Abstract
Abstract. Monoterpene emissions from Scots pine have traditionally been assumed to originate as evaporation from specialized storage pools. More recently, the significance of de novo emissions, originating directly from monoterpene biosynthesis, has been recognized. To study the role of biosynthesis at the ecosystem scale, we measured monoterpene emissions from a Scots pine dominated forest in southern Finland using the disjunct eddy covariance method combined with proton transfer reaction mass spectrometry. The interpretation of the measurements was based on a correlation analysis and a hybrid emission algorithm describing both de novo and pool emissions. During the measurement period May–August 2007, the monthly medians of daytime emissions were 200, 290, 180, and 200 μg m−2 h−1. The emissions were partly light dependent, probably due to de novo biosynthesis. The emission potential for both de novo and pool emissions exhibited a decreasing summertime trend. The ratio of the de novo emission potential to the total emission potential varied between 30 % and 46 %. Although the monthly changes were not significant, the ratio always differed statistically from zero, suggesting that the role of de novo biosynthesis was observable. Given the uncertainties in this study, we conclude that more accurate estimates of the contribution of de novo emissions are required for improving monoterpene emission algorithms for Scots pine dominated forests.
Highlights
Monoterpenes are estimated to be major contributors to aerosol particle formation and growth (e.g. Tunved et al, 2006; Hallquist et al, 2009), often cited as the key uncertainty in current climate change research
To study the role of biosynthesis at the ecosystem scale, we measured monoterpene emissions from a Scots pine dominated forest in southern Finland using the disjunct eddy covariance method combined with proton transfer reaction mass spectrometry
Our analysis based on the disjunct eddy covariance method (DEC) measurements above a boreal Scots pine dominated forest revealed five features of the ecosystem scale monoterpene emissions
Summary
Monoterpenes are estimated to be major contributors to aerosol particle formation and growth (e.g. Tunved et al, 2006; Hallquist et al, 2009), often cited as the key uncertainty in current climate change research. The disjunct eddy covariance method (DEC; Rinne et al, 2001; Karl et al, 2002) has been widely applied to volatile organic compound (VOC) flux measurements at the ecosystem scale. It has usually been combined with proton transfer reaction mass spectrometry (PTR-MS), which is an online technique for measuring VOC concentrations (Lindinger et al, 1998; de Gouw and Warneke, 2007; Blake et al, 2009). This combination has yielded fundamental information on VOC emissions from various ecosystems (e.g. Warneke et al, 2002; Spirig et al, 2005; Holzinger et al, 2006; Brunner et al, 2007; Rinne et al, 2007; Davison et al, 2009; Bamberger et al, 2010; Holst et al, 2010; Langford et al, 2010; Misztal et al, 2010)
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