| The volatile organic compound (VOC) emission rates of Scots pine
(Pinus sylvestris L.) were measured from trees growing in a
natural forest environment at two locations in Finland. The observed
total VOC emission rates varied between 21 and
874 ngg-1 h-1 and 268 and
1670 ngg-1 h-1 in southern and northern Finland,
respectively. A clear seasonal cycle was detected with high emission
rates in early spring, a decrease of the emissions in late spring
and early summer, high emissions again in late summer, and a gradual
decrease in autumn.
The main emitted compounds were Δ3-carene (southern Finland)
and α- and β-pinene (northern Finland), with approximate
relative contributions of 60–70% and 60–85% of the total observed
monoterpene emission rates, respectively. Sesquiterpene (β-caryophyllene) and 2-methyl-3-buten-2-ol (MBO) emissions were initiated in
early summer at both sites. The observed MBO emission rates were between 1
and 3.5% of the total monoterpene emission rates. The sesquiterpene
emission rates varied between 2 and 5% of the total monoterpene emission
rates in southern Finland, but were high (40%) in northern Finland in
spring.
Most of the measured emission rates were found to be well described
by the temperature dependent emission algorithm. The calculated
standard emission potentials were high in spring and early summer,
decreased somewhat in late summer, and were high again towards
autumn. The experimental coefficient β ranged from 0.025 to
0.19 (average 0.10) in southern Finland, with strongest temperature
dependence in spring and weakest in late summer. Only the emission
rates of 1,8-cineole were found to be both light and temperature
dependent. |