Wet Mire Research Articles

Seismic mapping of on-shore sediments at Andøya, Norway, deposited prior to the North Atlantic rifting

Andøya is an island in the north of Norway. On its eastern side, it contains a local downfaulted basin of Mesozoic sediments sheltered from erosion during subsequent periods of Pleistocene glaciation. The sediments were deposited before the North Atlantic rifting and partly overlie weathered basement. We have recently carried out seismic surveying to better understand the geometry and seismic responses of the basin system. Extensive civil infrastructure and wet mire made the study area challenging for seismic exploration. We shot the survey lines at wet mire with detonating cord during winter when the mire was frozen. In the summer, we conducted seismic surveying along road shoulders with a small-scale vibrator. The seismic processing was particularly challenging due to the influence of traffic noise, heterogeneous near-surface conditions, and large seismic velocity contrasts. We interpreted the seismic lines in integration with other geophysical data and well logs to obtain a consistent and best possible seismic model of the basin. Our interpretation indicates a reorganization of the regional paleostress regime that took place during the continental breakup in the Eocene. In spite of severe obstacles for seismic surveying of the area, our results honor the robustness of the seismic method for subsurface imaging.

Last Millennium hydro-climate variability in Central–Eastern Europe (Northern Carpathians, Romania)

Proxy-based reconstructions of climate variability over the last millennium provide important insights for understanding current climate change within a long-term context. Past hydrological changes are particularly difficult to reconstruct, yet rainfall patterns and variability are among the most critical environmental variables. Ombrotrophic bogs, entirely dependent on water from precipitation and sensitive to changes in the balance between precipitation and evapotranspiration, are highly suitable for such hydro-climate reconstructions. We present a multi-proxy analysis (testate amoebae, plant macrofossils, stable carbon isotopes in Sphagnum, pollen, spores and macroscopic charcoal) from an ombrotrophic peat profile from the Rodna Mountains (northern Romania) to establish a quantitative record of hydro-climatic changes. We identify five main stages: wet surface mire conditions between AD 800 and 1150 and AD 1800 and 1950, and drying of the mire surface between AD 1300 and 1450, AD 1550 and 1750 and AD 1950 and 2012. Our multi-proxy reconstructions suggest that conditions during the Medieval Climate Anomaly (MCA) period (AD 900–1150) were considerably wetter than today, while during most of the ‘Little Ice Age’ (LIA; AD 1500–1850), they were dry. Mire surface conditions in the Rodna Mountains have dried markedly over the last 40 years mainly as a result of anthropogenic climate change approaching the driest conditions seen over the last 1000 years. There is a marked difference between current hydro-climatic conditions (dry mire) and those of the MCA (wet mire). This implies that for the study region, the MCA cannot provide analogous climatic conditions to the contemporary situation. Our reconstructions are in partial agreement with water table estimates elsewhere in central and eastern Europe but generally contrast with those from NW Europe, especially during LIA. We suggest that these distinctive regional differences result from fluctuations in large-scale atmospheric circulation, which determine the relative influences of continental and oceanic air masses.

The soil and plant determinants of community structures of the dominant actinobacteria in Marion Island terrestrial habitats, Sub-Antarctica

Marion Island is a Sub-Antarctic island made up of distinct ecological habitats based on soil physiochemical, plant cover and physical characteristics. The microbial diversity and ecological determinants in this harsh Sub-Antarctic environment are largely uncharacterized. Actinobacteria have diverse ecological functions related to soil and plant functioning. This study was aimed at characterizing the diversity and community structures of the dominant actinobacteria in the distinct habitats and to identify their determinant soil and plant characteristics. Using the 16S rRNA gene, the denaturing gradient gel electrophoresis patterns and clone library diversity were correlated with the soil and plant characteristics. Multivariate statistical methods were also used to identify determinant soil and plant characteristics. Salinity and pH were the most important soil determinants, and a number of important site-specific plant species may have been important. The Coastal Fellfield Habitat was dominated by sequences of the suborders Micrococcineae (44%) and Propionibacterineae (18%), with salinity identified as the principal determinant. The Cotula Herbfield Habitat was dominated by Frankineae (37%) and Streptosporangineae (38%), which were correlated with organic nutrient concentrations. The Wet Mire Habitat was dominated by Acidimicrobineae (61%), with moisture and organic carbon content as principal components. Culture-dependent studies were complementary to culture-independent studies with the majority of actinobacteria isolated not identified in 16S rRNA gene clone libraries. This study demonstrates how the soil physiochemical characteristics and plant species independently determine the community structures of the dominant actinobacteria in distinct ecological habitats. These factors subsequently influence their ecological adaptation, roles and functions.

Erroneous coal maturity assessment caused by low temperature oxidation: Copard, Y. et al. International Journal of Coal Geology, 2004, 58, (3), 171–180

Benched channel samples and continuous block samples of the Hub and Harbour seams from the Sydney Basin, Nova Scotia were studied to define the variations in petrography, geochemistry and palynology of the seams and to interpret the depositional environments of the precursor mires.Petrographic compositions of the seams are very similar with high vitrinite content, low inertinite, moderate liptinite and negligible clastic mineral content. Pyrite content is moderate. There is little variation in petrographic composition between benches in either seam. There are marked variations in petrographic compositions at the lithotype scale. Petrographic facies parameters indicate deposition of the bulk of both seams under fairly uniform conditions in relatively wet mires. Unusually wet or dry periods were rare.The palynological assemblages of both seams indicate a middle to late Westphalian D age. The common to abundant palynomorphs are derived from “arborescent” and “herbaceous” lycopsids, tree ferns and other ferns(?), and sphenopsids. The palynological assemblages support the petrographic interpretation of relatively wet mires. Cordaites pollen (Florinites) is rare, suggesting that there was little contribution from plants growing in dry or upland areas. The absence of the Densospore miospore phase, and the petrographic data, indicate there were no periods in which domed mires occurred.The distinctive dull bands occurring in the Hub and Harbour seams are characterised by low vitrinite contents, high inertinite content, high liptinite and common detrital minerals. Sporinite, showing varying degrees of degradation, is commonly highly concentrated in thin bands. The geochemistry is marked by much higher hi values than normally reported for coals but other indices are typical for coals of this rank. The palynological assemblages of the dull bands are dominated by tree fern spores and other ferns(?) with only a minor contribution by sphenopsid spores. The dull bands were deposited during periods of inundation of mires. Relatively low mineral content indicates that the distributary channels which flooded the mires were quite distant from the depositional sites of the samples.

Vegetation pattern within a thermokarst landscape in the central Altay Mountains (West Siberia)

AbstractIn a mountain basin landscape influenced by a semi‐desert climate in the South Siberian Altay, a geobotanical study was conducted by placing a transect through a run‐off runnel and creating a vegetation map for the wet mire and meadow regions of the study area. The close proximity of semi‐desert and mire associations, formed by thermokarst phenomena, is noteworthy. The associations are presented in terms of their locations, and a phytogeographic classification of species is given. Comparisons with the conditions in NW Mongolia demonstrate the close relationships of dry slopes in the Chuya Basin with the typical Central Asian semi‐desert flora, which extends from the Great Lakes Basin into the southern desert zone of Mongolia. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Wetland classification for Swedish CORINE Land Cover adopting a semi-automatic interactive approach

In a collaboration between the Swedish Space Corporation and the National Land Survey of Sweden, work has been carried out to develop a satellite-data-based method for mapping wetlands for the Swedish CORINE Land Cover database. The aim was two-fold: (1) develop a method for mapping the wetlands in five classes, namely "inland marshes", "wet mires", "other mires", "exploited peatlands", and "salt marshes", with a minimum mapping unit of 1 ha; and (2) investigate if the classes "wet mires" and "other mires" could be obtained more reliably from satellite data than directly from 1 : 50 000 scale topographic maps. Data sources used in the project included geo-referenced Landsat thematic mapper (TM) images, digital topographic map data, digital vegetation data, and colour infrared aerial photographs. The development work included analysis of spectral signature characteristics, classification tests, method definition, method verification, pilot production, and accuracy assessment. The method developed to obtain the five wetland classes is a combination method. The classes inland marshes, salt marshes, and exploited peatlands are mapped using geographical information system (GIS) operations, combining information from the topographic maps, and visual interpretation of Landsat TM data. For the classes wet mires and other mires, a stepwise semi-automatic approach was adopted, where level slicing in ratios or in single Landsat TM bands is used to produce the classes. The evaluation showed high accuracy for all five classes, with overall accuracies ranging from 90% to 100%. It was also concluded that the semi-automatic interactive approach used to produce wet mires and other mires gave the same high accuracy as the topographic map, or a better result than the map for areas in northern Sweden where the representation of wet mires on the map is not as good. The method described is used for production of the wetland classes for the Swedish CORINE Land Cover.

Aapa mires as a carbon sink and source during the Holocene

Summary The vertical and horizontal dynamics of peat carbon accumulation in Ruosuo aapa mire, north‐central Finland, were investigated in an attempt to understand variations in carbon accumulation over time. Paludification began around 8700 BP (9600 cal BP). The long‐term net carbon accumulation rate, based on vertical and lateral growth, was 8.0 g C m−2 year−1. Variations in carbon accumulation rates can be explained to a great extent by natural succession and variations in local conditions, but the role of climate cannot be ignored. The marked decline in carbon accumulation rates after 6100 BP (7000 cal BP) may indicate a relatively dry and warm climate. The levelling out and subsequent increase in carbon accumulation rates after 4000 BP (4500 cal BP) indicates the development of a cooler and moister climate. The low long‐term net carbon accumulation rate and the high carbon content per unit volume in the layer underlying the surficial peat is typical for a wet aapa mire. The continuous penetration of roots, mostly sedge, results in carbon input into the underlying peat layer and contributes to the intensive decay of the surficial peat due to high biological activity. Although one‐third of the apparent carbon has accumulated during the last 2000 years, most of Ruosuo is approaching the stage where primary production does not adequately compensate for overall carbon loss. The declining net carbon accumulation rates from the base up to the depth of 80 cm may indicate a real delayed trend in net carbon accumulation rates. We suggest that under the present climatic conditions the northern circumpolar wet mires are significant sources of greenhouse gases. In addition to high methane production, northern aapa mires also have lower carbon accumulation rates than more southern raised bogs. Our results, which are based on horizontal and vertical carbon accumulation rates, suggest that the earlier published carbon accumulation rates in Finnish aapa mires are overestimated.

Petrographical, palynological and geochemical analyses of the Hub and Harbour seams, Sydney Coalfield, Nova Scotia, Canada—implications for facies development

Benched channel samples and continuous block samples of the Hub and Harbour seams from the Sydney Basin, Nova Scotia were studied to define the variations in petrography, geochemistry and palynology of the seams and to interpret the depositional environments of the precursor mires. Petrographic compositions of the seams are very similar with high vitrinite content, low inertinite, moderate liptinite and negligible clastic mineral content. Pyrite content is moderate. There is little variation in petrographic composition between benches in either seam. There are marked variations in petrographic compositions at the lithotype scale. Petrographic facies parameters indicate deposition of the bulk of both seams under fairly uniform conditions in relatively wet mires. Unusually wet or dry periods were rare. The palynological assemblages of both seams indicate a middle to late Westphalian D age. The common to abundant palynomorphs are derived from “arborescent” and “herbaceous” lycopsids, tree ferns and other ferns(?), and sphenopsids. The palynological assemblages support the petrographic interpretation of relatively wet mires. Cordaites pollen ( Florinites) is rare, suggesting that there was little contribution from plants growing in dry or upland areas. The absence of the Densospore miospore phase, and the petrographic data, indicate there were no periods in which domed mires occurred. The distinctive dull bands occurring in the Hub and Harbour seams are characterised by low vitrinite contents, high inertinite content, high liptinite and common detrital minerals. Sporinite, showing varying degrees of degradation, is commonly highly concentrated in thin bands. The geochemistry is marked by much higher hi values than normally reported for coals but other indices are typical for coals of this rank. The palynological assemblages of the dull bands are dominated by tree fern spores and other ferns(?) with only a minor contribution by sphenopsid spores. The dull bands were deposited during periods of inundation of mires. Relatively low mineral content indicates that the distributary channels which flooded the mires were quite distant from the depositional sites of the samples.

Vertical zonation of Sphagnum mosses along hummock-hollow gradients

The vertical distributions of nine Sphagnum species and four associated mosses in two bogs (Adirondack Mountains, New York) were analyzed for interspecific and interbog differences. Based on 4300 sample points, Sphagnum mean heights ranged from 12 to 43 cm above the water table and the sequence of species was similar in both bogs (S. cuspidatum and S. majus) < (S. fallax and S. angustifolium) < (S. magellanicum, S. rubellum, and S. russowii) < (S. fuscum and S. nemoreum). However, at Bloomingdale Bog, a relatively dry mire with many well-developed hummocks and narrow hollows, mosses had significantly greater means (by 4-12 cm) than at Raybrook Bog, a relatively wet mire with wide Sphagnum carpets and fewer hummocks. South- and east-facing hummock slopes tended to be gentler than the north and west slopes, but the mosses’ mean heights did not vary with aspect. The abundance of hummocks at Bloomingdale seems responsible for not only the greater mean heights, but also for broader ranges and greater vertical overlap with other species. However, the ability of each species to dominate a certain array of height classes did not differ between bogs. Within each bog, hummock species tended to have larger vertical ranges than hollow species, implying a lesser ability of hollow mosses to tolerate the full range of conditions along the hummock-hollow gradient.