White spruce is the predominant tree species in the Boreal White and Black Spruce (BWBS), except in the Fort Nelson area where the poorly drained lowlands are dominated by black spruce.
Mixed stands of white spruce and trembling aspen (often with a minor component of balsam poplar [Populus balsamifera], birch (Betula papyrifera, B. neoalaskana) or lodgepole pine) are the most common components of forest cover on warm mesic sites in the BWBS.