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Growth dynamics, needle morphology, and needle retention on white spruce in three Alaskan mountain ranges.
Traustason, Tumi 1, Smith, Matthew 1, Sveinbjornsson, Bjartmar 1, Ruess, Roger2, 1 2
ABSTRACT- White spruce (Picea glauca (Moench) Voss) is the dominant treeline species in Alaska. In this study, we measured its annual extension growth, needle morphology and determined its needle retention in three mountain ranges in Alaska: the Chugach Mountains, White Mountains, and the Brooks Range. We hypothesized that needle retention would increase while growth decreased with increasing latitude. Treeline sites were expected to show both decreased growth and needle retention in comparison to forest sites. Five branches were harvested from the windward side and five from the leeward side of 3-5m tall trees from treeline and forest sites at three separate locations within each mountain range. Our preliminary results indicate that there is twice as much lateral growth in the Chugach Mountains than in the two interior mountain ranges. Needle retention was highest in the Brooks Range and lowest in the Chugach Mountains. In the Chugach Mountains there were great differences in needle retention and lateral growth between the forest and treeline sites while elevation differences were smaller in the two interior mountain ranges. Apart from longer needle in the Chugach forest, latitudinal and elevational differences in needle length were minor. The above results indicate that the coastal Chugach Mountains have greater annual growth and have higher variation between treeline and the forest.
KEY WORDS: Treeline, Needle retention, Picea glauca