The Taiga biome is mainly represented by the northern coniferous forests. Spruce, Hemlock and Fir trees are present as well as Willow and Birch. The biome is characterized by long cold winters with little precipitation, and short summers with high precipitation (Raven and Johnson, 1992).
Alders are common in these conditions, which is important in terms of colonization. Alders harbor nitrogen fixing bacteria in nodules on their roots. As a result they are able to colonize raw infertile soils such as those left behind by retreated glaciers (J.D. Sauer, 1988).
Northern Alberta Taiga, A. Stoddart