HR: 0800h
AN: PP51C-0659    [Abstracts]
TI: Radial growth response of white spruce ( Picea glauca) to climatic conditions, Mackenzie Delta, NWT
AU: * King, G M
EM: gking2@connect.carleton.ca
AF: Carleton University Department of Geography and Environmental Studies, 1125 Colonel By Dr. B349 Loeb Building, Ottawa, ON K1S5B6, Canada
AU: Pisaric, M F
EM: michael_pisaric@carleton.ca
AF: Carleton University Department of Geography and Environmental Studies, 1125 Colonel By Dr. B349 Loeb Building, Ottawa, ON K1S5B6, Canada
AU: Kokelj, S V
EM: kokeljsv@inac-ainc.gc.ca
AF: Water Resources Division Indian and Northern Affairs Canada, P.O. Box 1500, Yellowknife, NT X1A 2R3, Canada
AB: In Canada, 20th century air temperature warming has been greatest in the western Arctic.The prevailing theory of vegetation response to climate suggests warmer temperatures will result in increased growth of trees. However, a number of dendroecological studies from northwestern North America have highlighted a divergence in growth trends during recent decades. Several possible reasons for this response have been suggested. These include warmer temperatures that are exceeding the physiological threshold of white spruce, increased temperatures contributing to drought stress as precipitation is insufficient to offset increasing water demands or possibly large- scale processes such as changes in stratospheric ozone concentration or the effects of global dimming on photosynthetic rates. Here we document additional evidence for sites within the Mackenzie Delta showing a similar divergence trend with regional growing season temperatures. Additionally not all trees at a single site are responding similarly, with many more trees (~75%) having inverse climate-growth responses (negative responders). A much smaller subset continues to exhibit the traditional climate-growth response for treeline species - warmer temperatures equating to greater growth (positive responders). This study will investigate how environmental conditions influence tree growth within the Mackenzie Delta as the growing season progresses. Radial growth of white spruce trees is measured using automatic, high-resolution sensors (point dendrometers). These measurements are compared with environmental data (ground and air temperatures, precipitation, soil moisture, thaw layer depth and solar radiation) collected in-situ so that the critical factors associated with white spruce growth could be determined. The automatic growth sensors and environmental data were installed and monitored for two consecutive growing seasons at a site located north of Inuvik, NT. Tree cores were collected from 42 trees at the site including each of the instrumented trees to determine growth response over time. Measurements of active layer depth, tree health, competition and reproductive success were collected for each sampled tree to determine if any of these characteristics are related to the observed divergence with summer temperatures. This research has implications for the accurate modeling of future carbon sequestration rates within the boreal forest as well as accurate reconstruction of past climatic conditions and environments.
DE: 1630 Impacts of global change (1225)
DE: 1637 Regional climate change
DE: 9315 Arctic region (0718, 4207)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting