that provide a major C- and energy source for soil microorganisms including methanogens. At a soil depth of 23 cm, where the peak of gas bubbles occurred, the signal for both gases became chaotic and not related to the light:dark cycle.

Effects of short‐ and long‐term water‐level drawdown on the populations and activity of aerobic decomposers in a boreal peatland

AbstractWe analysed the response of microbial communities, characterized by phospholipid fatty acids (PLFAs), to changing hydrological conditions at sites with different nutrient levels in a southern boreal peatland. Although PLFAs of Gram‐negative bacteria were characteristic of the peatland complex, microbial communities differed among sites (ombrotrophic bog, oligotrophic fen, mesotrophic fen) and sampling depths (0–5, 5–10, 10–20, 20–30 cm). The microbial communities in each site changed significantly following water‐level drawdown. The patterns of change varied among sites and sampling depths. The relative proportion of Gram‐negative bacteria decreased in the upper 10 cm but increased in deeper layers of the fen sites. Fungi benefited from water‐level drawdown in the upper 5 cm of the mesotrophic fen, but suffered in the drier surfaces of the ombrotrophic bog, especially in the 5–10 cm layer. In contrast, actinobacteria suffered from water‐level drawdown in the mesotrophic fen, but benefited in the drier surfaces of the ombrotrophic bog. Basal respiration rate correlated positively with pH and fungal PLFA, and negatively with depth. We suggest that the changes in microbial community structure after persistent water‐level drawdown follow not only the hydrological conditions but also the patterns of vegetation change. Our results imply that changes in structure and activity of the microbial community in response to climate change will be strongly dependent on the type of peatland.