Wednesday, August 8, 2007

PS 50-161: Field measurements of stem respiration in three clones of Populus tremuloides subjected to elevated carbon dioxide and ozone fumigation in a FACE experiment

John Hom1, Steve Roberts2, and Matthew Patterson1. (1) USDA Forest Service, (2) Data Design Group

Stem respiration measurements by carbon dioxide efflux were carried out in three aspen (Populus tremuloides Michx.) clones subjected to elevated carbon dioxide and ozone treatments, separately and in combination, using an automated multi-cuvette system at the USDA-FS Harshaw Experimental Forest research station near Rhinelander WI. In all three clones, mean nighttime respiration and daily total net carbon loss increased in stems subjected to CO2 fumigation (1.64 umol CO2/m2/s, 1.93 grams C/m2/d) compared to non-fumigated control stems (1.27 umol CO2/m2/s, 1.45 grams C/m2/d). Stems subjected to O3 alone showed the lowest dark respiration maxima (0.87 umol/m2/s) and the least respiration sensitivity (Q10) to temperature (1.90). Adding CO2 to the O3 treatment (combined CO2+O3) increased both the nighttime respiration maxima (1.20 umol/m2/s) and the temperature sensitivity (2.47), compared to O3 alone. The overall mean  temperature sensitivities of stem respiration, as indicated by Q10 values, were variable, dependent on experimental treatment, and ranged from 1.8 to 3.0, similar to the range of values reported for other Populus species.  

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