Spruce Bog Research Articles

Repeated Permafrost Formation and Degradation in Boreal Peatland Ecosystems in Relation to Climate Extremes, Fire, Ecological Shifts, and a Geomorphic Legacy

Permafrost formation and degradation creates a highly patchy mosaic of boreal peatland ecosystems in Alaska driven by climate, fire, and ecological changes. To assess the biophysical factors affecting permafrost dynamics, we monitored permafrost and ecological conditions in central Alaska from 2005 to 2021 by measuring weather, land cover, topography, thaw depths, hydrology, soil properties, soil thermal regimes, and vegetation cover between burned (1990 fire) and unburned terrain. Climate data show large variations among years with occasional, extremely warm–wet summers and cold–snowless winters that affect permafrost stability. Microtopography and thaw depth surveys revealed both permafrost degradation and aggradation. Thaw depths were deeper in post-fire scrub compared to unburned black spruce and increased moderately during the last year, but analysis of historical imagery (1954–2019) revealed no increase in thermokarst rates due to fire. Recent permafrost formation was observed in older bogs due to an extremely cold–snowless winter in 2007. Soil sampling found peat extended to depths of 1.5–2.8 m with basal radiocarbon dates of ~5–7 ka bp, newly accumulating post-thermokarst peat, and evidence of repeated episodes of permafrost formation and degradation. Soil surface temperatures in post-fire scrub bogs were ~1 °C warmer than in undisturbed black spruce bogs, and thermokarst bogs and lakes were 3–5 °C warmer than black spruce bogs. Vegetation showed modest change after fire and large transformations after thermokarst. We conclude that extreme seasonal weather, ecological succession, fire, and a legacy of earlier geomorphic processes all affect the repeated formation and degradation of permafrost, and thus create a highly patchy mosaic of ecotypes resulting from widely varying ecological trajectories within boreal peatland ecosystems.

Small mammal dynamics in snow-covered forests

AbstractIn seasonal environments, the winter months can drive the structure and dynamics of vertebrate communities. Most ecological studies have focused on species above the snow, overlooking those within the subnivium (below-snow environment). The Great Lakes region of North America is characterized by seasonal snow cover and a diverse assemblage of small mammals, both of which are changing rapidly in response to a changing climate. To study the seasonal dynamics of small mammals, we sampled communities in three forest types (hardwood, hemlock-cedar, and spruce bog) in summer and winter over 2 years. We hypothesized that seasonal differences in communities would be moderated by forest structure in summer and snow in winter. We assessed community dominance via species diversity and the abundances of deer mice (Peromyscus maniculatus), white-footed mice (P. leucopus), and southern red-backed voles (Myodes gapperi). We estimated a Community Temperature Index (CTI; a metric of the balance between warm- and cold-adapted species in a community) and tested seasonal drivers of CTI. Species diversity was highest in spruce bogs in winter due to increased species evenness, but diversity was consistent year-round in hardwood and hemlock-cedar forests due to unchanging species dominance. Spruce bogs supported the coldest CTI in summer, but CTIs converged across forest types in winter. In summer, forest structure drove CTI; in winter, colder CTIs were associated with deeper snow and a warmer subnivium. Our work reveals that snow is a critical habitat and filter for cold-adapted species that ultimately structures small mammal communities. Given rapid changes in snow conditions due to climate change, we predict continued range contractions for subnivium-adapted species.

Pinus mugo shrubs on peat bogs in the Tatra National Park

Pinus mugo shrubs on peat bogs in the Tatra National Park (TNP) were for the first time described as a separated plant association by Obidowicz (1975) from only two mires. Since then, there have been no studies on peat bogs in the TNP and they have not been mentioned in the list of vegetation types of the Park. The research regarding the dwarf pine shrubs on mires in the Tatra Mountains was carried out in 2019. We mapped all patches of such vegetation (total – ~2 ha) on which we made 26 relevés. P. mugo shrubs on peat bogs occur within the complex of mire habitats, such as Norway spruce bog woodlands, raised bogs and poor fens. The shrub layer is dominated by Pinus mugo with admixture of dwarfish Picea abies. Typical plants of the herb layer are Vaccinium myrtillus, V. vitis-idaea, Eriophorum vaginatum and Oxycoccus palustris, whereas the most common mosses are Sphagnum magellanicum, S. capillifolium, S. russowi, Pleurozium schreberi. P. mugo shrubs on peat bogs in the TNP belong to the association Sphagno magellanici-Pinetum mugo.

Early response of ground layer plant communities to wildfire and harvesting disturbance in forested peatland ecosystems in northern Minnesota, USA

A rare, stand-replacing fire in northern Minnesota, USA provided the opportunity to compare the effects of wildfire and timber harvesting in two peatland forest communities, nutrient-poor black spruce (Picea mariana) bogs (BSB) and nutrient-rich tamarack (Larix laricina) swamps (RTS). We found the response between the two communities and their corresponding vegetation to be highly sensitive to different types and severity of disturbance, ranging from modest shifts in ground layer vascular plants and bryophyte species abundance, to wholesale plant community transformation resulting from the removal of the upper peat surface. Fire had a positive influence on black spruce regeneration within BSB sites, particularly areas experiencing lower levels of fire severity, with seedling densities significantly higher than harvest and control areas. Our results also suggest that ecosystem recovery will be rapid after low-severity fire in these areas, given that localized areas of peat combustion created suitable microsites for black spruce seedling establishment ensuring this species will remain a component of the post-fire communities. In contrast, tamarack regeneration was only documented in harvested RTS sites. For BSB, there was spatial heterogeneity in peat consumption as a result of fire behavior interacting with varying moisture conditions throughout peat hummocks and hollows. Light to moderate burning created suitable black spruce seedbeds by reducing cover of Sphagnum moss and the dominant ericaceous shrub Rhododendron groenlandicum, and increasing the cover of pioneering mosses, such as Polytrichum strictum. In RTS sites, fire typically consumed the entire upper peat surface, resulting in homogenization of community composition and retrogression towards marsh-like conditions dominated by cattails (Typha spp.). These findings underscore the importance of accounting for post-fire microsite heterogeneity when developing silvicultural systems for emulating natural disturbance processes in conifer forests with a naturally accumulated surface peat layer. In addition, the state shifts observed in areas experiencing high severity fire suggest that increases in fire frequency and severity may create significant challenges to maintaining forested conditions in these areas, particularly in RTS.

Gaseous mercury fluxes in peatlands and the potential influence of climate change

Climate change has the potential to significantly impact the stability of large stocks of mercury (Hg) stored in peatland systems due to increasing temperatures, altered water table regimes and subsequent shifts in vascular plant communities. However, the Hg exchange dynamics between the atmosphere and peatlands are not well understood. At the PEATcosm Mesocosm Facility in Houghton, Michigan, total gaseous Hg (TGM) fluxes were monitored in a subset of 1-m3 peat monoliths with altered water table positions (high and low) and vascular plant functional groups (sedge only, Ericaceae only or unmanipulated control) above the Sphagnum moss layer. At the SPRUCE bog in north-central Minnesota, TGM fluxes were measured from plots subjected to deep peat soil warming (up to +9 °C above ambient at a depth of 2 m). At PEATcosm, the strongest depositional trend was observed with the Low WT – sedge only treatment mesocosms with a mean TGM flux of −73.7 ± 6.3 ng m−2 d−1, likely due to shuttling of Hg to the peat at depth by aerenchymous tissues. The highest total leaf surface and tissue Hg concentrations were observed with the Ericaceae shrubs. A negative correlation between TGM flux and Ericaceae total leaf surface area suggests an influence of shrubs in controlling Hg exchange through stomatal uptake, surface sorption and potentially, peat shading. Surface peat total Hg concentrations are highest in treatments with greatest deposition suggesting deposition controls Hg accumulation in surface peat. Fluxes in the SPRUCE plots ranged from −45.9 ± 93.8 ng m−2 d−1 prior to the implementation of the deep warming treatments to −1.41 ± 27.1 ng m−2 d−1 once warming targets were achieved at depth and +10.2 ± 44.6 ng m−2 d−1 following prolonged deep soil warming. While these intervals did not differ significantly, a significant positive increase in the slope of the regression between flux and surface temperature was observed across the pre-treatment and warming periods. Shifts in vascular vegetation cover and peat warming as a result of climate change may significantly affect the dynamics of TGM fluxes between peatlands and the atmosphere.

Trapped Greenhouse Gases in the Permafrost Active Layer: Preliminary Results for Methane Peaks in Vertical Profiles of Frozen Alaskan Soil Cores

Degradation of organic carbon stored in permafrost may represent an additional source of atmospheric greenhouse gases (GHGs) in a warming climate. However, there is no clear understanding of how seasonal freeze–thaw affects gas permeability and emission of methane in permafrost soils, in part due to the lack of chemical and physical characterisation of the soils. Here, we report vertical profiles of CO2, CH4 and other soil properties with resolutions of 0.05–0.1 m depth from five soil cores, drilled to 0.9 m depth, in Alaskan permafrost during the early spring of 2013, when the ground was frozen under snow cover. Two cores from tundra and black spruce bog showed sudden increases in methane concentration (up to 416 µmol litre−1soil), indicating excess CH4 trapped in gas-impermeable soil layers during the freezing period. Active-layer cooling in late autumn, producing a frozen surface and relatively warm sub-surface, may have allowed underground microbial activity and facilitated CH4 production, while the upward transport of CH4 was hampered by the frost. Our preliminary results show that estimating annual GHG efflux from permafrost regions can be complicated because of heterogeneous distributions of trapped methane within soil columns. Copyright © 2016 John Wiley & Sons, Ltd.

Invasion of Raised Bogs by the Scots Pine; a Review of Vegetation History and Case Study in Selected Peat-Bogs in Bieszczady Mts. (Eastern Carpathians)

ABSTRACT The objective of this study was to analyse the diversity of pine and spruce bog forests on the domes of Carpathian raised bogs located in the Upper San River Valley. In order to determine the present species composition, 59 phytosociological releves were performed (32 within spruce forests, and 27 in pine forests). For all releves, the Shannon-Wiener index, evenness index and mean Ellenberg indicator values were calculated. Detrended correspondence analysis was conducted in order to determine the degree of similarity between distinct units of vegetation and to identify the main environmental gradients that have an impact on species composition. The results revealed considerable similarities between the ground vegetation of both spruce and pine forests growing on peat substrate. Within pine forests there was a greater proportion of certain plant species characteristic of raised bogs, and plants typical of bog coniferous forests. The ground flora of spruce forests was more diverse. Although spruce ...

Fuel load, structure, and potential fire behaviour in black spruce bogs

Boreal peatlands in Canada comprise a substantial store of soil organic carbon (peat), and this peat is vulnerable to extensive burning during periods of extended drying. Increased frequency of extreme weather events in boreal regions is expected with future climate change, and the conditions that would support sustained smouldering peat combustion within peatlands may be more common. Organic soils tend to burn by smouldering combustion, a very slow-moving process in fuels such as those found in peatlands. Thus the most extreme conditions for carbon loss to the atmosphere due to the burning of peat likely occur when widespread propagation of flaming combustion leads to widespread initiation of smouldering. To investigate the potential for large-scale, high-intensity fire spread across forested bogs, we examined the fuel conditions in forested bogs necessary to support active crown fire. We measured surface and canopy fine fuels (those available to contribute to the propagating energy flux of the main flaming front) across a postfire chronosequence of forested boreal bog from central Alberta, Canada. We found that fuel load of fine surface material remained relatively constant across the chronosequence and at levels large enough to support crown fire initiation. Black spruce (Picea mariana (Mill.) B.S.P.) regeneration begins to fill in the crown space with increasing time since disturbance and achieves crown bulk densities similar to black spruce upland forests. We estimated that after about 80 years, the black spruce canopy has developed enough available fuel to support active crown fire on between 10% to 40% of days in a typical fire season in central Alberta, Canada. Broad-scale propagation of high-intensity fire across a peatland when coincident with drought-induced lower moisture in deep peatland layers has the potential to lead to a substantial release of stored terrestrial carbon.

Wildfire Consumption and Interannual Impacts by Land Cover in Alaskan Boreal Forest

AbstractBoreal forest fires are an important source of terrestrial carbon emissions, particularly during years of widespread wildfires. Most carbon emission models parameterize wildfire impacts and carbon flux to area burned by fires, therein making the assumption that fires consume a spatiotemporally homogeneous landscape composed of predominantly spruce forests and peat bogs with deep duff layers. While recent efforts have demonstrated that boreal forest fires heterogeneously consume aboveground vegetation, little remains known about the vegetation consumed during such fires. We examined climate, land cover, area burned, and fire impacts for large fires (2002 to 2009) across the Alaskan boreal landscape to address the validity of assumptions made by carbon emissions models for boreal fires. Results indicated that while coniferous vegetation, particularly spruce forests and spruce bogs, comprised the majority of the area burned in all years, shrub land cover comprised a substantial proportion (up to 35 %) of the area burned during warmer years of the study period. Interannual climate variability significantly influenced both the proportion of vegetation classes burned and the distribution of fire impacts across years and vegetation classes. We found that surface fuel modifications were sensitive to both the vegetation type that burned and climatic conditions. Area burned is an inadequate input metric for increasingly refined carbon emissions models, and consideration of heterogeneous fire impacts may improve carbon emissions modeling.

Radionuclides in the terrestrial ecosystem near a Canadian uranium mill--Part I: Distribution and doses.

Soils, vegetation, small mammals, and birds were measured for uranium series radionuclides at three sites near the operating Key Lake uranium mill in northern Saskatchewan. Sites, impacted by windblown tailings and mill dust, had significantly higher concentrations of uranium, 226Ra, 210Pb, and 210Po in soils, litter, vegetation, tree needles and twigs, small mammals, and birds, compared to a control site. Samples were collected from both upland jackpine and black spruce bog habitats in triplicate at each site. Both habitats were similar in radionuclide accumulation. Absorbed doses averaged 0.92, 8.4, and 4.9 mGy y(-1) to small mammals and 2.0, 5.8, and 2.8 mGy y(-1) to Lincoln's sparrows at the control, tailings, and mill sites, respectively. These doses do not include doses from short-lived radon progeny. The majority of the dose increment at the tailings and mill sites was due to 226Ra, whereas it was 210Po at the control site. Thus, use of a radiation weighting factor of 20 for alpha radiation raised equivalent doses (in mSv y(-1)) by nearly a factor of 20.

Radar detection of flooding beneath the forest canopy: a review

Synthetic aperture radar remote sensing is a promising tool for detection of flooding on forested floodplains. The brigtht appearance of flooded forests on radar images results from double-bounce reflections between smooth water surfaces and tree trunks or branches. Enhanced backscattering at L-band has been shown to occur in a wide variety of forest types, including cypress-tupelo swamps, temperate bottomland hardwoods, spruce bogs, mangroves and tropical floodplain forests. Lack of enhancement is a function of both stand density and branching structure. According to models and measurements, the magnitude of the enhancement is about 3 to 10 dB. Steep incidence angles (20-30 deg) are optimal for detection of flooding, since some forest types exhibit bright returns only at steeper angles. P-band should prove useful for floodwater mapping in dense stands, and multifrequency polarimetric analysis should allow flooded forests to be distinguished from marshes.

Bioconcentration of fallout 137Cs by fungi and red-backed voles (Clethrionomys gapperi).

Cesium-137 and 40K concentrations were measured in vegetation and in red-backed voles (Clethrionomys gapperi) in southeastern Manitoba, Canada, following the Chernobyl accident in 1986. Voles from wet coniferous habitats contained concentrations of 137Cs twenty- to fiftyfold higher than voles from deciduous habitats. Maximum 137Cs values were observed in autumn. Voles captured in a spruce bog at this time contained an average body burden of about 11 Bq. Concentrations in vegetation samples were similar to those found by other researchers. Overall, there was only minimal evidence of contamination attributable to Chernobyl in either vegetation or voles. The primary source of 137Cs in voles appeared to be dietary, particularly mushrooms that contained up to 74 Bq g-1 ash. Based on physiological constraints, mushrooms were the only plausible source of 137Cs in autumn diets. Elevated values at other times in coniferous areas may have been related to the consumption of epiphytic lichens. These findings suggest that fungi, or the animals that consume them, can serve as sensitive indicators of 137Cs contamination in the environment.

Impact of Demographic Parameters upon a Population of Spruce Grouse in New Brunswick

Densities, age ratios, survival rates, production, dispersal rates (in autumn), and recruitment rates are documented for spruce grouse (Dendragapus canadensis) at Sevogle, New Brunswick, during 1976-83. These data were used to predict the relative impact that each parameter had upon grouse density in the breeding period. This approach indicated that population size of spruce grouse was not controlled by the effects of a single parameter. Density of immigrants, the rate at which they were recruited, and the rate at which locally produced juveniles were recruited were predicted as the most important to population change. Their effects, however, did not in all cases exceed the impact from density of residents the previous year and their survival to the next year. J. WILDL. MANAGE. 51(4):771-777 Life history traits are strongly influenced by spatial and temporal variation in at least certain environmental factors, and variations in life history traits are equally important to their evolution, as are mean values (Stearns 1976:37). This should be true particularly for species occupying varied habitats over a broad geographical area. Spruce grouse are distributed across coniferous and mixed-wood boreal forests of North America, typically at low densities although Szuba and Bendell (1983) document exceptions. Population data have accumulated, but we do not yet understand the meaning of spatial differences that occur in demography and certain life history traits. Substantial differences in production and mortality of spruce grouse occur among different forest types at different latitudes across the range of the species (Ellison 1974; Keppie 1979, 1982); demography in New Brunswick appears closer to that in Alaska than for the Franklin's race (D. c. franklinii) in Alberta. A comparative approach will help form generalities about life history. The purpose of this paper is, 1st, to document demographic characteristics of spruce grouse at 1 locality in New Brunswick and to make selected comparisons with grouse at Gorge Creek, Alberta. Second, from these data I estimate the relative impact that each parameter had upon changes in population density. Many authors note variation in 1 or more demographic rates but do not balance them against each other and changes in population (Bendell 1972:81). That failure still is prevalent, especially if key factor analyses on mortality (e.g., Watson [1971], Weeden and Theberge [1972]) are inappropriate (Kitching 1976, Krebs 1978:2465). Present analyses document the potential influence that production, mortality, and dispersal processes have upon population size and predict that several act simultaneously to control grouse density. I especially thank the 10 persons that have worked in the field with me, 1976-83. I thank F. C. Zwickel and R. A. Lewis for review of preliminary analyses and their cautions about sample sizes and generality. I appreciate reviews by A. Boer and J. Towers. Field studies were supported by the Nat. Sci. and Eng. Res. Counc. Can. and the Univ. New Brunswick. STUDY AREA AND METHODS Spruce grouse were studied at Sevogle in northeast New Brunswick (46N, 660W), Canada, from 1976 to 1983, excepting 1981. Fieldwork was conducted in 2 areas, SNW and WB, 1.5 km apart and separated by the Big Sevogle River. Logistic problems prevented both forest tracts from being worked each year with equal intensity. A mosaic of different stands occurs at Sevogle, principally dense black (Picea mariana) and red (P. rubra) spruce-balsam fir (Abies balsamea); lightly stocked black spruce-jack pine (Pinus banksiana) (Redmond 1982:fig la); dense, young jack pine (Redmond 1982:fig. ib); fully stocked mature jack pine, all principally dry upland sites; and white cedar (Thuja occidentalis)-spruce bogs. Intolerant hardwoods, such as white birch (Betula papyrifera) and red maple (Acer rubrum), occur on wet sites. The Sevogle area is surrounded by extensive softwood forest, principally spruce-fir, typical of that in the east, and which is occupied by grouse. Field methods were similar to those used earlier in southwest Alberta (Keppie 1979), with 2-

DEUX NOUVELLES FOURMIS NÉARCTIQUES: LEPTOTHORAX RETRACTUS ET L. SPHAGNICOLUS (FORMICIDAE, HYMENOPTERA)

RésuméTwo new Nearctic ants of the genus Leptothorax (sensu stricto) are described. One, L. retractus, has a transcontinental range, while the other, L. sphagnicolus, was found until now only in the spruce bogs of the Saguenay–Lac-St-Jean region in Quebec. Their chromosome numbers are, respectively, n = 17–18 and n = 13. Both species exhibit an unusual production of intermorphic females and a boreo-temperate geographic distribution. Available bio-ecological data and their taxonomic position within the genus are discussed.

An Identification of Environmental Disturbances from Road Developments in Subarctic Muskeg

The location, nature, and magnitude of some environmental changes associated with the introduction of a road across a muskeg in the discontinuous permafrost zone are identified from examination of near-infrared Landsat images. Impedance of natural surface drainage by the presence of a roadbed is hypothesized to transmit upstream hydro-thermal changes through the muskeg terrain, which in turn cause change in the muskeg vegetation community. Differences among the near-infrared spectral reflectances of fen, black spruce bog, and Sphagnum bog communities are found sufficiently large for use as indices of differences in the actual biophysical natures of the muskegs. Key words: environmental impact, northern Canada, muskegs, hydrology, Landsat interpretation, permafrost, road design

Lichen Decomposition in a Black Spruce Bog

AbstractNylon mesh litter bags containing Parmelia caperata, P. flaventior, P. subrudecta, Evernia nesomorpha, Hypogymnia physodes and Umbilicaria muehlenbergii were placed on the floor of a black spruce bog in northern Minnesota to study the rates of decomposition. P. caperata and E. mesomorpha had decomposed after 10 months. Most of the lichens had completely decayed after 13 months but a few thalli of some species placed on top of hummocks were still alive. The species with usnic acid decayed as rapidly as those without. Lichens decompose rapidly but not more rapidly than some vascular plants.

Productivity of the antFormica dakotensis in a spruce bog. 2. Annual variations in colony density, nest inhabitation and spatial distribution

Apres quatre ans de production, la densite deFormica dakotensis affiche une moyenne de 172,2 colonies par hectare, dans la pessiere tourbeuse de Saint-Ambroise, Quebec. Avec un coefficient de variation de 2% seulement, la population des colonies apparait en equilibre avec le milieu. Une telle stabilite cache toutefois des fluctuations internes qui se traduisent par un taux effectif de renouvellement annuel des colonies de 18,7%, a la fin d'une saison de croissance, alors que le taux specifique de renouvellement annuel de la population de colonies pendant le temps d'observation s'eleve a 23,6%. Cette derniere valeur est comparec a celles obtenues pour d'autres especes deFormica. Le taux moyen de naissance des colonies s'eleve a 22,9% et celui de mortalite a 23,5%. La longevite potentielle d'une colonie est estimee a partir des donnees sur l'occupation continue des nids recenses en 1972. La reoccupation de nids abandonnes se revele d'autant plus grande que ceux-ci sont jeunes, c'est-a-dire en bon etat. D'autres especes de fourmi utilisent parfois les nids construits et abandonnes parF. dakotensis. Il existe un lot permanent de nids definitivement abandonnes qui entrent alors en decomposition, puis disparaissent. La repartition spatiale demeure au hasard avec une faible tendance vers le type contagieux. Les colonies se concentrent dans un habitat particulier du biotope. L'evolution de ce dernier influence l'avenir de la population de colonies et sa densite. Les dimensions des nouveaux nids sont analysees en fonction de leur occupation. Le comportement de construction de cette fourmi illustrerait une etape initiale dans l'apparition du polycalisme chez le genreFormica.

Peat Temperature Regime of a Minnesota Bog and the Effect of Canopy Removal

Peat bogs occupy approximately 6 000 000 ha in the cool sub-humid northern Lake States of the U.S.A. These peatlands are intimately associated with the regional water resources, often serving as the source of streamfiow. They also represent unique wetland ecosystems. Temperature is an important characteristic both of the bog environment and the quality of streamflow water. Alteration of peat temperature could result in changes in the surface vegetation and changes in microbial activity, so affecting the amount of organic matter accumulated (Clymo 1965; Lather & Cragg 1967; Moore & Bellamy 1974) and the quality of streamfiow water. Therefore, it is necessary to determine the temperature regimes of peat bogs in both undisturbed and disturbed situations prior to any large-scale alterations of management and energy input. Accordingly, temperature regimes were determined in a strip-cut black spruce bog to evaluate the effect of canopy removal. METHODS The study bog, located in northern Minnesota on the Marcell Experimental Forest (c. 47032'N, 93028'W), is approximately 560 m long and 140 m wide with the long axis oriented north and south. The peat profile of this lake-filled, forested bog has been described by Boelter (1964). The bog is isolated from the regional groundwater system. Precipitation and run-off from the adjacent uplands comprise the water input to the bog. Outflow is primarily as intermittent surface streamflow from the south end of the bog. In the winter of 1968-69, 30-m-wide strips were clear-cut, in an east-west direction, leaving 45-m-wide strips of sixty-two-year-old black spruce (Picea mariana (Mill.) B.S.P.). The crown closure of the forested strips was& approximately 7500. The strips were logged when snow cover was ample, so that disturbance of the surface vegetation was negligible, and a luxuriant sedge cover rapidly established in the following summer (Brown 1972). Eight temperature stations were located at the south end of the bog and eight at the north end. Two stations were located in the centre of clear-cut strips, two were in the centre of the forested strips and four were on the boundaries between strips. Peat depth at the temperature stations ranged from 2 to 2-8 m. Each temperature station consisted of a series of copper-constantan thermocouples, located at depths of 0-025, 0 3, 1 and 2 m below the interface of the living sphagnum moss and the organic soil material. The thermocouples were inserted through a wooden stake 2-5 x 2-5 cm and 2 m long; the stake was pushed into the peat to the desired depth. Air temperatures were measured at two locations in the clear-cut strips and two locations in the non-cut strips by shaded thermocouples 1 m above the bog surface. Temperatures were read with a portable potentiometer. A battery-operated resistance heating unit was

Water Level Fluctuation in a Northeastern Ontario Peatland

Depths to water level and changes due to local climate were dissimilar in five peatland conditions in northeastern Ontario. The deepest water level and the greatest fluctuations occurred in an ombrotrophic black spruce bog site. The sedge-dominated poor fen site was submerged following every heavy rain. Waterlogged conditions remained within 6 cm of the surface at all times because of the influence by the water level of Dai Lake. The water level of Dai Lake varied within a narrow range because the loss of water was primarily dependent on slow seepage and evaporation. The lagg site was affected by continuous inflow, high water levels, and fast run-off, therefore, a larger fluctuation of water level prevailed at this site.

Studies on the Bryophytes of Southern Manitoba. VII. Distribution of Terrestrial Bryophytes in a Black Spruce Bog in Bird's Hill Provincial Park

The seventeen most common terricolous bryophytes in calcareous black spruce bog forest occur in three distinct groups occupying different microtopographic sites. The chief factors governing the distribution of these groups are moisture availability, shade, and competition. There have been few attempts to study in detail the ecology of terrestrial bryophytes in coniferous bog forests. Even the studies of Bevis (1960), Jeglum (1971), Reichle and Doyle (1965), and Sjors (1961) have little quantitative information relating bryophyte species to microsite factors, although in other respects they provide much useful data on the bryophytes of bog forests and bogs. Bevis (1960) used transects in his phytosociological study on bogs and bog forests, but his rather large sampling units (2 X 2 m quadrats) were not intended to sample the mosaic of microsites. According to Kil'dyushevskii (1964), a study of the distribution of species in the immediate soil cover with respect to the elements of the microrelief can reveal much concerning the biology and ecology of these species. With this observation in mind, we undertook this study in an attempt to elucidate the microtopographic distribution of bryophytes in hummocky black spruce bog forest, and to find how microenvironmental factors might account for these distribution patterns. The site chosen was in Bird's Hill Provincial Park, an area of coniferous and mixedwood forest some 36 hectares in extent approximately 25 km northeast of downtown Winnipeg. The park lies in the transition zone between the Aspen-Oak and Manitoba Lowlands sections of the Boreal Forest Region (Rowe, 1959). On Bird's Hill itself, white spruce (Picea glauca) with some jack pine (Pinus banksiana) are associates of the dominant oak (Quercus macrocarpa) and aspen (Populus tremuloides). However, most of the coniferous forest is in wet, poorly drained areas, where bog forests of black spruce (Picea mariana) and tamarack (Larix laricina) have developed, usually on deep layers of peat. We will report in separate publication other aspects of our work on the bryophytes of the park, which have not previously been studied.