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UBC Theses and Dissertations

The reproduction, establishment, and growth of white spruce in the forest tundra ecotone of the Inuvik-Tuktoyaktuk region Walker, Xanthe


Climate is considered one of the most important factors controlling tree reproduction, establishment, and growth at the treeline. As climate change continues the latitudinal treeline is expected to shift northwards. The main objective of this research was to characterize the ecological patterns and processes of Picea glauca (Moench.) Voss. (white spruce) in the Tuktoyaktuk region of the Northwest Territories, Canada. In particular, this study aims to determine how climate influences white spruce tree reproduction, establishment, and growth throughout the forest-tundra transition zone. A total of four forest stand sites and eight tree island sites, examined in the early 1990s, were located and re-examined in the summer of 2009. Cone production has increased since the early 1990s and cone production decreases northward across the forest-tundra. Germination rates significantly decrease with increasing latitude but have not significantly changed since they were last examined 15 years ago. In June 1994 seedlings were transplanted at three tree island sites, survivorship of these seedlings ranged from 3 to 20%. A search for true seedlings was also completed, however, none were found. Basal cores were obtained from numerous individuals within each of the sites and an age structure was developed. Establishment of individuals coincided with decades classified as cool and wet. The yearly diameter growth of each tree was determined via ring width measurements and using principal component analysis two chronologies were built, one for forest stands and one for tree islands. The chronologies were correlated to climate data of temperature and precipitation from the Inuvik airport. In general, growth was negatively correlated to previous growing season temperature and positively correlated to current season temperature. Results from this study indicate that tree islands are not likely to be important in supplying viable seed for the infilling of trees in the forest tundra, rather infilling will more likely occur from increased seed production in trees at or just south of treeline. Under proposed climate change scenarios the establishment of new seedlings will likely be negatively affected by the warmer and drier conditions, whereas the radial growth of individuals will likely increase with warming temperatures.

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