Late Quaternary Vegetation History of White Pass, Northern British Columbia, Canada

Abstract

Paleoecological investigations at two sites in the White Pass, Drizzle Pond, and Waterdevil Lake, provide a record of late-Quaternary vegetation change in this mountainous region of northern British Columbia. The vegetational sequence at Waterdevil Lake (875 m a.s.l.) has four stages: (1) shrub tundra with alder (Alnus crispa) and dwarf birches (Betula glandulosa/nana) from 10.5 to 8.5 ka; (2) shrub tundra with alder and dwarf birches plus juniper (Juniperus communis) on drier microsites from 8.5 to 5.2 ka; (3) spruce (Picea) woodland from 5.2 to 4.0 ka; and (4) open woodland with lodgepole pine (Pinus contorta) and subalpine fir (Abies lasiocarpa) from 4 ka to the present. Alpine shrub tundra has persisted around Drizzle Pond (910 m a.s.l.) throughout the Holocene and only varied slightly in composition.The fossil record demonstrates that White Pass did not serve as a migration route for those major tree and shrub species that occur on both the coastal and interior sides of the pass. Because the highest elevations in the pass have always been in alpine tundra, it is unlikely that trees could have crossed the divide. Although subalpine fir, spruce (probably white spruce), lodgepole pine, mountain hemlock (Tsuga mertensiana), and alder occurred within the White Pass during the Holocene, the timing of their arrival there in comparison with arrival times on the coast and interior also indicates that the pass was not the route by which these species entered the interiors of British Columbia or the Yukon Territory.