Bog Forest Research Articles

Vegetation change in a South German raised bog: Ecosystem engineering by plant species, vegetation switch or ecosystem level feedback mechanisms?

The main results of a long-term ecological study from 1957 to 1994 are presented. Aspects of vegetation dynamics and hydrology of a South German ombrogenous bog were analysed in different spatial scales and temporal periods. Vegetation change from 1957 to 1992 was documented by Permanent plots and comparison of vegetation maps. Pinus sylvestris dominated forest stages, bog forests and Calluna vulgaris hummocks increased by replacing Sphagnum lawns and hollow structures in the course of succession. Fundamental changes in hydrology occurred in the same period of time. Monthly water level means dropped by approximately 10–15 cm and duration and extent of the maximum water levels were reduced. Discharge of the catchment area remained almost constant during the winter months, but summer discharge significantly declined. Important climatic factors (air temperature, monthly and annual precipitation) showed a common high variability during the same period, but no significant trend could be found. At the same time, trend analysis indicates a 350 mm increase in the total yearly evapotranspiration. Numerous interdependences between vegetation development and hydrology are hidden behind the long-term dynamics of this ecosystem. The complexity of the bog ecosystem prevents a simplistic separation of causes and effects. But this long-term study can help to clarify the debate about the effectiveness of vegetation switches or species acting as ecosystem engineers. The invasion of tree species of the genus Pinus and Betula contributes to structure important hydrologic features that change abiotic conditions for other species within the ecosystems. However, such processes of interaction between biotic and abiotic ecosystem properties cause additional positive or negative feedback mechanisms. Succession in raised bogs might be a good way of showing that discrimination between biotic and abiotic ecosystem processes requires an interdisciplinary approach.

Hydro-ecological analysis of a sacred lake watershed system in relation to land-use/cover change from Sikkim Himalaya

The hydrology and ecological linkages between Khecheopalri lake and its surrounding watershed (area: 12 km 2) in Sikkim were investigated to assess the long-term impacts of land-use/cover change on the hydrology of the lake ecosystem and bog formation around the glaciated lake. Significant land-use/cover change occurred in the past 4 decades. The bog area expanded by 67%, while the area under agriculture land in the lake watershed grew by 63% between 1988 and 1997. Overland flow was highest on the bare land (4.77% of the precipitation) and lowest in areas of cardamom-based agroforestry (1.79%). Soil and nutrient losses were highest in the cultivated area and least in the cardamom agroforestry system. Sediment loads of 345 Mg year −1 were recorded at the lake inlet and of 316 Mg year −1 at the outlet. Annual soil loss from the lake watershed was 502 Mg km −2 and a net sediment deposition in the lake was 141 Mg year −1. The lake received high nutrient loads (organic carbon of 10.2 Mg year −1, total nitrogen of 1.01 Mg year −1 and total phosphorus of 0.51 Mg year −1) from soil erosion and overland flow. The pH, total phosphorus and bulk density of the peat increased from the lake towards the bog-forest edge. This reflects the trapping of sediments and nutrients around the bog forest margin, although their retention is limited. Agricultural practices should be minimized in the upper part of the watershed and agroforestry practices should be encouraged to maintain the health and longevity of the lake.

Runoff generation in a hypermaritime bog-forest upland

Shallow hillslope groundwater is shown to be a dominant source of streamflow in sloping bog–forest uplands of the North Coast Forest District, British Columbia, based on a three-component isotope hydrograph-separation analysis conducted in July 1998. At peak discharge during a mid-summer rainfall event, new water contributions accounted for only 12% of streamflow, whereas shallow groundwater accounted for 85% of streamflow and bog groundwater and deep hillslope groundwater accounted for the remaining 3% of streamflow. Mean residence time of water is estimated to be about 2 months, and soil storage capacity is roughly 400 mm based on the analysis of the baseflow discharge and isotopic response. Systematic seasonal shifts in deuterium excess of rainfall in the Prince Rupert area are shown to be useful for labelling shallow and deep groundwaters based on their residence time signatures. The potential for using dissolved organic carbon and deuterium excess as hydrological tracers is also discussed. Copyright © 2000 John Wiley & Sons, Ltd.

Winter CO2, CH4 and N2O fluxes on some natural and drained boreal peatlands

CO2 and CH4 fluxes during the winter were measured at natural and drained bog and fen sites in eastern Finland using both the closed chamber method and calculations of gas diffusion along a concentration gradient through the snowpack. The snow diffusion results were compared with those obtained by chamber, but the winter flux estimates were derived from chamber data only. CH4 emissions from a poor bog were lower than those from an oligotrophic fen, while both CO2 and CH4 fluxes were higher in the Carex rostrata-occupied marginal (lagg) area of the fen than in the slightly less fertile centre. Average estimated winter CO2-C losses from virgin and drained forested peatlands were 41 and 68 g CO2-C m- 2, respectively, accounting for 23 and 21% of the annual total CO2 release from the peat. The mean release of CH4-C was 1.0 g in natural bogs and 3.4 g m-2 in fens, giving rise to winter emissions averaging to 22% of the annual emission from the bogs and 10% of that from the fens. These wintertime carbon gas losses in Finnish natural peatlands were even greater than reported average long-term annual C accumulation values (less than 25 g C m-2). The narrow range of 10–30% of the proportion of winter CO2 and CH4 emissions from annual emissions found in Finnish peatlands suggest that a wider generalization in the boreal zone is possible. Drained forested bogs emitted 0.3 g CH4-C m-2 on the average, while the effectively drained fens consumed an average of 0.01 g CH4-C m- 2. Reason for the low CH4 efflux or net oxidation in drained peatlands probably lies in low substrate supply and thus low CH4 production in the anoxic deep peat layers. N2O release from a fertilized grassland site in November–May was 0.7 g N2O m-2, accounting for 38% of the total annual emission, while a forested bog released none and two efficiently drained forested fens 0.09 (28% of annual release) and 0.04 g N2O m- 2 (27%) during the winter, respectively.

Ecosystem types of boreal forest in the North Klondike River Valley, Yukon Territory, Canada, and their productivity potentials

Vegetation, environmental characteristics, and forest productivity were studied in the boreal forest in the North Klondike River Valley, Yukon Territory, Canada. The concept and approach of biogeoclimatic ecosystem classification were followed. For the treed vegetation, five ecosystem types were distinguished based on vegetation structure and physical and chemical properties of soils. They were: 1) spruce-lichen type, 2) spruce-moss type, 3) spruce-Equisetum type, 4) spruce-willow type, and 5) bog forest type. These types were differentiated mainly by moisture regime and base status of soils. The sequence of the ecosystem types reflected their topographical position from slope summit to valley bottom. The spruce-lichen type developed in the driest and nutritionally impoverished habitats, the spruce-Equisetum type occurred in moist and nutritionally enriched sites, and the spruce-moss type was found in between them. The bog forest type occurred where peat had accumulated sufficiently to generate ombrotrophic conditions in habitats of high water table underlain with permafrost. The spruce-willow type developed along small creeks where substrates were very coarse. Tree growth characteristics were measured, except for the bog forest type that did not have trees over 5 m tall. Total volume of standing trees ranged from 29 to 582 m(3)/ha, with an overall mean of 216.9 m(3)/ha. The spruce-Equisetum type exhibited the highest figure, 413.5 m(3)/ha, while spruce-lichen type the lowest one, 87.7 m(3)/ha. Mean annual increment ranged from 0.15 to 2.66 m(3)/ha, with an overall mean of 1.10 m(3)/ha. A similar tendency was noted for all other forestry characteristics, i.e., the spruce-Equisetum type showed the highest productivity while the spruce-lichen type the lowest. This tendency was considered to be attributed to the availability of moisture and basic cations in soils.

Carbon trace gas fluxes along a successional gradient in the Hudson Bay lowland

Patterns and controls of carbon trace gas emissions from wetlands may vary depending upon the spatial and temporal scale being examined. The factors affecting these emissions are thought to be hierarchically related according to their respective scales of importance. A hierarchical model of processes controlling methane emissions from wetlands is presented and examined here. During the 1990 Northern Wetlands Study (NOWES) methane (CH4), carbon dioxide (CO2), and non‐methane hydrocarbon (NMHC) fluxes were measured in static chambers along a 100 km transect in the Hudson Bay lowland (HBL). Environmental variables, vegetation abundance, and ecosystem age and structure were also quantified at each sampling site. The findings indicate that CH4 emissions from peatlands (e.g., bogs and fens) and other wetlands (e.g., salt marshes) in the region were low, and were nil or negative (i.e., CH4 uptake) in forests and bog forests dominated by aspen and black spruce. Site to site variations in mean CH4 flux appeared to be most closely related to mean water table and sedge productivity, both of which are intercorrelated. Seasonal changes in CH4 flux tend to follow soil temperature fluctuations. Instantaneous CO2 and CH4 daytime fluxes exhibit a negative correlation, suggesting that photosynthetic assimilation of carbon may be related to CH4 emissions, although the processes of CO2 and CH4 production are occurring at somewhat different temporal scales. No diurnal variations in CH4 flux could be detected. While soil water pH trends are not fully explored, there is some indication that high CH4 fluxes are concentrated around pH 4 and pH 7. Soil temperature closely follows the seasonal progression of CH4 flux. Estimated CH4 seasonal flux (1.5–3.9 g CH4 m−2 season−1) and estimated aboveground net primary productivity (NPP) (90–400 g dry weight m−2 season−1) show systematic changes along a successional sequence which are consistent with patterns predicted from successional theory. Estimated seasonal NMHC emissions (0.5–1.4 g C m−2 season−1) exhibit an increase along the succession from salt marsh to Sphagnum bog communities. Data from several studies were combined to estimate seasonal CO2 flux from three sites. The estimated fluxes range from a net uptake of 23 g CO2 m−2 season−1 to a net loss of 77 g CO2 m−2 season−1, although there are large uncertainties in these estimates. It is inferred from the assessment of ecosystem age and structure that disturbance effects and successional changes occurring over hundreds to thousands of years in the HBL strongly control regional CH4, CO2 and NMHC emissions by influencing NPP, species composition, community structure, soil (peat) development, and landscape hydrology. Given this, it is likely that models of carbon trace gas flux based on succession models may be useful in predicting climate change‐landscape change feedbacks.

Relative Abundance of Herpetofauna among Eight Types of Maine Peatland Vegetation

Relative Abundance of Herpetofauna among Eight Types of Maine Peatland Vegetation

Evaluation of trace metal deposition history and potential element mobility in selected cores from peat and wetland ecosystems

Peat and wetland ecosystems serve as repositories for atmospheric chemicals from anthropogenic input and may complement the current studies of the deposition history using lake sediments. Using natural atmospheric tracers, studies of the mechanisms of chemical-matrix interactions and mathematical simulation models have been conducted to guide our evaluations of bog and wetland ecosystems. The deposition histories of Pb and other elements have been determined in 210Pb-dated cores from bogs and wetlands located in Virginia, Pennsylvania and New York. Two marshlands in the Hudson River, New York — Tivoli Bays and Stockport marsh — show the regional contaminant history of Pb emissions from coal burning, heavy industries and gasoline consumption from 1850 to the present. Accumulations increase from a background of 2 and 8 μg cm −2 year −1 to the present of about 12 and 25 μg cm −2 year −1, respectively. For comparison, at a bog near Oneonta, New York, Pb values prior to 1780 were 0.1 μg cm −2 year −1 and have increased to 3.3 μg cm −2 year −1. In a forest bog east of the industrial and coal mining region of Pittsburgh, PA, the Pb has increased from 4 μg cm −2 year −1 before 1820 to a maximum of 17 μg cm −2 year −1 in 1978. Similar increases in Pb deposition values over time of 10–20 times have been measured in eastern, midwestern and western U.S.A. lake core samples. After deposition on a bog or wetland, hydrological, chemical, and biological parameters can influence the migration of specific elements. Cesium-137 has limited mobility in organic-rich bogs, but is much less mobile in more minerotrophic bogs. An advective/dispersive transport code has been developed that explains the 137Cs mobility and may be used to predict other element mobilities.

Ecological and hydrological aspects of peat formation

Abstract Peat formation is dependent upon an imbalance in the energetic relations of an ecosystem such that the total energy fixation by photosynthesis exceeds the total respiration on the part of the plants, animal consumers, detritivores and microbial components of the ecosystem. The imbalance comes about through the impedence of some detritivore and microbial activity as a result of the waterlogging of the environment. A knowledge of hydrological relationships in different types of mire (any freshwater wetland ecosystem in which soil organic matter accumulates) is necessary for the understanding of the rate of formation and the nature of the peat formed. A hydrological scheme for mire classification is discussed in relation to the type of peat developed from the mire types described, particularly the proportion of inorganic material incorporated into various peatland types. Two major hydrological divisions can be distinguished—those depending entirely upon rainfall for their water intake and those receiving water both by rainfall and overland drainage. The differentiation is of profound importance in terms of the inorganic (loss on ignition; ash) content of the peat, since the rain-based (ombrotrophic) system generally has a far more limited supply of inorganic material than the flow-fed (rheotrophic) one. One must seek models for coal-forming systems among ombrogenous tropical mires. Elevated peat-forming surfaces equivalent to the temperate raised mires are recorded from tropical areas and some of these bear vegetation whose physiognomy (general form and structure) resembles that of reconstructed coal forests. In these bog forests, peats of low ash content accumulate and such mires may prove to be the closest modern analogy to coalforming systems.

Bogs as Beaver Habitat in North-Central Minnesota

In a 100-km2 area surveyed for beaver activity, one-third of the active colonies were in bogs and two-thirds were in lakes and rivers. From 1979 to 1981, the percent of colonies in bogs increased from 29% to 36%. Of 481 bogs in the study area, 200 (42%) had current or previous history of beaver activity (colony sites and work areas). At 101 bogs (21 %), dam construction in seepage zones created flowages. Most impoundments were built at minerotrophic sites. Moats were used at 99 bogs (21 %), where beavers preferred sedge-moss cover and avoided tall shrub and wooded cover. The results show that bogs are suitable habitat for beavers. INTRODUCTION The suitability of lake and stream habitat for beavers (Castor canadensis Kuhl.) has been well-studied (Retzer et al., 1956; Northcott, 1964, Tufts, 1967). Although beavers frequently colonize lakes and streams that are adjacent to bog areas, few researchers have mentioned that beavers are capable of colonizing bogs that lack open water. Northcott (1964) reported a single instance of a colony in a closed bog, but reference by others to similar phenomena has been anecdotal (Schwintzer and Williams, 1974; Buell and Buell, 1975; Worley, 1981). Marshall and Miguelle (1978) in their review of wildlife on Minnesota peatlands mentioned only that beavers colonize bogs that have existing open water. Although there are few accounts of beavers colonizing bogs, colonies in bogs are locally common in N-central Minnesota, and in some areas they are more prevalent than in lakes or streams. Beavers are well-adapted to aquatic habitats, but their ability to create open water in closed bogs is an unusual situation that may involve specialized behavior. The purpose of this paper is to document the extent of bog use by beavers in a section of Cass Co., Minnesota, and to determine what biological and physical features of bogs are associated with use by beavers. METHODS AND PROCEDURE The 100-km2 study area, located E of Backus in Cass Co., included most of Deerfield Township (T139N R31W) and a few adjacent sections of Hiram, Bull Moose, Powers and Birch Lake townships. The topography is characterized by a rugged terminal moraine belt with ca. 250 small lakes and 500 bogs in depressions between hills. The upland forest is predominantly paper birch (Betula papyrifera) and trembling aspen (Populus trernuloides). I used aerial photographs to detect the 512 bogs larger than 0.12 ha in the study area. Bog areas adjacent to lakes and streams were not included unless the connection was minimal and the bog occupied a separate basin. In the field, 481 bogs were evaluated for the presence of beaver activity and classified according to predominant cover type as sedge-moss, tall shrub or wooded bog. Sedge-moss bogs were characterized by floating mats of sedges (Carex) and/or Spagnum moss and ericaceous shrubs covering most of the basin. Tall shrub bogs were dominated by alder (Alnus rugosa) (the brushy fen of Boelter and Verry, 1977), or by Betula pumila, Larix laricina and Picea mariana -the early seral stages of bog forest on ombrotrophic sites. Wooded bogs were dominated by L. laricina, P mariana and occasionally by trees from later stages. Most bogs in the study area were less than 3 ha and had either monotypic vegetation or predominant cover types that were easily recognizable. Aerial and ground surveys were used to detect both colony sites and work areas at 'Present address: Department of Botany, Louisiana State University, Baton Rouge 70803.

The Vegetation of Little Cedar Bog, Southeastern New York

LYNN, L. M. (Bergen Comm. Coll., Paramus, NJ 07652. The Vegetation of Little Cedar Bog, southeastern NY Bull. Torrey Bot. Club 111: 90-95. 1984.-The vegetation of a bog surrounding Little Cedar Pond in southeastern New York was quantified using phytosociological methods in a belt transect and quadrats established along two transects. The bog forest is a homogeneous stand of southern white cedar (Chamaecyparis thyoides). The bog mat is characterized by leatherleaf (Chamaedaphne calyculata) as the dominant bog shrub with significant amounts of sheep laurel (Kalmia angustifolia) and dangleberry (Gaylussacia frondosa).

Comparative community structure ofChamaecyparis thyoides bog forests: Canopy diversity

Chamaecyparisthyoides (L) BSP (Atlantic White Cedar), found only in acid wetlands of the eastern United States coast, dominates readily-recognized biotic assemblages that vary with latitude. This is the first of a four-part study of the literature on biota associated withC.thyoides throughout its range. The number of tree species found with cedar in each state ranges from 2 to 18. State regions with the highest canopy diversity are: east and west Florida, Massachusetts and Mississippi. States with the lowest number of associated tree species are: Alabama, Georgia and New York and Maryland. Fifty-five tree species are found growing withC.thyoides overall, with no single species in all the 17 state-regions of its range. Most trees co-occur in a narrow band: over 85% are found in 5 states or less. Species most frequently associated are:Acerrubrum,Nyssasylvatica andMagnoliavirginiana. Fire control, logging, road building, mosquito control and agricultural practices continue to alter and obliterateC.thyoides communities.

Vegetation of the Boreal Forests South of James Bay: Non‐Centered Component Analysis of the Vascular Flora

Results from an extensive vegetation survey of 1971 boreal forest stands, encompassing a full spectrum of succession and site types in the regions of Ontario and Quebec south of James Bay, are reported. Non—centered principal component analysis plus varimax rotation (nodal component analysis) is applied to overstory and understory data in order to detect vegetational noda. The overstory data are inherently more structured (i.e., contain more distinct subgroups) than those of the understory. An exception is seen with groups in which Abies balsamea plays a prominent role. These are interpreted as stages in various successions of which only one, a Betula papyrifera to A. balsamea sequence, represents the complete transition from one canopy dominant to another. The understory noda are summarized in terms of the compositional and environmental features of stands belonging to each nodum. Relationships among the understory noda are summarized in a multidimensional scaling ordination which is derived directly from similarity values (conjunction coefficients) representing the overlap between pairs of noda. Two major environmental gradients seem to affect understory composition. These are a site moisture—nutrient concentration gradient and a general fertility—productivity gradient. Canopy composition and understory vegetation are compared by nodal conjunction between the two analyses. Groups of noda, representing wet bog forests and also upland mesic forests, show moderate to good coincidence but beyond this little canopy specificity emerges. These results indicate that overstory—understory coincidence is due primarily to similar site requirements. Understory species' response to an overstory succession is examined. Many abundant herbs seem indifferent to dramatic canopy change. This observation and results from nodal component analysis are discussed with respect to forest fire.

Adaptation and acclimation of higher plants at the enzyme level: thermal properties of NAD malate dehydrogenase of two species of Aster (Asteraceae) and their hybrid adapted to contrasting habitats

Thermal and kinetic properties of NAD malate dehydrogenase (MDH) were investigated in clonal populations of two species of Aster and their hybrid: A. acuminatus, a forest understory species; A. nemoralis, a sphagnum-bog species; and A. blakei, their hybrid occurring at the bog–forest ecotone. The populations were collected within a 300 m radius in southwestern Quebec. Compared with A. acuminatus, the MDH of crude extracts from A. nemoralis had lower thermostability in both 5- and 10-min assays at 55 °C, and reduced apparent energy of activation (Ea) in the temperature range of 15–25 °C. However, these differences were not maintained in purified extracts of the species and may be attributed to higher phenolase and peptidase activity in crude extracts of A. nemoralis. The ratio of MDH activity over total protein concentration, or fresh weight leaf tissue, was higher in A. acuminatus than in A. nemoralis. Most values for these MDH properties of A. blakei were intermediate between those of the two parents. No differences, however, were observed for the substrate binding ability (Km) of MDH in the three taxa. Electrophoretic analyses show no qualitative differentiation in the enzyme profiles of MDH of the three taxa, which consist of two mitochondrial and six cytosolic isozymes. Mitochondrial isozymes were more thermostable but no differences in thermostability were observed among the forms of the species. The thermal and kinetic properties of malate dehydrogenase, as measured in situ, have not been substantially modified by the contrasting microclimatic regimes associated with the habitats of A. acuminatus and A. nemoralis.

Zur pedochemie des berylliums — untersuchungen einer bodengesellschaft im gebiet des bärhaldegranits (südschwarzwald)

The profile distribution of Be is given for a toposequence of podzols, brown earths, stagnogley, forest bog and “Ockererde” (slope gley with infiltrated Al, Mn and Fe). Analysed were the parent rock, fine earth, four fractions of mineral soil (fine skeleton, sand, silt, clay) and the needles of spruce trees. Beryllium is involved in selective weathering processes of elements. Accordingly, the Be-content increases from the fine skeleton to sand, rock, silt and clay, progressively. Through pedogenetic enrichment, Be accumulates in the mica-rich silt fraction. Uptake of Be by spruce is very low even from these acid soils. The accumulation in the needles becomes greater with increasing age. The pedochemical behaviour of Be is very similar to that of Al. Be is incorporated very little in the organic matter cycle, and is therefore not enriched in the soil humus. The brown earth has lost Be, especially in the A h-horizon. In the A e-horizon of the podzol, loss of Be is even greater; the loss is partly offset by Be-enrichment in the B-horizon. In the profiles of depressions, the Be-content is high and is ascribed to lateral flow from the slopes. Be-enrichment is especially high in horizons with a pH of about 5. The Be-balance of the watershed indicates an export of about 10% of the original amount.

Paleoecological aspects of the Red Lake Peatland, northern Minnesota

The Red Lake Peatland, situated on the eastern arm of the Lake Agassiz plain in north central Minnesota, is made up of large black spruce raised bogs separated by sedge-covered water tracks marked by string patterns and teardrop-shaped forested islands. About 3 m of peat overlie a prairie soil; the basal peat is 3170 ± 100 years old (14C date). Stratigraphic distribution of pollen, macrofossils, and peat components in a series of cores along a small forested island was used to study the development of the peatland.In pollen zone RLB-1 (lowest) the upland pollen types suggest an oak savanna with a developing mesic deciduous forest. The local pollen indicates a succession from a Typha marsh to a sedge meadow. Zone 2 shows a small rise in Pinus pollen; Ericaceae pollen and Sphagnum spores indicate the development of a bog–heath vegetation type at the coring site. An increase in pollen of spruce and larch reflects the establishment of the island forest. Zone 3 is marked by a rise in Ambrosia pollen, recording agricultural land clearance in northwestern Minnesota in about 1890.The Salix–herb macrofossil assemblage occurs at the base of some cores; it is succeeded stratigraphically by the Typha–Scirpus assemblage, which also makes up the base of the remaining cores. There follows the Carex diandra – Carex aquatilis assemblage, suggesting a sedge meadow. The overlying Menyanthes–Larix assemblage continues to the surface under the sedge fen; under the island, seeds of Chamaedaphne and needles of Picea occur in this assemblage. The incoming of the Menyanthes–Larix assemblage is believed to reflect the first development of the patterned wetland.Reed peat comprises the bottom 20–50 cm of all cores; it corresponds with the lower part of pollen zone 1 and contains the Typha–Scirpus macrofossil assemblage. Pure sedge peat or sedge peat with Bryales corresponds with zone 2 and upper zone 1 of the pollen diagram and contains the Carex diandra –C. aquatilis macrofossil assemblage. Ericaceous peat occurs only under the island, and it contains the Menyanthes–Larix macrofossil assemblage. Laterally under the present sedge fen it grades into sedge peat with ericaceous components.The general upward succession of communities observed in these peat cores can be duplicated along a west-to-east surface traverse across the present prairie–forest transition. The stratigraphic succession thus records the westward movement of the prairie–forest transition across Beltrami County about 4000–2000 years ago.The area was covered by prairie more than 3100 years ago. Development of a cooler, moister climate led to a Typha marsh in the poorly drained lowland; oak savanna occupied the surrounding upland. As the water level rose in the lowland, peat started to accumulate as sedge meadow developed, and aspen parkland and conifer–hardwood forest moved into the upland. About 2000 years ago the growth of Sphagnum moss increased, accompanied by the development of patterned wetland and bog forest, with conifer–hardwood forest on the upland.

Vegetation Changes in a Small Michigan Bog from 1917 to 1972

Quantitative descriptions of the vegetation and maps of the pool of Bryant's Bog are available for several years since 1917. The vegetation advanced into the bog pool in an irregular manner at an average rate of 2.1 cm/year. In 1972 the pool was 76% of its extent in 1926. The vegeta:tion changed in a successional series from the Chamae-daphne association of 1917 to the high bog-shrub association in the dry years of the 1920's to a bog forest which was well established in the late 1960's. It regressed in the early 1970's when many of the. trees died and the Chamaedaphne association appeared to be re-establishing itself. The most probable cause of tree mortality was flooding caused by exceptionally high water levels due to natural weather cycles. Tree mortality was also found in Hoop Lake Bog which, like Bryant's Bog, lacks aboveground drainage while none occurred in bogs with aboveground drainage.

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.

The Relationship Between Net Primary Production and Accumulation for a Peatland in Southeastern Manitoba

Two functional attributes of an ecosystem, net primary production and subsequent dry matter accumulation, were examined in four peatland types (lagg, bog, muskeg and bog forest) located in southeastern Manitoba. A preliminary peat accumulation budget was constructed by relating the amount of litter present after a single year of decomposition to the initial litter income and annual net primary production. Annual litter “income” in the four vegetation zones ranged from 489 gm/m2, which represented 69% to 90% of the calculated net primary production. Decomposition losses in the following year amounted to approximately one quarter of the original income. An average annual accumulation rate of 26 gm/m2/yr to 51 gm/m2/yr was calculated from radiocarbon—dated peat cores, thus suggesting that less than 10% of the annual net primary production will remain as peat.

Landscape Evolution, Peatland Types, and the Environment in the Lake Agassiz Peatlands Natural Area, Minnesota

The vegetation and peatland types of the Lake Agassiz Peatlands Natural Area are related to topography, waterflow patterns, water chemistry, and the evolution of the landscape as recorded by peat stratigraphy. Eight peatland types are distinguished: (1) minerotrophic swamp, (2) weakly minerotrophic swamp, (3) string bog and patterned fen, (4) forest island and fen complex, (5) transitional forested bog, (6) semi—ombrotrophic bog, (7) ombrotrophic bog (raised bog), and (8) raised bog drain. Consistent differences in pH, Ca, and Mg were found between waters of contrasting peatland types. These differences agree with the division of peatland types by degree of mineral soil water influence (minerotrophy). A general topographic alignment of vegetation and peatland types agrees with the hypothesis of chemical controls. Vegetation types often have sharp boundaries related to changes in water properties, peat surface configuration, and paths of waterflow. Landscape evolution included five phases: (1) Recession of Lake Agassiz about 11,700 years ago. (2) Organic sedimentation of local basins beginning 11,100 years ago. Aquatic peats eventually covered 6% of the substratum. (3) Development of fens, marshes, and carr during the postglacial warm—dry interval, beginning about 8,000 years ago. These peatlands built the sedge peats that now cover 46% of the substratum. Paludification caused water tables to rise, and most water basins were overgrown. (4) Invasion of minerotrophic swamp forests around the perimeter of the peatland and along substratum ridges, beginning about 5,000 years ago as the climate cooled and precipitation increased. These forests built the basal forest peats that now cover 48% of the substratum. (5) Capture of part of the watershed by Northeast Brook about 3,100 years ago, which caused a water—table divide and mineral depletion, initiated sphagnum invasion, and led to development of the present ombrotrophic raised bogs. As convexity grew, a sharp vegetation and chemical gradient developed along the limit of mineral soil water. Myrtle Lake rose steadily with paludification and now stands 11.8 ft (3.6 m) above the ridge 1 mile (1.6 km) north of the lake. Water tables rose 10—20 ft (3.0—6.1 m) over much of a 70—square—mile (181—km2) area. This history does not agree with early concepts of succession, which postulate a trend toward mesophytism with peat accumulation. The only "direction" here is a possible trend toward landscape diversity.