Canopy scale monoterpene emissions of Pinus sylvestris dominated forests

Canopy scale monoterpene emissions were measured using the micrometeorologi cal gradient method at two sites, Huhus and Hyytiala, in the European borea l zone. At both sites the dominant tree species was Pinus sylvestris. The d ominant monoterpene emitted by the forests was alpha-pinene, followed by De lta(3)-carene and beta-pinene/myrcene. At the more homogenous Huhus site mo noterpene emission correlated reasonably well with the IR-temperature of th e canopy and the air temperature inside the canopy, and the common exponent ial equation could be used to describe the emissions. The beta-coefficient obtained was 0.15 degrees C-1, which is somewhat higher than the commonly u sed value of 0.09 degrees C-1. The emission potential calculated using the measured canopy scale emissions and beta = 0.09 degrees C-1 was 1.2 mu g g( dw)(-1) h(-1) which is close to 1.5 mu g g(dw)(-1) h(-1) used in recent emi ssion inventories. The measured emissions at the more heterogeneous Hyytial a site were not well correlated with the meteorological parameters. However , the coefficients obtained using the Huhus measurements predicted the magn itude of the fluxes measured at Hyytiala reasonably well. (C) 2000 Elsevier Science Ltd. All rights reserved.