In North America, it covers most of inland Canada, Alaska, and parts of the northern contiguous United States. In Eurasia, it covers most of Sweden, Findland, much of Norway and Estonia, some of the Scottish Highlands, some lowland/coastal areas of Iceland, much of Russia from Karelia in the west to the Pacific Ocean (including much of Siberia), and areas of northern Kazathstan, northern Mongolia, and northern Japan (on the island of Hokkaido.
The taiga has a subarctic climate with very large temperature range between seasons, but the long and cold winter is the dominant feature. Temperatures vary from - 540C to 300C throughout the whole year. The summers, while short, are generally warm and humid. In much of the taiga, −200C would be a typical winter day temperature and 18 0C an average summer day.
There are two major types of taiga. The southern part is the closed canopy forest, consisting of many closely spaced trees with mossy ground cover. In clearings in the forest, shrubs and wildflowers are common, such as the fireweed. The other type is the lichen woodland or sparse taiga, with trees that are farther-spaced and lichen ground cover, the latter is common in the northernmost taiga.
The forests of the taiga are largely coniferous, dominated by larch, spruce, fir and pine. Taiga trees tend to have shallow roots to take advantage of the thin soils, while many of them seasonally alter their biochemistry to make them more resistant to freezing, called "hardening". Although the taiga is dominated by coniferous forests, some broadleaf also occur, notably birch, aspen, willow, and rowan. Many smaller herbaeous plants, such as ferns and occasionally ramps grow closer to the ground.
The taiga, supports a relatively small range of animals due to the harshness of the climate. Canada's boreal forest includes 85 species of mammals, 130 species of fish, and an estimated 32,000 species of insects. The taiga is home to a number of large , such herbivorous mammals as moose and reindeer/caribou. The largest animal in the taiga is the wood bison, found in northern Canada, Alaska and has been newly introduced into the Russian far-east. More than 300 species of birds have their nesting grounds in the taiga. Siberian thrush, white – throated sparrow, and black – throated green warber migrate to this habitat to take advantage of the long summer days.
According to en.wikipedia