Canopy scale monoterpene emissions of Pinus sylvestris dominated forests

Canopy scale monoterpene emissions were measured using the micrometeorological gradient method at two sites, Huhus and Hyytiala, in the European boreal zone. At both sites the dominant tree species was Pinus sylvestris. The dominant monoterpene emitted by the forests was alpha-pinene, followed by Delta(3)-carene and beta-pinene/myrcene. At the more homogenous Huhus site monoterpene emission correlated reasonably well with the IR-temperature of the canopy and the air temperature inside the canopy, and the common exponential 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 used 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 emission inventories. The measured emissions at the more heterogeneous Hyytiala site were not well correlated with the meteorological parameters. However, the coefficients obtained using the Huhus measurements predicted the magnitude of the fluxes measured at Hyytiala reasonably well. (C) 2000 Elsevier Science Ltd. All rights reserved.