Emission of volatile organic compounds from two silver birch ( Roth) clones grown under ambient and elevated CO and different O concentrations

Abstract

Abstract We analysed the emission of volatile organic compounds (VOCs) from two clones (4 and 80) of silver birch ( Betula pendula Roth) trees exposed to doubled ambient CO 2 and O 3 singly and in combination, in open-top chambers. VOCs were collected in July and in August from detached twigs. The effect of twig detachment as such on emissions was separately studied, and it increased the emissions of green leaf volatiles. The emission in July from both clones was dominated by sesquiterpenes (SQTs) germacrene D, ( E,E )- α -farnesene, α -copaene and β -bourbonene, while in August, the emission was dominated by monoterpenes (MTs) ( E )- β -ocimene and ( Z )-ocimene. Elevated CO 2 concentration marginally decreased total MT emission in July, while in August the total MT emission was enhanced by elevated CO 2 . O 3 or CO 2 +O 3 -exposure did not have any effect on total MT or total SQT emissions. In general clones 4 and 80 emitted total quantified VOCs (19 compounds) 12520 and 8590 ng g −1 fw h −1 in July, and 4640 and 4990 ng g −1 fw h −1 in August, respectively. Clone 4 emitted more β -pinene+myrcene, ( Z )-ocimene and ( E )- β -ocimene in July than clone 80, which emitted more linalool in July, and hexanal in August than clone 4. Elevated CO 2 tended to decrease the emissions of nonanal and ( E )- β -ocimene in July, while O 3 and CO 2 +O 3 had no effects on emissions. Our results indicate that elevated CO 2 and O 3 concentrations do not have considerable effect on silver birch emissions by increasing the carbon allocation to VOCs or by inducing the emission of novel compounds. Other factors, such as temperature, light and herbivores might conceal the effects of these atmospheric gases. High SQT proportion in emission profile suggests that B. pendula may have substantial role in biogenic aerosol formation in boreal forests.