Shades of Green: Earth's Forests -- Forest Types

It is the seeds which are produced in vast numbers in the cones of evergreen trees that support animals of the boreal forest. The crossbill, a type of finch, has a specially developed beak just to make the task of removing seeds from seed cones easier. Other birds and small mammals feed on the seeds, often storing them away for later use.

Alaskan boreal forest. Photograph courtesy Philip Greenspun.

The growing season in the boreal forest can be as short as one month a year. Even lower light levels farther north are what keep the boreal forest from spreading into the tundra.

So many seeds can be eaten by mammals such as lemmings that some years there aren't many left to germinate. Every few years, after an unusually warm summer or after the trees have had time to store up enough energy, an exceptionally large number of seeds is produced, ensuring that there will be plenty left over after mammals and birds have eaten. However, the seed-eating animals are also a great help to the trees. By inadvertently spreading seeds over great distances, they help trees extend their ranges.

To conserve heat, the mammals that do live in the boreal forest tend to be large: moose, which are the largest type of deer, wolverines, which are the largest weasel, and the largest species of grouse all live in boreal forests. Aside from these very large, conspicuous animals, many of the mammals in these forests are either rodents, including porcupine and squirrels, or small insect-eaters such as shrews. Common birds include jays and ravens, grouse, and crossbills. In the summer, large flocks of songbirds migrate north to the boreal forests.

Snowshoe hare can be extremely numerous in the boreal forest, though their populations change dramatically from year to year with the amount of available food. In turn, the populations of carnivores such as lynx change with the number of snowshoe hare. Both of these animals are specially adapted for the particular characteristics of boreal areas: the snowshoe hare have brown fur in the summer, but change color with the seasons and are white in winter to blend in with the snow; the lynx have very wide paws so they can run on top of the snow, which makes it easier for them to catch snowshoe hare. The hares feed on bark and leaves, and sometimes girdle small trees.

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[mammals] [birds] [seeds]

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