European Geosciences Union, Biogeosciences Discussions, 10(12), p. 7783-7814
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Tree canopies are known to emit large amounts of VOCs (volatile organic compounds) such as monoterpenes to the surrounding air. The main source for these is considered to be the green biomass, i.e. foliage, but emissions from the woody compartments have not been quantified. A VOC emission anomaly has been observed during transition from winter to summer activity. We analyzed if non-foliar components could partially explain the anomaly. We measured the VOC emissions from Scots pine ( Pinus sylvestris L.) stems and shoots during the dehardening phase of trees in field conditions in two consecutive springs. We observed a large, transient monoterpene burst from stems, while the shoot monoterpene emissions and transpiration remained low. The burst lasted about 12 h. Simultaneously, an unusual night-time sap flow and an anomalous diurnal pattern of tree diameter were detected. Hence, we suggest that the monoterpene burst was a consequence of the recovery of the stem from winter-time. This indicates that the dominant processes and environmental drivers triggering the monoterpene emissions are different between stems and foliage.