Paul H. Glaser

Piston Corers for Peat and Lake Sediments

Two pistons corers are described which are successful in cuting the wood or undecomposed fibrous peat that characterizes many peat deposits. These modified corers are equipped with a serrated cutting edge, along with modifications to permit the core tube to be rotated back and forth, so that undecomposed fibers and roots can be cut. Complete sections of peat and even the underlying silt or sand can be acquired to a depth of several meters. The 10-cm diameter corer provides sufficient material for close-interval macrofossil and chemical analysis and for radiocarbon dating. The 5-cm corer is more portable and more convenient.

Groundwater flow in a bog- fen complex, Lost River peatland, northern Minnesota.

(1) The hydrogeology of a spring-fen mound, water track, and raised bog in the remote Lost River peatland, northern Minnesota, was investigated by measurements of the groundwater levels and chemistry of groundwater in observation wells. (2) Water-level measurements indicate that all the major physiographic features in the mire-a raised bog, spring fen, and intervening water track-are zones of groundwater discharge during parts of the year. (3) Sodium concentrations in peat pore-water change linearly with depth, indicating the upward advection of solutes in ground water. (4) Alkalinity and pH profiles indicate that acidic bog waters are neutralized below 0 5 m in the peat profile. A small change in the volume of groundwater discharge in the peatland may therefore be sufficient to neutralize the acidic waters on the bog surface and greatly affect the vegetation.

TRANSPORT AND DEPOSITION OF LEAVES AND SEEDS ON TUNDRA: A LATE-GLACIAL ANALOG*

Plant macrofossils from tundra ponds in Mount McKinley National Park, Alaska, are derived from debris that is transported in winter and deposited on snowbeds facing pond margins. As the snowbeds melt in spring this debris is released directly on the pond surface but most debris is swept to the shores downwind, where it is deposited in flotsam windrows. Assemblages of leaves and seeds from these alpine snowbeds, ponds, and flotsam windrows are dominated by leaves of Dryas octopetala, Vaccinium uliginosum, and leaves of dwarf Salix. Seeds are relatively scarce in the snow and sediment samples but comprise a large portion of the windrows, implying selective deposition. The similarity of these leaf and seed assemblages to late-glacial macrofossils of northeastern United States and northern Europe suggests that transport and depositional processes currently operating at McKinley Park are applicable to late-glacial landscapes elsewhere.

THE RAISED BOGS OF SOUTH-EASTERN LABRADOR, CANADA: CLASSIFICATION, DISTRIBUTION, VEGETATION AND RECENT DYNAMICS

(1) The mires of Labrador form a distinct geographical zonation: concentric raised bogs occur at low altitudes along the southern coast, excentric and plateau bogs extend inland to slightly greater altitudes and higher latitudes, and patterned fens occupy most of the interior north to the tundra. (2) The zone boundaries parallel contours and climatic isopleths, and the zonation is explained in terms of the effects of moisture surplus, soligenous water flow and physiography on mire development. (3) The raised bogs are similar to oceanic mires, with an extensive ground cover of Cladonia spp., absence of trees on the mire expanse, and pronounced surface patterns of broad peat hummocks and open-water pools. Three floristic noda are recognized in the phytosociological table: Cladonia stellaris-C. rangiferina-Kalmia angustifolia nodum on raised hummocks and Sphagnum rubellum-Scirpus cespitosus and Sphagnum lindbergii-Scirpus cespitosus noda in hollows. (4) As a result of the extensive cover of lichens the hummock vegetation readily burns during lightning fires, which are prevalent on the uplands. Examination of a chronosequence of stands burned in 1898, 1931, 1959 and 1975 documents the rapid resprouting of most vascular species and a gradual succession of Cladonia spp. and bryophytes. (5) The recent history of the hummock vegetation involves the alteration of Cladonia stellaris and Sphagnumfuscum, as documented by the presence of recurrence surfaces in short cores, peat monoliths, and long cores. Local factors, including fire and the lowering of the water table through pool drainage, are frequently responsible for changes in the ground cover and the degree of peat humification, and they may confound the stratigraphic interpretation of climatic change.

The development of streamlined bog islands in the continental interior of North America

Boreal peatlands within the interior of North America have developed vegetation landforms that simulate the shape of geologic landforms, such as islands and river channels. The genesis and development of these vegetation landforms can be inferred from spatial transitions from