Pacific temperate rainforests

The Pacific temperate rainforests of western North America is the largest temperate rain forest region on the planet as defined by the World Wildlife Fund (other definitions exist). The Pacific temperate rainforests lie along the western side of the Pacific Coast Ranges along the Pacific Northwest Coast of North America from the Prince William Sound in Alaska through the British Columbia Coast to Northern California, and are part of the Nearctic realm, as also defined by the World Wildlife Fund. The Pacific temperate rain forests are characterized by a high amount of rainfall, in some areas more than per year and moderate temperatures in both the summer and winter months (). This ecoregion is a subregion of the Cascadia bioregion. These rainforests occur in a number of ecoregions, which vary in their species composition, but are predominantly of conifers, sometimes with an understory of broadleaf trees, ferns and shrubs. In the WWF's system, the ecoregions of the Pacific temperate rainforests are the Northern Pacific coastal forests, Haida Gwaii, British Columbia mainland coastal forests, Central Pacific coastal forests, Central and Southern Cascades forests, Klamath-Siskiyou forests, and Northern California coastal forests ecoregions. The forests in the north contain predominantly Sitka spruce (Picea sitchensis) and western hemlock (Tsuga heterophylla), while those in the coastal forests are home to both species mentioned, as well as coast redwood (Sequoia sempervirens), coast Douglas-fir (Pseudotsuga menziesii), western redcedar (Thuja plicata) and shore pine (Pinus contorta). Notably, many of the world's largest and tallest tree species are found in this ecoregion. Dense growths of epiphytes and mosses cover the trees, and lush vegetation is present everywhere. Hardwood trees such as the bigleaf maple and the alder are also common, especially at lower elevations and along stream banks, and are vital to the ecosystem, in part because of their nitrogen fixing.