Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/19/2011
Publication Date: 5/3/2011
Citation: Wallis, C.M., Huber, D.P., Lewis, K.J. 2011. Ecosystem, location, and climate effects on foliar secondary metabolites of lodgepole pine populations from central British Columbia. Journal of Chemical Ecology. 37(6):607-621. Interpretive Summary: Many lodgepole pine (Pinus contorta latifolia) populations are stressed due to recent increases in temperature and changes in precipitation patterns. One way pines counter abiotic and biotic stresses is by producing secondary metabolites, which are host-produced compounds (including phenolics and terpenes) that are not directly involved in growth or reproduction. Secondary metabolites were examined in pine foliage in 13 stands spread throughout British Columbia, Canada. Lodgepole pine populations growing in different ecosystems possessed significantly different secondary metabolites levels, with most phenolics and terpene levels highest in stands closest to the Pacific. Lignin levels were significantly higher in the northernmost stands, perhaps because this phenolic polymer is involved in cold-hardiness. Attempts were also made to correlate historical stand temperature and precipitation means with secondary metabolite levels. Both temperature and precipitation means were positively associated with foliar monoterpene and sesquiterpene levels, and temperature means were positively associated with phenolic levels. Thus, lodgepole pines could have adapted to growing in different ecosystems and climates by adjusting their foliar secondary metabolite levels. Whether or not the differences in secondary metabolite profiles between stands is a result of different genetic potential or phenotypic plasticity remains unclear, and requires additional study. Results from this study will provide forest managers with knowledge about which pine populations might be best suited for replanting efforts in different locations.
Technical Abstract: Lodgepole pines (Pinus contorta Douglas ex Louden var. latifolia Engelm. ex S. Watson) are encountering increased abiotic stress and pest activity due to recent increases in temperature and changes in precipitation throughout their range. Pines counter these threats by producing secondary metabolites, including phenolics and terpenes. This work examined foliar levels of lignin, soluble phenolics, monoterpenes, sesquiterpenes, and diterpenes in 13 lodgepole pine stands in British Columbia, Canada. This data was used to assess association between secondary metabolite levels with ecosystem and climatic variables. Pine stands in closest geographical proximity to the Pacific (those consisting of the shore pine variation of Pinus contorta (var. contorta) or lodgepole pines in the Coastal Western Hemlock and Interior Cedar/Hemlock biogeoclimatic zones) had consistently greater foliar levels of almost all measured secondary metabolites than did more easterly stands. Lignin was present in greater amounts in northern stands than in southern stands, suggesting a role in cold-hardiness. Temperature appeared to be more important than precipitation in affecting levels of secondary metabolites, with warmer summer and annual temperatures consistently resulting in greater levels of all terpenoids, and colder summer temperatures resulting in greater foliar lignin. Annual precipitation was positively associated with monoterpene and sesquiterpene levels. Foliar secondary metabolite levels varied among lodgepole pine stands, suggesting that metabolic profiles are matched to local environments. It is unknown if differences in secondary metabolite levels are the result of genetic adaptation or phenotypic plasticity, but results from this and other studies suggest that both are likely to be important.