Document: AND-3-34-15

Spatial variability in 20th century tree growth at arctic and alpine treelines in Alaska.

LLOYD, A.H.* and C.L.FASTIE

Middlebury College, Middlebury VT 05753 ¹

Abstract:
Twentieth century growth patterns of white spruce (Picea glauca) at arctic treeline and alpine treeline in Alaska vary on relatively fine spatial scales and among regions. The growth of spruce <50 m elevation below treeline in theWhite Mountains of interior Alaska has declined since the early 1900s and is inversely correlated with summer temperature. The growth of spruce at and above treeline at the same sites has increased through the 20th century and is positively correlated with summer temperature. Growth patterns also vary among regions. For example, the growth decline observed in spruce <50 m below treeline in the White Mountains was not found at sites south of Fairbanks in the Alaska Range. The relationship between spruce growth and climate is similarly variable among regions: Spruce growth in the interior is primarily correlated with summer temperature, while spruce growth at arctic treeline seems to be most strongly related to spring temperatures and snowpack. These results suggest that the effects of 20th century warming are not uniform at all treeline sites, and that there may be abrupt thresholds in response of spruce growth to climate at treeline.

Keywords: treeline, tree-ring analysis, climate change

This abstract is being presented at: 3:30 PM in session:
CLIMATE CHANGE