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Presents a study that investigated the rates of peat accumulation during the postglacial period in several sites from Alaska to Newfoundland, with special emphasis on northern Minnesota. Relationship between mass and age; Locations of sites from which peat cores were collected; Influence of age on accumulated dry mass in North American peat deposits.

Examines the regional associations between raised bogs and the climate, groundwater and landscape of northwestern Minnesota. Absence of relation to the westward climatic gradient; Groundwater movement during droughts; Relation of bogs to physiographic features.

Two peat mounds have developed in the Lost River peatland of northern Minnesota. One has the chemical and physical properties of an extremely rich fen and the other has the properties, of a raised bog. The two mounds are separated by a water truck with poor-fen vegetation and chemistry. The vegetation at Lost River can be divided into live noda that correspond to landform units: spring-fen channel, springs fen forest, marginal swamp forest, water track, and raised bog. These vegetation types have well-defined ranges for pit and calcium concentration. Ordinations of the vascular plant and bryophyte data indicate a close relationship between the vegetation and both moisture and chemical gradients. The link between vegetation and chemistry is also supported by plots of species richness vs. pH and calcium concentration in which the peak in species numbers occurs within the rich-fen range. The chemistry of the surface waters at Lost River is largely determined by the mixing of alkaline groundwater with precipitation, because the entire peatland is located at least seasonally within a discharge zone for groundwater. Mixing models indicate that the amount of groundwater within the surface waters ranges from 50% in the spring-fen channels to 1% on the raised bog. The development of the two Feat mounds was reconstructed from peat cores collected near the crests of the spring-fen mound and raised bog. The raised bog developed over a depression, which was first filled in with ten peat before minerotrophic sphagna invaded the site around 2625 B.P. By 2200 B.P. all fen indicator species had disappeared and the site was dominated by assemblages similar to those in the present raised bog. The spring-fen mound, however, developed over m rise in the mineral substrate, which was not covered by peat until 3000 B.P. The mound was quickly colonized by Sphagnum and no fen indicators appeared until 1160 B.P. At this time the bog vegetation was replaced by a sedge fen containing assemblages similar to the present spring-fen channel. This sharp reversal from bog to fen under the spring-fen mound can best be explained by the discharge of alkaline groundwater at the peat surface in sufficient quantities to convert the bog vegetation to a spring-fen channel. [ABSTRACT FROM AUTHOR]

(1) Red Lake Peatland m northern Minnesota covers an area of about 80 × 15 km which is uninterrupted by streams or uplands and consists of a vast patterned complex of rinsed bogs and water tracks. Infra-red photography and LANDSAT imagery have been used to examine their interrelationships (2) To the west a large water track up to 5 km broad carries minerotrophic water from uplands adjacent to the peatland. This western water track is differentiated into a series of transverse ridges (strings) and linear pools (flarks), among which are much larger teardrop-shaped islands consisting of a forested head and a long tail of dwarf birch (Betula pumila var glandulifera) leading downslope. (3) Rinsed bogs with radiating lines of spruce trees and 'bog drains' form the watershed divides to the east. The bogs are fringed downslope by non patterned Sphagnum lawns on which incipient water tracks arise. These recipient tracks lead downslope into well-defined water tracks that flow between other rinsed bogs apparently shaping these bogs into ovoid islands several kilometres long. (4) The major types of vegetation of the Red Lake Peatland were determined subjectively by the Braun-Blanquet method and are characterized by different water chemistry (5) Two types of bog vegetation occur on the rinsed bogs and ovoid islands. They have waters of low pH (range 3.8-4.1), low Ca[sup 2+] concentration (range 0.5-2.1 mg l[sup -1]) and low conductivity. K[sub corr] (range 12-50 ·S cm[sup -1]). (6) Three types of fen vegetation occur on stnngs, flarks and teardrop islands in the water tracks these fens are characterized by high pH (range 5.2-7.0), high Ca[sup 2+] concentration (range 3.0-19.6 mg l[sup -1]) and high K[sub corr] (range 23-128 µS cm[sup -1]). (7) Poor fens closely resemble bog or fen vegetation, but they may be distinguished by their location water chemistry and the presence or absence of certain indicator species. Poor fens occur on the broad Sphagnum lawns... [ABSTRACT FROM AUTHOR]