BRITISH-COLUMBIA VEGETATION AND CLIMATE HISTORY WITH FOCUS ON 6 KA BP

British Columbia Holocene vegetation and climate is reconstructed from pollen records. A coastal Pinus contorta paleobiome developed after g lacier retreat under cool and probably dry climate. Cool moist forests involving Picea, Abies, Tsuga spp., and Pinus followed until the earl y Holocene. Pseudotsuga menziesii arrived and spread in the south 10 0 00-9000 BP, and Picea sitchensis - Tsuga heterophylla forests develope d in the north. T. heterophylla increased 7500-7000 BP, and Cupressace ae expanded 5000-4000 BP. Bogs began to develop and expland. Modern ve getation arose 4000-2000 BP. There were early Holocene grass and Artem isia communities at mid-elevations and pine stands at high elevations in southern interior B.C. Forests expanded downslope and lakes formed 8500-7000 BP. Modern forests arose 4500-4000 BP while lower and upper tree lines declined. In northern B.C. non-arboreal communities precede d middle Holocene Picea forests. Abies, Pinus and Picea mariana predom inated at various sites after 4000 BP. At 6000 BP Tsuga heterophylla ( south) and Picea sitchensis (north) dominated the coast and islands an d Quercus garryana and Pseudotsuga on southeast Vancouver Island, but Thuja plicata was infrequent. Southern Interior Plateau Vegetation at 6000 BP was more open than today at middle to lower elevations, wherea s forests covered the Northern interior Plateau. Picea forests occurre d in northern B.C. Holocene climate phases were : 1) warm dry ''xeroth ermic'' ca. 9500-7000 BP, 2) warm moist ''mesothermic'' ca. 7000-4500 BP, 3) moderate and moist 4500-0 BP, with increasing moisture 8500-600 0 BP and cooling (?increased moisture) 4500-3000 BP. B.C.'s Hypsitherm al had dry and wet stages; 6000 BP occurred in the warm and wet mesoth ermic stage.