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CR 36:123-130 (2008)  -  DOI:

Climate and nutrient influences on the growth of white spruce trees in the boreal forests of the Yukon

Rudy Boonstra1,*, Lanna Desantis1, Charles J. Krebs2, David S. Hik3

1Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario M1C 1A4, Canada
2Department of Zoology, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
3Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada

ABSTRACT: The boreal forests of North America are undergoing major changes because of the direct effects of global warming and increased CO2 levels. Plant production in the boreal forest is nutrient limited, and we examined how long-term fertilization affected growth of white spruce Picea glauca in the face of these major changes. We conducted a large-scale experiment by fertilizing two 1 km2 stands of white spruce in the southwestern Yukon with commercial NPK fertilizer from 1987 to 1994. Tree growth was measured by the width of annual increments in 60 trees from each of 2 control and of 2 matched fertilized 1 km2 sites for the period from 1977 to 1997 in a before, during, and after experimental design. Ring widths increased in both control and fertilized trees over this period as summer temperatures increased. Ring widths in fertilized trees increased from 9 to 48% over control trees during the years in which fertilizer was added, but immediately fell back to control levels from 1995 to 1997 at 1 site as soon as fertilization was stopped. In the long term, nitrogen in these forests may become tied up in shrubs, grasses, herbs, and fungi and not be available to the trees. There are 2 other possible explanations for this lack of sustained tree growth: first, the conversion of nitrogen into a form not readily available to spruce and, second, a spruce bark beetle outbreak that hit the southwestern Yukon during and after 1994 and affected 1 study site much more than the other.

KEY WORDS: Climate change · Nitrogen limitation · Picea glauca · Primary productivity · Spruce bark beetle · Tree ring widths · Yukon · Kluane Lake · White spruce

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Cite this article as: Boonstra R, Desantis L, Krebs CJ, Hik DS (2008) Climate and nutrient influences on the growth of white spruce trees in the boreal forests of the Yukon. Clim Res 36:123-130.

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