Late Quaternary vegetation, climate, fire history, and GIS mapping of Holocene climates on southern Vancouver Island, British Columbia, Canada

• Main Author: Brown, Kendrick Jonathan
• Other Authors: Hebda, Richard Joseph
• Format: Thesis
• Language: English
• Published: 2000
• Subjects: Geology; Stratigraphic; Quaternary; Holocene; Vancouver Island (B.C.); British Columbia; Canada; Porphyry Lake; Tundra
• Online Access: https://dspace.library.uvic.ca//handle/1828/9045

Pollen and microscopic charcoal fragments from seven sites (East Sooke Fen and Pixie, Whyac, Porphyry, Walker, Enos, and Boomerang lakes) were used to reconstruct the post-glacial vegetation, climate, and fire disturbance history on southern Vancouver Island, British Columbia, Canada. A non-arboreal pollen and spore zone occurs in the basal clays at Porphyry Lake and likely represents a tundra or tundra-steppe ecosystem. This zone precedes the Pimis contorta (lodgepole pine) biogeochron that is generally considered to have colonised deglaciated landscapes and may represent a late Wisconsinan glacial refugium. An open Pinus contorta woodland characterised the landscape in the late-glacial interval. Fires were rare or absent and a cool and dry climate influenced by “continental-scale katabatic” easterly winds dominated. Closed lowland forests consisting of Picea (spruce), Abies (fir), Tsuga heterophylla (western hemlock), and Tsuga mertensiana (mountain hemlock) with P. contorta and Alnus (alder) and subalpine forests containing Picea, Abies, and T. mertensiana with P. contorta replaced the P. contorta biogeochron in the late Pleistocene. Fires became more common during this interval even though climate seems to have been cool and moist. Open Pseudotsuga menziesii (Douglas-fir) forests with Pteridium (bracken fern) in the understory and Alnus in moist and disturbed sites expanded westward during the warm dry early Holocene. At this time closed Picea, T. heterophylla, and possibly Alnus forests grew in the wettest part of southern Vancouver Island at Whyac Lake. At high elevations, forests consisting of T. heterophylla and Pseudotsuga coupled with Alnus expanded during the early Holocene. Fires occurred frequently in lowland forested ecosystems during this interval, although East Sooke Fen in a dry, open region experienced less fire. At high elevations, charcoal increased somewhat from the late Pleistocene, indicating slightly more fires and reflecting continued moist conditions at high elevations. The mid and late ...