Palsas and Peat Plateaus in Central Manitoba and Saskatchewan

1972 ◽  
Vol 2 (3) ◽  
pp. 291-302 ◽  
Author(s):  
S. C. Zoltai
Keyword(s):  
Volume Change ◽  
Developmental Stages ◽  
Present Climate ◽  
Southern Limit ◽  
Discontinuous Permafrost ◽  
Flin Flon ◽  
Peat Plateaus

Twenty-six peat plateaus and eight palsas were examined near Flin Flon, Manitoba at the southern limit of discontinuous permafrost. Peat plateaus in different developmental stages were identified on the basis of their morphology. The permafrost is entirely within the peat in all peat plateaus within the study area, but extends into mineral subsoil under all palsas examined. Doming in peat plateaus is largely explained by volume change due to change from unfrozen to frozen stage, and by buoyancy of the frozen mass floating on unfrozen peat. The occurrence of aggrading and degrading peat plateaus in the same area indicates that all developmental stages are permitted by the present climate.

The evolution of permafrost in the taiga and in the forest–tundra, western Quebec–Labrador Peninsula

1976 ◽  
Vol 6 (2) ◽  
pp. 203-220 ◽  
Author(s):  
Serge Payette ◽  
Hélène Samson ◽  
Daniel Lagarec
Keyword(s):  
Developmental Stages ◽  
Hudson Bay ◽  
James Bay ◽  
Forest Tundra ◽  
Discontinuous Permafrost ◽  
Latitudinal Shift ◽  
Shrub Tundra ◽  
Forest Microclimate ◽  
Southern Section ◽  
Peat Plateaus

Major permafrost landforms of the discontinuous permafrost zone of Hudson Bay and James Bay, Quebec–Labrador Peninsula, are described and interpreted within an ecological perspective. These landforms are not fossil permafrost bodies; they are presently evolving under aggrading and degrading developmental stages. Permafrost peat complexes and permafrost mineral complexes are differentially distributed in the midtaiga, the forest–tundra, and the shrub–tundra zones of the study area. The wooded palsa complex is the most obvious permafrost complex in the midtaiga, and the palsa complex in the forest–tundra: The wooded palsa complex is related to the forest chronosequence, whereas the palsa complex, farther north, occurs where there is a suitable macroclimate for permafrost aggradation without the influence of cool forest microclimate. The wooded cryogenic mound complex in mineral landform is mainly distributed in the southern section of the forest–tundra and near the Hudson Bay shore; the cryogenic mineral mound complex is found in the northern section. The latitudinal shift of the northern complex is necessary for permafrost initiation in open sites. Degrading stages associated with thermokarst activity are similar for all these landforms and it is suggested that palsa complex is made of incipient, mature, and residual palsas whether they belong to palsa mounds or to peat plateaus. Similar conclusions are valid for cryogenic mineral mound complex.

Effects of Warming and Permafrost Thaw on Carbon Dioxide Fluxes from Boreal Peatlands in northwestern Canada

2021 ◽  
Author(s):  
Christopher Schulze ◽  
David Olefeldt ◽  
Natascha Kljun ◽  
Laura Chasmer ◽  
Chris Hopkinson ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Ecosystem Respiration ◽  
Carbon Dioxide Fluxes ◽  
Southern Limit ◽  
Permafrost Thaw ◽  
Boreal Peatlands ◽  
Discontinuous Permafrost ◽  
Southern Site ◽  
Footprint Analysis ◽  
Peat Plateaus

<p>The Taiga Plains ecozone in northwestern Canada is warming rapidly which alters the carbon dioxide (CO<sub>2</sub>) fluxes of the boreal peat landscape in two ways: 1) directly by increasing temperatures going along with increasing fluxes and 2) indirectly via permafrost thaw and resulting wetland expansion. However, we still lack an understanding of how direct and indirect effects vary across a latitudinal climate gradient covering different extents of permafrost. In this study, we will compare two years of concurrent eddy covariance measurements made over forested permafrost peat plateaus at Smith Creek (discontinuous permafrost) and Scotty Creek (sporadic permafrost) to assess differences in net CO<sub>2</sub> exchange and its two component fluxes, gross primary productivity (GPP) and ecosystem respiration (ER). Footprint analysis will be used to assess the net CO<sub>2</sub> balance of peat plateaus and thermokarst wetlands at both sites. We hypothesize that GPP and ER will be higher at the warmer Scotty Creek site, due to both, more abundant thermokarst wetlands and higher GPP and ER of peat plateaus at this southern site. We also hypothesize that the effects of warming on GPP are greater than on ER and thus that the warmer Scotty Creek site is a greater net CO<sub>2</sub> sink. Our study will conclude on the carbon feedback of warming peat landscapes near the southern limit of permafrost in northwestern Canada in response to Climate Change.</p>

A thawing boreal peat landscape along the southern limit of permafrost presently is carbon neutral

2020 ◽  
Author(s):  
Oliver Sonnentag ◽  
Julien Fouché ◽  
Manuel Helbig ◽  
Gabriel Hould Gosselin ◽  
Matteo Detto ◽  
...  
Keyword(s):  
Land Cover ◽  
Eddy Covariance ◽  
Black Spruce ◽  
Mean Value ◽  
Permafrost Region ◽  
Southern Limit ◽  
Organic C ◽  
Land Cover Types ◽  
Ecosystem Carbon ◽  
Peat Plateaus

<p>Along the southern limit of permafrost in northwestern Canada rising air temperatures have caused widespread land cover changes at unprecedented rates. A prominent change includes thermokarst wetland expansion at the expense of black spruce-dominated boreal forest stands due to the permafrost thaw-induced collapse of peat plateaus. We present a multi-year (2013 – 2017) net ecosystem carbon (C) balance (NECB, g C m<sup>-2</sup>year<sup>-1</sup>) at Scotty Creek near Fort Simpson, NT. The highly fragmented study site is dominated by permafrost-free wetlands and forested permafrost peat plateaus. Eddy covariance  measurements of net ecosystem carbon dioxide (CO<sub>2</sub>) and methane (CH<sub>4</sub>) exchanges (2013 – 2017) are complemented by discharge (2014 – 2016) and water chemistry monitoring (2015 and 2016) at the outlets of three small headwater catchments (<0.5 km<sup>2</sup>) draining the eddy covariance footprint area. In addition to net ecosystem CO<sub>2</sub>and CH<sub>4</sub>exchanges, the NECB includes the export of dissolved C (DC) as the sum of inorganic and organic C (DIC and DOC), free CO<sub>2</sub>and CH<sub>4</sub>through runoff, and the estimated import of DOC through precipitation. We use absorbance spectroscopy for dissolved organic matter (DOM) characterization to distinguish different DOM sources among catchments and characteristic land cover types. Between 2013 and 2017, the NECB varied between a weak net C source (~16 ±5 g C m<sup>-2</sup>year<sup>-1</sup>) and sink (~-22 ±5 g C m<sup>-2</sup>year<sup>-1</sup>) in 2015 and 2013, respectively, with a mean value of -1 ±7 g C m<sup>-2</sup>year<sup>-1</sup>. The net C sink-source strength was largely controlled by variations in net CO<sub>2</sub>exchange, ranging between a weak net CO<sub>2 </sub>sink (~-29 ±3 g C m<sup>-2</sup>year<sup>-1</sup>) and source (~8 ±4 g C m<sup>-2</sup>year<sup>-1</sup>) in 2015 and 2013, respectively. In contrast, our study site was a persistent annual net CH<sub>4</sub>source (~8 ±1 g C m<sup>-2</sup>year<sup>-1</sup>). Compensated by the import of DOC through precipitation, DC exported from the three catchments was a negligible component of the NECB. There were no significant differences in DOC concentrations and absorbance indices among catchments, and thawed and frozen land cover types, overall illustrating high DOM aromaticity (SUVA<sub>254</sub>= 3.3 ± 0.6 L mg<sup>-1</sup>m<sup>-1</sup>) and high molecular weight (a254:a365 = 4.3 ± 0.3) characteristic for peatlands and peat-dominated landscapes outside the circumpolar permafrost region. We conclude that a rapidly thawing boreal peat landscape along the southern limit of permafrost presently appears to be C neutral.</p>

The Holocene evolution of permafrost near the tree line, on the eastern coast of Hudson Bay (northern Quebec)

1987 ◽  
Vol 24 (11) ◽  
pp. 2206-2222 ◽  
Author(s):  
Michel Allard ◽  
Maurice K. Seguin
Keyword(s):  
Climatic Conditions ◽  
Snow Accumulation ◽  
Eastern Coast ◽  
Permafrost Degradation ◽  
Tree Line ◽  
Stratigraphic Sequence ◽  
Forest Tundra ◽  
Discontinuous Permafrost ◽  
Shrub Tundra ◽  
Peat Plateaus

Permafrost evolution in postglacial marine silts near the tree line was reconstructed using landform analysis, 14C dating, and palynostratigraphic analysis of peat sections. In the forest–tundra, below the tree line, four sites in peat plateaus have a stratigraphic sequence indicating an alluvial plain environment from 6000 to 4800 BP followed by a wetland supporting trees and shrubs with deep snow accumulation and without permafrost. Ground heave occurred between 1900 and 1200 BP as peat plateaus and palsas were formed. In the shrub–tundra, above the tree line, three permafrost sites with buried peat beds suggest that climatic conditions were cold enough for discontinuous permafrost in the surrounding landscape starting from land emergence, about 5800 BP; however, fen expansion and sedge peat accumulation continued over unfrozen ground until 2300, 1560, and 1400 BP. At these dates, the sites were buried with silt, probably as a result of mass wasting on nearby permafrost mounds and then permafrost aggraded under the sites. Generally, the palynostratigraphic data reflect a marked cooling of climate starting by 3200–2700 BP and culminating in a major period of permafrost aggradation between 1900 and 1200 BP. Permafrost degradation has been dominant since then despite other possible cold intervals. Nowadays, the permafrost in marine silts is twice as thick and three times more widespread in the shrub–tundra than in the forest–tundra.

Évolution récente d'une tourbière à palses (Québec subarctique) : analyse cartographique et dendrochronologique

1988 ◽  
Vol 66 (11) ◽  
pp. 2217-2227 ◽  
Author(s):  
Danielle Laprise ◽  
Serge Payette
Keyword(s):  
Tree Ring ◽  
Developmental Stages ◽  
Black Spruce ◽  
Eastern Coast ◽  
Reaction Wood ◽  
Permafrost Degradation ◽  
Pool Surface ◽  
Autocatalytic Process ◽  
Ring Analysis ◽  
Peat Plateaus

During the past 100 years, palsa bogs located on the eastern coast of Hudson Bay have undergone major changes associated with global climatic warming of the northern hemisphere. The recent main developmental stages of palsas, collapse scars, and thermokarstic pools were reconstructed within a representative permafrost peatland located in the southern part of the forest–tundra, using detailed mapping and tree-ring analyses. Maps of the peatland in 1957, 1973, and 1983 indicate a 49% decrease of the total cover of palsas and collapse scars between 1957 and 1983 and a 44% increase of the thermokarstic pool surface. Degradation of the palsa bog was more pronounced between 1957 and 1973 than between 1973 and 1983. Tree-ring analysis of reaction wood on black spruce (Picea mariana (Mill.) BSP.) exposed to unstable peat substratum indicates that permafrost degradation, which began as early as 1880, increased markedly between 1930 and 1965. During the 19th century, the permafrost peatland was mainly composed of large peat plateaus, which subsequently disintegrated into residual palsas, collapse scars, and thermokarstic pools. In addition the increase in temperature during the 20th century, it seems that milder winters with heavier snowfalls promoted conditions conducive to permafrost degradation. The constantly increasing contrast in the microtopographic pattern of the peatland, resulting from the transformation of peat plateaus into smaller palsa units, created more snow cover on east and southeast palsa slopes, thus accelerating permafrost degradation. This autocatalytic process seems to have also played a role in some sections of the peatland with abundant thermokarstic pools, where major changes in drainage conditions have stimulated thermokarstic erosion.

scholarly journals Vulnerability of the Ancient Peat Plateaus in Western Siberia

Plants ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 2813
Author(s):  
Alexander Pastukhov ◽  
Tatiana Marchenko-Vagapova ◽  
Sergey Loiko ◽  
Dmitry Kaverin
Keyword(s):  
Western Siberia ◽  
Hydrological Regime ◽  
Anthropogenic Disturbances ◽  
Permafrost Degradation ◽  
Peat Accumulation ◽  
Southern Limit ◽  
Current State ◽  
Peat Deposits ◽  
Under Construction ◽  
Peat Plateaus

Based on the data of the plant macrofossil and palynological composition of the peat deposits, the evolution and current state of polygonal peatlands were analyzed at the southern limit of continuous permafrost in the Pur-Taz interfluve. Paleoreconstruction shows that peat accumulation began in the Early Holocene, about 9814 cal. year BP, in the Late Pre-Boreal (PB-2), at a rate of 1 to 1.5 mm year−1. Intensive peat accumulation continued in the Boreal and early Atlantic. The geocryological complex of polygonal peatlands has remained a stable bog system despite the predicted warming and increasing humidity. However, a rather rapid upper permafrost degradation and irreversible changes in the bog systems of polygonal peatlands occur with anthropogenic disturbances, in particular, a change in the natural hydrological regime under construction of linear objects.

Les formes de glaces des grottes de la Nahanni, Territoires du Nord-Ouest, Canada

1977 ◽  
Vol 14 (5) ◽  
pp. 1179-1185 ◽  
Author(s):  
J. Schroeder
Keyword(s):  
Karst Region ◽  
Karst System ◽  
American Continent ◽  
Southern Limit ◽  
North American Continent ◽  
The North ◽  
Hexagonal Ice ◽  
Discontinuous Permafrost ◽  
Subarctic Climate

Exploration has been continuing on the karst system developed within the cliffs of the First Canyon (300–1050 m deep) of the South Nahanni River(61°18′ N, 124°10′ W). Probably the most northerly on the North American continent, this karst region is within the discontinuous permafrost zone, at the southern limit of the tundra. The caves contain ice of the type which depends on the present subarctic climate (two-dimensional hexagonal ice crystals, ice like calcite speleothem and 'secondary' ice), or on a long-term climatic change of ± 2400 years (massive ice deposits and sponge-like ice deposits).

Correlated Studies of Cellular Interactions Using TEM, Freeze Etching, and SEM

1974 ◽  
Vol 32 ◽  
pp. 320-321
Author(s):  
J. P. Revel
Keyword(s):  
Developmental Stages ◽  
Three Dimensional ◽  
Cell Movement ◽  
Cellular Interactions ◽  
Serial Sections ◽  
Cell Sheets ◽  
Freeze Etching ◽  
Early Developmental

Movement of individual cells or of cell sheets and complex patterns of folding play a prominent role in the early developmental stages of the embryo. Our understanding of these processes is based on three- dimensional reconstructions laboriously prepared from serial sections, and from autoradiographic and other studies. Many concepts have also evolved from extrapolation of investigations of cell movement carried out in vitro. The scanning electron microscope now allows us to examine some of these events in situ. It is possible to prepare dissections of embryos and even of tissues of adult animals which reveal existing relationships between various structures more readily than used to be possible vithout an SEM.

Electron investigations of rhabdovirus-like particles in mexican bean beetles and crickets

1978 ◽  
Vol 36 (2) ◽  
pp. 378-379
Author(s):  
J. R. Adams ◽  
G. J Tompkins ◽  
A. M. Heimpel ◽  
E. Dougherty
Keyword(s):  
Biological Control ◽  
Integrated Pest Management ◽  
Pest Management ◽  
Developmental Stages ◽  
Management Program ◽  
Acheta Domesticus ◽  
Epilachna Varivestis ◽  
House Cricket ◽  
Similar Morphology ◽  
Bean Beetle

As part of a continual search for potential pathogens of insects for use in biological control or on an integrated pest management program, two bacilliform virus-like particles (VLP) of similar morphology have been found in the Mexican bean beetle Epilachna varivestis Mulsant and the house cricket, Acheta domesticus (L. ).Tissues of diseased larvae and adults of E. varivestis and all developmental stages of A. domesticus were fixed according to procedures previously described. While the bean beetles displayed no external symptoms, the diseased crickets displayed a twitching and shaking of the metathoracic legs and a lowered rate of activity.Examinations of larvae and adult Mexican bean beetles collected in the field in 1976 and 1977 in Maryland and field collected specimens brought into the lab in the fall and reared through several generations revealed that specimens from each collection contained vesicles in the cytoplasm of the midgut filled with hundreds of these VLP's which were enveloped and measured approximately 16-25 nm x 55-110 nm, the shorter VLP's generally having the greater width (Fig. 1).

The Fine Structure of the Sheath of Volvox Carteri f. Weismannia

1977 ◽  
Vol 35 ◽  
pp. 346-347
Author(s):  
Regina Birchem
Keyword(s):  
Developmental Stages ◽  
Ruthenium Red ◽  
Sulfated Polysaccharides ◽  
Volvox Carteri ◽  
High Voltage Electron Microscopy ◽  
Ultrastructural Studies ◽  
Voltage Electron ◽  
Sheath Formation ◽  
And Inversion ◽  
Sheath Material

Spheroids of the green colonial alga Volvox consist of biflagellate Chlamydomonad-like cells embedded in a transparent sheath. The sheath, important as a substance through which metabolic materials, light, and the sexual inducer must pass to and from the cells, has been shown to have an ordered structure (1,2). It is composed of both protein and carbohydrate (3); studies of V. rousseletii indicate an outside layer of sulfated polysaccharides (4).Ultrastructural studies of the sheath material in developmental stages of V. carteri f. weismannia were undertaken employing variations in the standard fixation procedure, ruthenium red, diaminobenzidine, and high voltage electron microscopy. Sheath formation begins after the completion of cell division and inversion of the daughter spheroids. Golgi, rough ER, and plasma membrane are actively involved in phases of sheath synthesis (Fig. 1). Six layers of ultrastructurally differentiated sheath material have been identified.

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