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STOMATAL RESPONSES OF DOUGLAS-FIR SEEDLINGS TO ELEVATED CARBON DIOXIDE AND TEMPERATURE DURING THE THIRD AND FOURTH YEARS OF EXPOSURE
Citation:
Lewis, J. D., M. Lucash, D M. Olszyk, AND D T. Tingey. STOMATAL RESPONSES OF DOUGLAS-FIR SEEDLINGS TO ELEVATED CARBON DIOXIDE AND TEMPERATURE DURING THE THIRD AND FOURTH YEARS OF EXPOSURE. PLANT, CELL, AND ENVIRONMENT. Blackwell Publishing, Malden, MA, 25:1411-1421.
Description:
Two major components of climate change, increasing atmospheric [CO2] and increasing temperature, may substantially alter the effects of water availability to plants through effects on the rate of water loss from leaves. We examined the interactive effects of elevated [CO2] and temperature on seasonal patterns of stomatal conductance, transpiration and instantaneous transpiration efficiency (ITE; mmoles CO2 assimilated per mole H2O transpired) in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings. Seedlings were grown in sunlit chambers at either ambient CO2 or ambient + 180 mol mol-1 CO2, and at ambient temperature or ambient + 3.5 ?C. Needle gas exchange at the growth conditions was measured approximately monthly over 21 months. Across the study period, growth in elevated [CO2] decreased transpiration rates an average of 12% and increased ITE an average of 46%. The absolute reduction of transpiration rates associated with elevated [CO2] significantly increased with seasonal increases in vapour pressure deficit (VPD). Growth in elevated temperature increased transpiration rates an average of 37%, and did not affect ITE. Combined, growth in elevated [CO2] and elevated temperature increased transpiration rates an average of 19% compared to growth in ambient conditions. Stomatal sensitivity to VPD did not significantly vary between CO2 or temperature treatments. This study suggests that climate change may substantially alter needle-level water loss and water use efficiency of Douglas-fir, but will not change stomatal sensitivity to VPD.