Post-glacial climate and vegetation change in the Seymour-Belize inlet complex, central coastal British Columbia, Canada

Pollen and spores preserved in the sediments of Two Frog Lake and Tiny Lake in the Seymour-Belize Inlet Complex of the central mainland British Columbia coast, document post-glacial changes in regional climate and vegetation and a high-resolution (26-year) palynological record from Frederick Sound reveals that the late Holocene climate of the Seymour-Belize Inlet Complex has been variable. Following ice-retreat prior to 11,040+/-50 (13,030 cal. yr BP), an open Pinus contorta woodland developed under a cool and dry early Late-Glacial climate. At ca. 11,800 yr BP (ca. 14,500 cal. yr BP) climate amelioration resulted in the replacement of these woodlands by a mixed conifer forest. Early Holocene warming ca. 10,500 yr BP (ca. 12,000 cal. yr BP) resulted in a successional mosaic of Tsuga heterophylla, Picea, Pseudotsuga menziesii and Alnus at Two Frog Lake but P. menziesii was absent at Tiny Lake where conditions may have been too wet or because this taxon never reached this more northerly site. At ca. 8000 yr BP (ca. 9200 cal. yr BP) a transition to moister and cooler conditions facilitated the expansion of T. plicata at both lake sites. The timing of this event pre-dates the onset of a near modern climate in south coastal British Columbia by at least 1000 years, but is consistent with the onset of moistening at more northerly sites. The Frederick Sound record documents a decline in T. plicata between ca. 2600-1900 yr BP (ca. 2700-1900 cal. yr BP) in response to the development of a cooler and drier climate that punctuated the otherwise wet conditions of the late Holocene in this region, although the role of biotic factors, such as a pathogen attack and/or selective human felling, cannot be ruled out. Comparison with a proxy reconstruction of the relative position and/or intensity of the Aleutian Low pressure system suggests that millennial scale atmospheric variability has affected the climate and vegetation of the Seymour-Belize Inlet Complex throughout most of the late Holocene.