title: Monoterpene emissions in response to long-term night-time warming, elevated CO2and extended summer drought in a temperate heath ecosystem.
abstract: Monoterpenes emitted from plants have an important role in atmospheric chemistry through changing atmospheric oxidative capacity, forming new particles and secondary organic aerosols. The emission rates and patterns can be affected by changing climate. In this study, emission responses to six years of climatic manipulations (elevated CO2, extended summer drought and night-time warming) were investigated in a temperate semi-natural heath ecosystem. Samples for monoterpene analysis were collected in seven campaigns during an entire growing season (April-November, 2011). The results showed that the temperate heath ecosystem was a considerable source of monoterpenes to the atmosphere, with the emission averaged over the 8month measurement period of 21.7±6.8μgm-2groundareah-1for the untreated heath. Altogether, 16 monoterpenes were detected, of which the most abundant were α-pinene, δ-3-carene and limonene. The emissions of these three compounds were positively correlated with light, chamber temperature and litter abundance, but negatively correlated with soil temperature. Elevated CO2tended to decrease the average monoterpene emissions by 40% over the whole growing season, and significantly reduced emissions in August. Extended summer drought significantly decreased the emission right after the drought treatment period, but also in the late growing season. Night-time warming significantly increased the total emissions (mainly α-pinene) in April, and tended to mitigate the decrease caused by drought. The inhibition effects of elevated CO2on emissions were diminished when the treatment was combined with drought or warming. The emission responses to different treatments were not explained by vegetation changes, and the monoterpene emission profile was only moderately related to plant species coverage. The emission responses to these long-term climate manipulations varied over the growing season (with strong correlation with litter abundance) and the observed antagonistic effects in the combined treatments underlie the importance of long-term studies with multiple factors acting in concert.
authors.affiliation: Department of Environmental and Biological Sciences, University of Eastern Finland, Kuopio Campus, PO Box 1627, FI-70211 Kuopio, Finland. Electronic address: paivi.tiiva@uef.fi.
authors.forename: Päivi
authors.initials: P
authors.lastname: Tiiva
authors.affiliation: Terrestrial Ecology Section, Department of Biology, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen Ø, Denmark; Center for Permafrost (CENPERM), University of Copenhagen, Øester Voldgade 10, DK-1350 Copenhagen K, Denmark. Electronic address: jing.tang@bio.ku.dk.
authors.forename: Jing
authors.initials: J
authors.lastname: Tang
authors.affiliation: Terrestrial Ecology Section, Department of Biology, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen Ø, Denmark; Center for Permafrost (CENPERM), University of Copenhagen, Øester Voldgade 10, DK-1350 Copenhagen K, Denmark. Electronic address: andersm@bio.ku.dk.
authors.forename: Anders
authors.initials: A
authors.lastname: Michelsen
authors.affiliation: Terrestrial Ecology Section, Department of Biology, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen Ø, Denmark; Center for Permafrost (CENPERM), University of Copenhagen, Øester Voldgade 10, DK-1350 Copenhagen K, Denmark. Electronic address: riikkar@bio.ku.dk.
authors.forename: Riikka
authors.initials: R
authors.lastname: Rinnan
mesh_terms: D002245:Carbon Dioxide; D003718:Denmark; D055864:Droughts; D017753:Ecosystem; D039821:Monoterpenes / Q000032:analysis*; D018515:Plant Leaves; D010944:Plants; D012621:Seasons; D013696:Temperature
chemical_list: D039821:Monoterpenes; D002245:Carbon Dioxide
keywords: Antagonistic effect; Biogenic volatile organic compound; Calluna vulgaris; Climate manipulation; FACE; Vegetation change