Author (Your Name)

John Dawson, Colby College

Date of Award


Document Type

Senior Scholars Paper (Open Access)


Colby College. Biology Dept.


Nelson, Robert E.


A 6-m vibracore taken from the Great Bog in Belgrade, Maine, was sampled for pollen analysis at 10-cm intervals. Samples were processed in the laboratory using standard techniques developed by Faegri and Iversen. The sediment in the sample was reduced to a residue of pollen which was mounted on microscope slides. A minimum of 300 pollen grains was identified and counted at each level using a compound microscope at 400x magnification. Five radiocarbon dates were taken from the core at stratigraphic boundaries. Lastly, pollen concentration and pollen accumulation rates were calculated. The uppermost 3.8 m of the core is fine peat; this overlies 1.5 m of lacustrine clay below which are additional organic deposits. Approximately 1.5 m of silty clay was lost from the bottom of the core during coring. 14C dates from above and below the clay are statistically equivalent, suggesting very rapid deposition; a basal date on the core is also statitically equivalent in age , but is probably contaminated. Rapid deposition of the clay could have been caused by mass wasting or upland denudation. Dramatic erosion of the uplands could be caused by clearing of vegetation by a forest fire, but this is not supported by any significant, charcoal in the core. Additional work is planned to delimit the areal extent of the clay unit and resolve the apparent dating anomalies in the lower core. Although the post-glacial pollen record generated in this study at Great Bog is incomplete, it is highly detailed. The pollen record indicates that the Great Bog was an open embayment of Great Pond from 8,500 to 6,500 b.p. The change in the aquatic vegetation at the site from the open-water taxa Nuphar, Nymplwea, and Brasenia to Eriocaulon and abundant Sphagnum spores suggests that the water level at Great Bog may have dropped and subsequently allowed a Sphagnum mat to develop. It is possible that this occurred at the same time as a mid-Holocene drop in water level of lakes throughout Maine. Pinus dominated the regional vegetation also until 6,500 b.p. when Tsuga and Fagus appeared in significant percentages. Tsuga had a temporary demise around 4,000 b.p. that is recorded regionally and was possibly caused by a pathogen. At 30-cm depth, there was an increase in Ambrosia, which reflects agricultural clearing at the start of European colonization of this region.


Bogs, Maine, Belgrade Region, Bog ecology

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