The northern coniferous forest biome occupies a vast area below the tundra, extending completely across Canada and into interior Alaska. The biome is also referred to as the boreal forest or taiga . Compared to the arctic tundra, the climate of the boreal forest is characterized by a longer and warmer growing season. Precipitation averages 20 inches per year, but ranges from 40 inches in the eastern regions to 10 inches in interior Alaska. Available soil moisture is high as a result of cool temperature and low evapotranspiration rates.
Mineral soils are generally thin and poorly drained.
Large expanses of land are covered with thick deposits of peat and organic soils, ranging in depth from several feet to nearly a hundred. These soils have very high moisture holding capacities and are often completely saturated. A broad belt of forest-tundra transition lies along the northern edges of the boreal forest. Here, forest trees are interspersed with tundra plants, the former occupying more stable soils not subject to movement or heaving due to cyclic freezes and thaws. The former two species generally occupy wet sites with poorly drained mineral or organic soils, while white spruce is the climatic climax species on sites that are drier and higher in nutrient content.