| 1. |
- Alekseychik, Pavel, et al.
(författare)
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Surface energy exchange in pristine and managed boreal peatlands
- 2018
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Ingår i: Mires and Peat. - 1819-754X. ; 21
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Tidskriftsartikel (refereegranskat)abstract
- Surface–atmosphere energy exchange is strongly ecosystem-specific. At the same time, as the energy balance constitutes responses of an ecosystem to environmental stressors including precipitation, humidity and solar radiation, it results in feedbacks of potential importance for the regional climate. Northern peatlands represent a diverse class of ecosystems that cover nearly 6 × 106 km2 in the Boreal region, which makes the inter-comparison of their energy balances an important objective. With this in mind we studied energy exchange across a broad spectrum of peatlands from pristine fens and bogs to forested and agriculturally managed peatlands, which represent a large fraction of the landscape in Finland and Sweden. The effects of management activities on the energy balance were extensively examined from the micrometeorological point of view, using eddy covariance data from eight sites in these two countries (56º 12'–62º 11' N, 13º 03'–30º 05' E). It appears that the surface energy balance varies widely amongst the different peatland types. Generally, energy exchange features including the Bowen ratio, surface conductance, coupling to the atmosphere, responses to water table fluctuations and vapour pressure deficit could be associated directly with the peatland type. The relative constancy of the Bowen ratio in natural open mires contrasted with its variation in tree-covered and agricultural peatlands. We conclude that the impacts of management and the consequences of land-use change in peatlands for the local and regional climate might be substantial.
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| 2. |
- Backéus, Ingvar, 1945-, et al.
(författare)
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Bog vegetation re-mapped after 63 and 103 years : expansion of Rhynchospora alba (Studies on Skagershultsmossen 2)
- 2023
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Ingår i: Mires and Peat. - : International Mire Conservation Group and International Peatland Society. - 1819-754X. ; 29, s. 1-16
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Tidskriftsartikel (refereegranskat)abstract
- The vegetation in an area of the ombrotrophic bog Skagershultsmossen, South-Central Sweden, was mapped in 2010. The same area was previously surveyed in 1907 and 1970. Only small changes were found in 1970, in contrast to the situation in 2010, when a large shift in the vegetation was observed. The previously dominating vegetation type, lawns dominated by Eriophorum vaginatum, had more or less disappeared and was replaced by carpet vegetation dominated by Rhynchospora alba, Sphagnum tenellum and S. balticum. Also, the carpets dominated by Scheuchzeria palustris had decreased to a large extent. There are several possible climatic explanations behind the changes, and we suggest that increased frost action linked to the reduction in snow cover may be important. The shift in the vegetation has most certainly led to a decrease in peat productivity and, hence, a reduction in carbon sequestration by the bog is assumed. Skagershultsmossen is an important reference site for future studies of long-term vegetation changes.
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| 3. |
- Franzén, Lars, 1950, et al.
(författare)
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Microscopic charcoal and tar (CHAT) particles in peat : a 6500-year record of palaeo-fires in southern Sweden
- 2012
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Ingår i: Mires and Peat. - 1819-754X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Peat stratigraphies of eleven raised bogs in southern Sweden were investigated. Measurements included the occurrence of charcoal and various tar particles. Most of the particles found were microscopic, i.e. 5-100 mu m in diameter. Two distinctly different groups of particles were distinguished: (A) charred fragments of plant tissue and (B) objects formed from tar, which were classified into five sub-groups on the basis of morphology. Both charcoal and tar are indicative of mire and forest fires. We suggest that it is possible to use the different groups of particles as fire regime indicators. Hence, the high frequency of charcoal and tar (CHAT) in the lower parts of the stratigraphies, i.e. in the lower strongly decomposed fen and carr peats that were formed before ca. 4000 cal C-14 BP, could be indicative of intense and frequent local fires. The decreasing abundance of CHAT and the lower relative share of Type A particles within the lower strongly decomposed Sphagnum peat ca. 4000-2500 cal C-14 BP signify a transition from local to regional fires. With a few exceptions, the uppermost weakly decomposed ombrotrophic peats formed after ca. 2500 cal C-14 BP, in which both charcoal and tar are rare, indicate a period of low fire frequency at both local and regional scales. There is no regional variation in the lower material, and it seems that wildfires were common phenomena throughout southern Sweden during the first few thousand years after peat formation began 6-8000 years ago. From a climatological point of view, the mass occurrence of CHAT in the lower parts of the profiles indicates a warm and dry Mid Holocene with frequent and widespread wildfires, and a moist and cool Late Holocene with more sporadic fires. Spectral analysis of the entire dataset shows significant periodicities of 610, 70, 30, 21, 17 and 14 years, the two most significant being 14 and 70 years.
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| 4. |
- Franzén, Lars, 1950
(författare)
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ncreased decomposition of subsurface peat in Swedish raised bogs
- 2006
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Ingår i: Mires and Peat. - 1819-754X. ; 1:3
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Tidskriftsartikel (refereegranskat)abstract
- An increased rate of decomposition has been observed in a large number of raised bogs in southern Sweden and elsewhere since the 1970s. The effect is manifest as a discoloured and mucous subsurface peat layer, and there is associated subsidence of mire surfaces. This paper reports the results of a systematic investigation of the phenomenon in 14 raised bogs in southern Sweden, which was carried out between 1997 and 2005. Degree of decomposition, bulk density and ash content were measured and evidence of surface subsidence over recent decades was collected. Shallow peat layers of ‘normal’ appearance could not be found anywhere within the study sites, and all showed the same signs of secondary decomposition. In particular, the ombrotrophic parts of the Komosse Bog Complex appeared to have subsided by at least 150 mm over the last 35 years, i.e. at a rate of approximately 4.3 mm per annum, which is more than four times the average rate of peat formation in circumboreal raised bogs. The changes observed could have been caused by change in any one of a number of factors, e.g. climate, hydrology and rate of nutrient supply; or by a combination of such factors. However it seems most likely that they are attributable to the heavy modern nutrient load, e.g. of dust from anthropogenic sources. There is cause for concern that many high-latitude peatlands may consequently have switched over from being net sinks, to net sources, of atmospheric carbon
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| 5. |
- Franzén, Lars, 1950, et al.
(författare)
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The potential peatland extent and carbon sink in Sweden, as related to the Peatland / Ice Age Hypothesis
- 2012
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Ingår i: Mires and Peat. - 1819-754X. ; 10:artikel nr 08, s. 1-19
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Tidskriftsartikel (refereegranskat)abstract
- Peatlands cover approximately 65,600 km2 (16 %) of the Swedish land area. The available areas suitable for peatland expansion are far from occupied after ca. 12,000 years of the present interglacial. We estimate the potential extent of peatland in Sweden, based on slope properties of possible areas excluding lakes and glaciofluvial deposits. We assume no human presence or anthropic effects, so the calculation is speculative. It may have been relevant for previous interglacials. We calculate the potential final area of peatlands in three scenarios where they cover all available land with different maximum slope angles (1−3 º) using a Digital Elevation Model (DEM). The three scenarios yield potential peatland areas of 95,663 km2 (21 % of total available area), 168,287 km2 (38 %) and 222,141 km2 (50 %). The relative increases from the present 65,600 km2 are 46, 157 and 239 % respectively. The slope scenarios give CO2 uptake rates of 8.9−10.8, 18.1−22.4 and 24.6−30.5 Mt yr−1. Under global warming conditions with isotherms moved northwards and to higher altitudes, following an increase of raised bog area, the CO2 uptake rates might increase to 12.2−13.8, 24.4−27.7 and 33.5−37.9 Mt yr−1; i.e. up to 4.3−4.9 vpb of atmospheric CO2. If we make the speculative extrapolation from Sweden to all high latitude peatlands, and assume that all suitable areas with slope angle ≤ 3 ° become occupied, the global peatland CO2 sink might approach 3.7 Gt yr−1 (about 2 vpm yr−1) and potentially cause a net radiative cooling approaching 5 W m−2.
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| 6. |
- Jordan, Sabine, et al.
(författare)
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Ecosystem respiration, methane and nitrous oxide fluxes from ecotopes in a rewetted extracted peatland in Sweden
- 2016
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Ingår i: Mires and Peat. - 1819-754X. ; 17
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Tidskriftsartikel (refereegranskat)abstract
- Ecosystem respiration (carbon dioxide; CO2), methane (CH4) and nitrous oxide (N2O) fluxes to the atmosphere were determined using an opaque closed chamber method within various ecotopes (vegetation covered, bare peat and open water) in a rewetted extracted peatland and within an adjacent open poor fen in Sweden. Ecotopes had a significant impact on CO2 and CH4 fluxes to the atmosphere. Ecosystem respiration and CH4 emissions from the bare peat site, the constructed shallow lake and the open poor fen were low but were much higher from ecotopes with Eriophorum vaginatum tussocks and Eriophorum angustifolium. A combination of vascular plant cover and high soil temperatures enhanced ecosystem respiration, while a combination of vascular plant cover, high water table levels and high soil temperatures enhanced CH4 emissions. N2O emissions contributed little to total greenhouse gas (GHG) fluxes from the soil-plant-water systems to the atmosphere. However, the overall climate impact of CH4 emissions from the study area did not exceed the impact of soil and plant respiration. With regard to management of extracted peatlands, the construction of a nutrient-poor shallow lake showed great potential for lowering GHG fluxes to the atmosphere.
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| 7. |
- Koebsch, Franziska
(författare)
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From meadow to shallow lake: Monitoring secondary succession in a coastal fen after rewetting by flooding based on aerial imagery and plot data
- 2017
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Ingår i: Mires and Peat. - 1819-754X. ; 19
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Tidskriftsartikel (refereegranskat)abstract
- Year-round flooding can be a cost-effective measure for rewetting highly degraded fens, and is gaining popularity for lowland fen restoration in Europe. We investigated the short-term effects of such permanent inundation on species composition and spatial distribution of the vegetation of a formerly drained coastal fen, and addressed the question of whether re-establishment of peat-forming reed vegetation is foreseeable. For vegetation mapping and monitoring we combined permanent plot data acquired during four years following shallow flooding, high-resolution aerial imagery and an elevation model. Five vegetation types were distinguished, and we analysed their spatial distribution and succession patterns throughout the years. Preexisting vegetation, its spatial arrangement and the water level played major roles in secondary succession. Existing patches of Phragmites australis showed high stability, but their growth was not consistent through the years and at all inundation depths. Existing stands of Bolboschoenus maritimus were outcompeted by Schoenoplectus tabernaemontani or vanished and formed relatively stable ponds of open water with hydrophytic species. We concluded that the expansion of reed as peat-forming vegetation is likely to proceed slowly, but fluctuations in water level and edge effects will probably maintain a persistent mosaic of vegetation and open water in the near future.
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| 8. |
- Lode, Elve
(författare)
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Indicative effects of climate change on groundwater levels in Estonian raised bogs over 50 years
- 2017
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Ingår i: Mires and Peat. - 1819-754X. ; 19
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Tidskriftsartikel (refereegranskat)abstract
- Analyses of 50-year (1962-2011) monthly air temperature and precipitation data indicated substantial climate change in the locations of two raised bogs (Linnusaare and Mannikjarve) in central-east Estonia. During recent years the cross-year winter air temperature increased by 1.7 degrees C, while the cold-season precipitation increased by 4 mm. The fluctuation amplitude of temperature and precipitation values decreased. Snow depth proved to be the most sensitive variable to winter warming, followed by groundwater levels together with mean and maximum soil frosts. Long-term groundwater levels on the domes of the bogs and in the forested/treed lagg areas were 0.3-0.4 m and 0.4-0.8 m below the soil surface, respectively. Warming caused changes in groundwater level amplitude of 3-22 cm in the bog domes and 3-14 cm in the forested lagg zones. The lowest groundwater levels in ridge-pool ecotopes at Mannikjarve rose by 6-10 cm (i.e. these ecotopes became wetter); but the incidence of low groundwater levels increased in most ecotopes, indicating a more general trend towards drier conditions in the bog.
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| 9. |
- Lundin, Lars
(författare)
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Revegetation dynamics after 15 years of rewetting in two extracted peatlands in Sweden
- 2016
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Ingår i: Mires and Peat. - 1819-754X. ; 18
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Tidskriftsartikel (refereegranskat)abstract
- The restoration of extracted peatlands poses challenges with regard to their recolonisation by vegetation. The most significant problems are unstable water levels, destroyed propagule bank, and temperature fluctuations on bare peat surfaces. Rewetting is considered necessary for the re-establishment of peat-forming vegetation. Revegetation was investigated in a long-term field study at two rewetted extracted peatland sites in south-central Sweden, namely Västkärr (originally a lagg fen) and Porla (originally a bog). Both sites were expanses of bare peat before rewetting.Rewetting procedures were applied in 1999 and strongly promoted plant colonisation. At Västkärr, colonisation started in the first year after rewetting, mostly by species that were not found during repeat vegetation surveys 15 years later. By 2014, Västkärr was a shallow lake surrounded by mesotrophic and eutrophic vegetation with species such as Carex rostrata, Lemna minor, Typha latifolia, Phalaris arundinacea and Phragmites australis. Revegetation of the Porla site was slower and started with Eriophorum vaginatum and Polytrichum spp. Sphagnum mosses appeared after six years and had established quite well after 13 years. A residual Sphagnum peat layer, inflowing surface water and groundwater provided spatially variable nutrient conditions. Sphagnum species and E. vaginatum established in nutrient-poor areas, while C. rostrata, P. australis and Eriophorum angustifolium colonised more nutrient-rich locations.
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| 10. |
- Malmer, Nils
(författare)
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On the relations between water regime, mass accretion and formation of ombrotrophic conditions in Sphagnum mires
- 2014
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Ingår i: Mires and Peat. - 1819-754X. ; 14, s. 07-07
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Tidskriftsartikel (refereegranskat)abstract
- (1) I explore the hypothesis that the water regime is one of the major determinants of the difference between bog and fen in Sphagnum mires because of its effects on the decay loss and the mass accretion rate. This article deals with the recent mass balance and water regime and the variation in mass accretion rate during the last millennium, studied at two mires in southern Sweden. (2) At one bog site and one fen site in the Akhult mire the recent litter input to the acrotelm and mass accretion in the catotelm were 210 and 38 g m(-2) a(-1) at the bog site and 300 and 21 g m(-2) a(-1) at the fen site, respectively. The difference in productivity reflected the availability of plant nutrients and the pH. The smaller loss of mass at the bog site was a result of smaller water table amplitude and a higher median time water level (MTWL) than at the fen site. Through its effects on hummock formation, the water regime is also a major determinant of the surface structure. (3) Around 1000 cal. BP the precipitation and the supply of mineral soil water to the two sites increased and the bog vegetation of that time was replaced by fen vegetation. Mass accretion first increased to 180 g m(-2) a(-1) but with the upward growth of the mire surface the rate decreased. The recent conditions at the fen site became established similar to 800 cal. BP, probably as a result of increased water table amplitudes. At the bog site the water regime changed from geogenous to ombrogenous similar to 600 cal. BP, contemporary with a decrease in precipitation. This change resulted in a rapid increase in mass accretion by 150 % followed by a slow decrease until recent times with low values. The same development was found to have occurred twice at the Store Mosse mire. Such an initial increase in the peat accretion rate must be important for the formation of permanently ombrotrophic conditions in raised bogs.
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| 11. |
- Marti, M., et al.
(författare)
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Strong long-term interactive effects of warming and enhanced nitrogen and sulphur deposition on the abundance of active methanogens in a boreal oligotrophic mire
- 2019
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Ingår i: Mires and Peat. - Dundee, United Kingdom : Mires and Peat. - 1819-754X. ; 24, s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- Peatlands play a key role in the carbon cycle by being a considerable source of atmospheric methane. Thus, an understanding of the microbial production of methane is important in relation to environmental changes of peatlands. We applied real-time PCR on the mcrA gene and transcript to investigate the peat methanogen community response to the combined effect of 18 years of simulated warming and deposition of nitrogen (N) and sulphur (S) at a boreal oligotrophic mire in Sweden. The long-term effects of the experimental treatments on the methanogens was highly dependent on interactions between the treatment factors Enhanced N deposition amplified the effect of warming, resulting in a further increase of the abundance of active methanogens. The effect of the perturbations was modulated by the depth horizon, with the strongest effect at the water level, where the interaction between enhanced N and S deposition, and warming, resulted in an increase of active methanogens. These results indicate that increasing average temperatures and simultaneously higher N deposition rates will substantially increase the methanogenic activity in northern ombrotrophic peatlands. These findings strongly highlight the importance of accounting for any possible interactive perturbation effects when investigating the response of peat methanogens to environmental change.
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| 12. |
- Norberg, Lisbet, et al.
(författare)
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Impact of drainage and soil properties on carbon dioxide emissions from intact cores of cultivated peat soils
- 2018
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Ingår i: Mires and Peat. - 1819-754X. ; 21
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Tidskriftsartikel (refereegranskat)abstract
- Drained peatlands contribute to anthropic emissions of carbon dioxide (CO2), so a better understanding of the underlying processes and identification of mitigation options for agricultural peatlands are urgently required. Peatland soil properties vary greatly and, in combination with drainage, can affect emissions of CO2 both directly and indirectly. Drainage reduces soil water content but increases CO2 production, so it is important to find the optimum drainage level that minimises CO2 emissions without affecting agricultural use. Intact soil cores from nine different sites (topsoil, plus subsoil at four sites) were collected and brought into a controlled laboratory environment. Repeated measurements of CO2 fluxes were performed at increasing soil water suctions corresponding to different drainage levels. Physical and chemical properties of the soils were determined and compared with the CO2 emissions. The soil cores displayed different CO2 emission patterns with increasing soil water suction head. In some cores, emissions increased rapidly to a high level, while in others they remained at lower levels. At a soil water suction head of only 0.5 m of water, the average soil CO2 emissions had already reached a maximum. The soil cores represented peat soils with a wide range of soil properties, e.g. bulk density from 0.17 to 0.47 g cm(-3) and total carbon from 26.3 to 43.5 %, but none of the properties measured was clearly correlated with CO2 emissions.
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| 13. |
- Ratcliffe, Joss
(författare)
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Multi-substrate induced respiration (functional capacity) in agriculturally degraded and intact restiad bogs: implications for carbon and nitrogen cycling
- 2020
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Ingår i: Mires and Peat. - 1819-754X. ; 26
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Tidskriftsartikel (refereegranskat)abstract
- Natural peatlands provide ecosystem services such as carbon storage and habitat, which can be negatively affected (degraded) by the proximity of agricultural land due to lowered water table and increased nutrient deposition. We assessed peat biochemistry and microbial function in the dry, fluctuating and saturated zones of the peat deposits at Moanatuatua (degraded) and Kopuatai (intact) raised bogs in New Zealand to investigate the effects of adjacent agriculture on carbon (C) and nitrogen (N) cycling. Peat C and N density were elevated, due in part to greater bulk density, in the dry and saturated zones at Moanatuatua compared with Kopuatai. Functional capacity (multi-substrate induced respiration) at Moanatuatua was greater than at Kopuatai, and water-soluble C was at lower concentration but more degradable, indicating that microbes were C limited at Moanatuatua but N limited at Kopuatai. Greater microbial function at Moanatuatua infers C inputs may be more rapidly converted to gaseous or waterborne exports, and agriculturally affected peatlands may be more susceptible to losses of labile C. We conclude that proximity to agriculture is likely to have caused changes in chemical properties and altered microbial functioning of restiad bog and has important implications for C and N turnover within these peatland systems.
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