This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 798293
BIOVOLHUM
An understated player of Climate Change - increased air humidity - impact on volatile signaling compound emission at northern forests
Global climate scenarios predict that in northern regions climate will be wetter with higher rates of precipitation. However, the accuracy of those predictions is quite low, because we have very vague knowledge of the effect of forest canopies on future climate. Forests emit highly reactive particles (volatile organic compounds – VOC and nitric oxides - NOx) which play an important role in cloud formation above forests. The formation of clouds is not merely important because of increased precipitation probability, but also because the more there will be cloudy days, the less amount of an essential resource – sunlight - reaches the vegetation. In fact, just as atmospheric properties (temperature and humidity) affect the emissions of those reactive particles, reactive particles in turn affect atmospheric properties as well. In order to make any assumptions of how cloudy and humid future climate in north will be, we need to understand, how climate affects the emissions of different reactive particles from northern forests.
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AIMS
Our aim was to understand, how increased air humidity and soil moisture affects the emissions of reactive volatile compounds from canopies of silver birches (a very common tree species in northern Europe). We did not only look at the changes in reactive compound emissions, that are directly related with higher moisture conditions, but we also investigated, how wet climate indirectly affects the physiology of birches and thus also affects the production of volatile reactive compounds.
Special interest of this project was to reveal, if the inability of plants to use produced sugars for growth due to non-optimal humidity conditions, might increase the emissions of carbon containing reactive particles as carbon is in excess.
METHODS
Reactive compound emissions from silver birches were measured at a unique experimental site FAHM (in Estonia), where air humidity is artificially increased in an open-air setting at planted forest plots. Measurements were done in three control plots and three plots, where air was artificially increased.
In order to measure volatile organic compound (VOC) emissions exclusively from birch shoots, we pumped standard air through shoot-chambers and absorbed VOC into tenax tubes. Additionally also climate factors and different parameters, describing plant physiological characteristics, were measured.
WHA DID WE FIND?
We found that more moist climate produces significant changes in the ratio of different reactive compounds that are emitted into the atmosphere by birch forests. The effect of more humid birch forest on composition of atmosphere in future might depend also on the rate of non-structural carbohydrate ( Ì´ sugars) accumulation within trees due to the climatic changes as emissions of monoterpenes and sesquiterpenes are differently affected by the latter.
CONTACT:
Pille Mänd
Department of Forest Sciences, P.O. Box 27, 00014, University of Helsinki, Helsinki, Finland
