Changes in cortical and wood terpenes in Sitka spruce in response to wounding

Abstract

Terpene levels were measured in bark and wood samples of Sitka spruce (Picea sitchensis (Bong.) Carrière) trees. The trees that had been selected as early or late flushing were subjected to artificial wounding to simulate attack by the white pine weevil, Pissodes strobi (Peck). Samples were taken at four times during the growing season: before wounding, shortly after wounding, and two times later in the season. Terpenes were extracted with hexane and quantified by capillary gas chromatography. There were no significant differences in total bark terpenes between early- and late-flushing trees or between control and wounded trees over all sampling times. There were no significant differences in total wood terpenes between early- and late-flushing trees or among sampling times, but a statistically significant difference was found between control and wounded trees. Eleven individual terpenes accounted for the majority of the terpenes in the extracts. Four bark terpenes showed significant differences with sampling time, two with flushing class, and none with treatment. Five wood terpenes showed significant differences with sampling time, two with flushing class, and nine with treatment. We concluded that flushing had only a minor effect on bark and wood terpene profiles and that wounding significantly increased terpene concentration in wood shortly after injury.