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Northern Tree Habitats

Interior Alaskan forests have only six native tree species: white spruce, black spruce, quaking aspen, balsam poplar, larch (tamarack) and paper birch. Northern Canadian forests have all of those, plus jack pine, balsam fir and lodgepole pine. Since northern Canada and interior Alaska share the same grueling climate and extremes of daylength, why are the Canadian tree species absent from Alaskan forests? This is more puzzling when we consider that many moss, lichen and flowering plant species are circumboreal, that is, they are found throughout Siberia, Scandinavia, Canada and Alaska.

One possible explanation is that trees, being slow to produce, have not had enough time since the last glacial retreat to recolonize areas that they formerly occupied. For this reason, many foresters believe that the interior of Alaska can enjoy a greater variety of trees than naturally occur now.

This belief is shared by John Zasada and Les Viereck of the U.S. Forest Service, Institute of Northern Forestry in Fairbanks. They examined the present range of lodgepole pine and decided that the tree could survive in interior Alaska if given a chance. Lodgepole pine grows from southern California to the Yukon, in environments varying from rainy seacoasts to dry inland mountaintops, because genetically different strains have developed. Obviously, out of the whole range of lodgepole pine only a few races would be able to thrive in subarctic Alaska. The question is, which areas of the pine's range would provide the most suitable stock for the Interior?

To answer this question, seedlings were obtained from different locations in western Canada and planted at the Boreal Arboretum at the University of Alaska. After the first year, the tallest trees were those originating from the Prince George area of central and northeastern British Columbia, and the Peace River area of western Alberta. However, after seven growing seasons in Fairbanks, trees from the most northern homelands of the Dezadeash, Carmacks and Mayo areas of the Yukon are among the tallest, and the early starters from the south are now ranked at the bottom; although some of the trees from the Ft. Nelson area of British Columbia have maintained their relatively fast growth throughout the years. Only time will tell if these prove to be the superior performers. The best lodgepole pine races are faster-growing than the local spruces and larch planted in the same area; but again, only time will tell if the advantage will remain with the pine.

Why take a chance with exotics, when native trees have proven their ability to survive? Several reasons prompt testing of foreign tree species. Human activities often create and maintain new, sometimes artificial habitats that native trees are not adapted to. Exotics may have strong wood, large fruits or straight boles that are lacking in the natives. Insect pests, such as the large aspen tortrix or spruce budworm, may find introduced trees undesirable, and thus be prevented from building up epidemic size populations. Finally, curiosity and the desire to grow the unusual and the beautiful prompts many people to experiment with exotics. Further testing of trees from northern countries will enhance the diversity and usefulness of our native landscape.