Monoterpene emissions from Scots pine (Pinus sylvestris): Field studies of emission rate variabilities

Abstract

Monoterpene emission rates from young and adult Scots pines (Pinus sylvestris), a typical central European conifer, were measured under ambient conditions using a dynamic enclosure chamber. We investigated diurnal and seasonal cycles of monoterpene emissions and branch‐to‐branch and plant‐to‐plant variabilities of emission rates. The four most abundant monoterpenes usually emitted from Pinus sylvestris were α‐pinene, 3‐carene, camphene, and β‐pinene. Emissions of individual monoterpenes were highly correlated to each other and increased exponentially with temperature. We obtained β coefficients for the temperature dependence of different monoterpenes between 0.08 and 0.13 K−1. The β coefficients varied with season by a factor of 2; the standard emission rates varied by more than 1 order of magnitude. Highest standard emission rates were found in April; lowest standard emission rates were found in July and October. In July and October the standard emission rates from two different branches of the same tree showed no significant differences; in September they differed by a factor of 2. Seasonal variations of a single branch and branch‐to‐branch variations in the spectrum of emitted monoterpenes were small. On the other hand, different individual Scots pines emitted a completely different spectrum of monoterpenes, indicating that the monoterpene emission spectrum is only typical for an individual plant but not for the whole plant species. The temperature normalized standard emission rates were found to be highly variable. Values for the sum of monoterpenes ranged between 0.06 and 3.7 μg g(dry weight)−1 h−1 (micrograms monoterpenes per gram dry weight (dw) of needles and hour). Temperature‐normalized monoterpene emission rates and temperature dependencies of the emissions were used to calculate monthly flux estimates of monoterpenes for the Hartheimer Wald.