Needle-leaved but deciduous, tamarack are common trees in boreal forests. Photo copyright USDA, NRCS, 1997 - Northeastern Wetlands Flora - PLANTS database.
| The boreal forest is a band of coniferous trees that spreads across North America, Europe, and Asia and, before logging and settlement, nearly encircled the northern latitudes of the globe. This is a land of "Christmas trees": spruce, pine, and fir. In more northern areas, the boreal forest gradually thins out into patches of small, scraggly trees, and eventually open tundra. There are also some areas at high elevations where the boreal forest can extend much farther south than usual, for example in the Appalachian Mountains. |
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Needle-leaved but deciduous, tamarack are common trees in boreal forests. Photo copyright USDA, NRCS, 1997 - Northeastern Wetlands Flora - PLANTS database. |
Biodiversity generally appears to be low in this region, with large areas being dominated by a single species of tree. Much of the life in these forests is hidden. The numbers of large animals are relatively low, and in the winter there can be areas of seemingly "empty" forest. Although there may be as few as 10 tree species in an entire forest, there are several thousand species of mycorrhizal* fungi growing underground. |
Eastern white pine have long, tough needles. Photo copyright USDA, NRCS, 1997 - Northeastern Wetlands Flora - PLANTS database.
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| Dead branches tend to collect around the bases of trees, and areas of forest can become too thick and dark for any smaller plants to grow. The ground is thick with fallen needles, which are tough and do not decompose easily. The cold conditions and short growing season greatly reduce the speed at which bacteria can break things down, so the soil remains poor. |
 Larch tree in winter. Photo by Al Walters. |
| Some boreal forest trees, such as White Spruce, Black Spruce, and Balsam Fir, have the largest ranges of any North American trees. | Trees can only access the nutrients from fallen needles with the help of fungi. Webs of these fungi surround the trees' large, shallow root networks. Extending upwards, the fungi break down the needles into chemicals that can be absorbed by trees. The fungi benefit by receiving other nutrients, which they can't create for themselves, directly from the tree roots. |
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In certain areas it is possible to find a few broad-leaved trees in scattered patches, but trees in the boreal forest are almost exclusively needle-leaved evergreens. The needles are thin and arranged in patches, helping to shed snow and block wind. They have a waxy coating which helps prevent water loss, and contain a thick, sugary sap that prevents freezing in the winter. These needles influence the numbers and types of animals that live in the boreal forests. They can not support the large numbers of vegetarian species which, in more southern regions, munch away at the softer, more digestible leaves of broad-leaved trees. Needles are nearly inedible to everything from caribou to small rodents to most birds. |
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One of the coldest recorded temperatures in a boreal forest was -40 degrees Celsius, which is even lower than the coldest tundra temperatures. |
| 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. |
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| 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. |
| The ground in a boreal forest is often covered with snow, but the soil is frozen, which means there is as little water available to trees as in a southern desert. | In the winter, all boreal forests around the world have a very similar appearance. Many of the same species live on several different continents, and there are other closely related species that appear similar. However, in the summer, the character of the forest changes. Animals from farther south migrate to the boreal forest to feed on everything from lemmings to caterpillars to seeds, which all appear in great numbers during the region's brief warm season. |
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[fungi] [biodiversity] [soil] [broadleaf forest] [water] [seasons] [forest life] [mammals] [birds] [seeds]
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