2002 ARCSS All-Hands Workshop

Reproductive and vegetative responses of Cassiope tetragona to experimental warming from 1986-1998 at Alexandra Fiord, Ellesmere Island, Canada

Shelly A. Rayback¹, Greg H. Henry^2
1Department of Geography, University of British Columbia, 217-1984 West Mall, Vancouver, BC, V6T 1Z2, Canada, Phone 206-352-3849, rayback@interchange.ubc.ca
²Department of Geography, University of British Columbia, 217-1984 West Mall, Vancouver, BC, V6T 1Z2, Canada, Phone 604-822-3441, ghenry@geog.ubc.ca

General circulation models (GCMs) of the Earth's atmosphere predict significant climate change in the high latitudes within the first half of the twentieth century due to the effects of anthropogenically enhanced greenhouse gases in the atmosphere (Maxwell 1992; Houghton et al. 1996). By employing a common temperature manipulation, the International Tundra Experiment (ITEX) seeks to understand variability in arctic and alpine species' response to increased warmth across climatic and geographic gradients of tundra ecosystems (Henry and Molau 1997; Arft et al. 1999). This study investigates the vegetative and reproductive response of one of the core ITEX species, the circumpolar evergreen dwarf shrub, Cassiope tetragona to seven years (1992-1998) of experimental warming at Alexandra Fiord, Ellesmere Island, Canada. Plant stems from Cassiope tetragona plants were harvested at the end of the 1998 growing season from four plot pairs in a mesic tundra community. Using retrospective analysis, annual growth increments were determined from leaf internode distance measurements. The annual production of leaves, flower buds and flower peduncles were counted as well. Multiple analysis of variance and multiple analysis of covariance showed no significant differences in annual growth increments or in the annual production of leaves between the pre-treatment (1986-1991) and treatment (1992-1998) periods. However, reproductive effort was significantly greater during the treatment period. These results support some short-term experimental warming studies of Cassiope tetragona, confirming an absence of a significant vegetative response (Johnstone 1995; Molau 1997), but a significant increase in reproductive effort due to increased growing season temperatures (Nams 1982; Johnstone 1995). Recent work has explored the relationship between climatic conditions and the two growth and reproductive variables during the pre-treatment and treatment periods.

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