Electronic Thesis and Dissertation Repository

Degree

Master of Science

Program

Biology

Supervisor

Danielle Way

Abstract

Elevated temperatures and CO2 will alter carbon flux in two dominant boreal tree species Picea mariana (black spruce) and Larix laricina (tamarack). Trees were grown in three temperature treatments (ambient, ambient +4 °C, and ambient +8 °C) at either 400 ppm or 750 ppm CO2, to simulate climate conditions between now and the year 2100. Spruce acclimated to increasing temperature detractively; warming scenarios reduced spruce net carbon gain. Tamarack maintained comparable levels of net photosynthesis (Anet) across warming treatments and both species acclimated respiration (Rdark) with increasing growth temperature. Elevated CO2-grown spruce suppressed Anet whereas tamarack was insensitive. Decreasing leaf N with warming explained reduced Anet and Rdark for both species; however, tamarack mitigated this by increasing stomatal conductance. Moderate warming benefited tamarack growth but hindered spruce; extreme warming hindered growth in both species. Reduced CO2 uptake in these species with predicted warming may contribute to increased atmospheric CO2 accumulation.

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