The boreal forests are dominated by coniferous evergreens, chiefly balsam fir, black spruce, jack pine, and white spruce. Some areas support stands of larch, which is a deciduous conifer. Such deciduous broadleaf trees as balsam poplar, trembling aspen, and white birch grow in areas that have been burned over by forest fires. Some of the bogs are treeless. Other bogs, called muskegs, are covered by a deep mat of moss on which dwarfed conifers grow.
Subarctic woodlands lie along the northern edge of the boreal forests.
The climate in this region is bitterly cold, with low precipitation and an extremely brief growing season. These conditions force the trees to grow in a widely spaced, savannalike fashion. Black spruce dominates most of the region. Other boreal trees, such as aspen, larch, white birch, and white spruce, grow in some places. North of the woodlands lies the Arctic tundra, where trees cannot survive.