Evergreen forests have long, cold winters lasting six months or longer. The summers are rainy and have moderate temperatures ranging from 20 to 70 degrees Fahrenheit. Summer and winter lead into each other, with little opportunity for milder spring and fall temperatures.
Evergreens dominate this climate due to their ability to tolerate the long, cold winters. Wax on the needles provides protection from the cold, allowing the trees to retain the needles throughout the winter. This needle retention allows evergreens to begin photosynthesis as soon as the weather begins to warm, saving valuable time in the growth process. The pyramid shape of evergreen trees allows them to shed heavy snow, preventing damage to the trees from breaking limbs.
Predators dominate evergreen forests, feeding on small herbivores that live in the understory of the evergreen trees. A prevalence of insects tempts birds to come to evergreen forests for breeding. These birds migrate to other areas once the breeding season is over. The availability of seeds entices some birds to stay in the area all year long.
Fires occur often in the evergreen forest. These fires burn away the upper canopy, allowing sunlight to reach the ground and change the environment of the understory.