Southern Research Station

Title: Growth and crown architecture of two aspen genotypes exposed to interacting ozone and carbon dioxide

Author: Dickson, Richard E.; Coleman, M.D.; Pechter, Priit; Karnosky, David

Date: 2001

Source: Environmental Pollution 115 (2001) 319-334

Description: To study the impact of ozone (O₃) and O₃ plus CO₂ on aspen growth, we planted two trembling aspen clones, differing in sensitivity to O3, in the ground in open-top chambers and exposed them to different concentrations of O₃ and O₃ plus CO₂ for 98 days. Ozone exposure (58 to 97 µl1^-1-h, total exposure) decreased growth and modified crown architecture of both aspen clones. Ozone exposure decreased leaf, stem, branch, and root dry weight particularly in the O₃ sensitive clone (clone 259). The addition of CO₂ (150 µl1^-1 over ambient) to the O₃ exposure counteracted the negative impact of O₃ only in the O3 tolerant clone (clone 216). Ozone had relatively little effect on allometric ratios such as, shoot/ root ratio, leaf weight ratio, or root weight ratio. In both clones, however, O₃ decreased the shoot dry weight/shoot length ratio and shoot diameter. This decrease in wood strength caused both current terminals and long shoots to droop and increased the branch angle of termination. These results show that aspen growth is highly sensitive to O₃ and that O₃ can also significantly affect crown architecture. Aspen plants with drooping terminals and lateral branches would be at a competitive disadvantage in dense stands with limited light.

Keywords: Populus tremuloides, Ozone exposure, Elevated CO₂, Crown architecture, Genotypic response

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Citation

Dickson, Richard E.; Coleman, M.D.; Pechter, Priit; Karnosky, David  2001.  Growth and crown architecture of two aspen genotypes exposed to interacting ozone and carbon dioxide.   Environmental Pollution 115 (2001) 319-334