Journal
TREE PHYSIOLOGY
Volume 28, Issue 2, Pages 243-254Publisher
OXFORD UNIV PRESS
DOI: 10.1093/treephys/28.2.243
Keywords
bud burst; bud carbohydrates; bud size; gas exchange; leaf abscission; leaf area index; leaf size; paper birch; phenology; photosynthesis; trembling aspen
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Paper birch (Betula papyrifera Marsh.) and three trembling aspen clones (Populus tremuloides Michx.) were studied to determine if alterations in carbon gain in response to an elevated concentration of CO2 ([CO2]) or 03 ([03]) or a combination of both affected bud size and carbohydrate composition in autumn, and early leaf development in the following spring. The trees were measured for gas exchange, leaf size, date of leaf abscission, size and biochemical characteristics of the overwintering buds and early leaf development during the 8th-9th year of free-air CO2 and O-3 exposure at the Aspen FACE site located near Rhinelander, WI. Net photosynthesis was enhanced 49-73% by elevated [CO2], and decreased 13-30% by elevated [O-3]. Elevated [CO2] delayed, and elevated [O-3] tended to accelerate, leaf abscission in autumn. Elevated [CO2] increased the ratio of monosaccharides to di- and oligosaccharides in aspen buds, which may indicate a lag in cold acclimation. The total carbon concentration in overwintering buds was unaffected by the treatments, although elevated [O-3] decreased the amount of starch by 16% in birch buds, and reduced the size of aspen buds, which may be related to the delayed leaf development in aspen during the spring. Elevated [CO2] generally ameliorated the effects of elevated [O-3]. Our results show that both elevated [CO2] and elevated [O-3] have the potential to alter carbon metabolism of overwintering buds. These changes may cause carry-over effects during the next growing season.
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