Pollen analysis of lake sediments was used to reconstruct the postglacial vegetation history of Hippa Island (53°31'50” N, 132°58'24” W), located on the exposed west coast of Haida Gwaii (Queen Charlotte Islands) on the northern British Columbia coast.
A 3.55 m sediment core was extracted from Hippa Lake, a small, shallow lake on Hippa Island. Five radiocarbon ages were obtained on organic-rich sediment. A linear age-depth model estimated the base of the sediment core to be 14,000 cal yr BP (12,000 14C yr BP). Pollen and spores extracted from sediment subsamples (1 cm3) taken along the length of the core were identified and counted to a minimum sum of 500 pollen and spores, except for four basal samples, which had low pollen concentrations.
Hippa Island’s vegetation history shares broad similarities to other vegetation records from Haida Gwaii and elsewhere along the British Columbia coast; however, climate fluctuations are not well recorded by the predominantly mesic pollen assemblages. The late-glacial period (14,000–13,500 cal yr BP; 12,000–11,400 14C yr BP) records a diverse herb-dominated vegetation community composed of Cyperaceae, Artemisia, Salix, and many other herbs. Transition to Pinus woodland by 13,250 cal yr BP (11,250 14C yr BP) is followed by increases in Alnus viridis and Alnus rubra, and the arrival of Picea. A decrease in Pinus and minor increases in ferns and herbs coincide with the Younger Dryas cold period; however, regression to tundra or increased Tsuga mertensiana, which characterized Younger Dryas cooling at other sites along the north Pacific coast, did not occur on Hippa Island. After 11,000 cal yr BP (9750 14C yr BP), a sharp change in vegetation occurs with Pinus, Alnus viridis, and Cyperaceae being replaced by Picea, Tsuga heterophylla and Lysichiton americanus. Despite well-documented evidence of a warmer and drier interval during the early Holocene, the composition of the mesic vegetation communities on Hippa Island was relatively stable during this time. Increases in Cupressaceae after 6000 cal yr BP (5300 14C yr BP) suggest increasing precipitation in the mid-Holocene. Modern mixed Cupressaceae-Picea-T. heterophylla forest formed by 4500 cal yr BP (4000 14C yr BP). / Graduate
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/3255 |
| Date | 27 April 2011 |
| Creators | Delepine, J. Michelle |
| Contributors | Lacourse, Terri |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Rights | Available to the World Wide Web |
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