Impact of diffuse light on isoprene and monoterpene emissions from amixed temperate forest
Earth and related Environmental sciences
Low temperature production
proton transfer reaction mass spectrometry
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This study investigated the impact of diffuse light on canopy scale emission of isoprene and monoterpenes measured continuously above a mixed temperate forest, using the disjunct eddy-covariance by mass scanning technique with a proton transfer reaction-mass spectrometer (PTR-MS) instrument. To assess this impact, the relationship between emissions/radiation and emissions/gross primary production (GPP) under clear sky and cloudy conditions were analysed. Under cloudy conditions (high proportion of diffuse radiation), the isoprene and monoterpene fluxes were enhanced compared to clear sky conditions (low proportion of diffuse radiation) at equivalent temperature and above-canopy total radiation. The whole-canopy enzymatic activity of the metabolic isoprene production pathway, however, was suggested to be lower under cloudy conditions than under clear sky conditions at equivalent temperature. The mechanisms behind these observations are probably linked to the better penetration of diffuse radiation in the canopy. Shade leaves/needles receive more radiation in cloudy conditions than in clear sky conditions, thereby inducing the observed effects.
CitationLaffineur, Q.; Aubinet, M.; Schoon, N.; Amelynck, C.; Muller, J.-F.; Dewulf, J.; Steppe, K.; Heinesch, B. (2013). Impact of diffuse light on isoprene and monoterpene emissions from amixed temperate forest. , Atmospheric Environment, Vol. 74, 385-392, DOI: 10.1016/j.atmosenv.2013.04.025.