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Allometry of Phloem Thickness and Resin Flow and Their Relation to Tree Chemotype in a Southwestern Ponderosa Pine Forest

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We measured traits of 470 Pinus ponderosa in northern Arizona and constructed equations scaling phloem thickness and resin flow to tree size. We tested the hypothesis that these traits were related to tree monoterpene chemotype. The monoterpene composition of resin was analyzed for a subset of trees ( n = 146). Correlation analyses revealed that all tree phenotypic traits were positively correlated. Equations of phloem thickness and resin flow were nonlinear: phloem thickness was a logarithmic function of tree diameter, and diameter explained moderate variation in phloem thickness ( R 2 = 0.234). Similarly, resin flow was a reciprocal function of diameter ( R 2 = 0.214). Resin flow rapidly increased with tree diameter but plateaued as tree diameter exceeded 40 cm. Phloem thickness was only weakly linearly related to resin flow ( R 2 = 0.078). A multivariate regression incorporating diameter, height, and phloem thickness did not explain substantially more variance in resin flow than diameter alone. We found no evidence to suggest that tree phenotype was related to tree chemotype. We conclude that there are positive but weak relationships between tree size, phloem thickness, and resin flow in southwestern ponderosa pine and that trees with thick phloem are not necessarily better defended from herbivory by resin flow.

Keywords: conifer; oleoresin; terpenoids; tree traits; vascular tissue

Document Type: Research Article


Publication date: 2014-04-01

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  • Forest Science is a peer-reviewed journal publishing fundamental and applied research that explores all aspects of natural and social sciences as they apply to the function and management of the forested ecosystems of the world. Topics include silviculture, forest management, biometrics, economics, entomology & pathology, fire & fuels management, forest ecology, genetics & tree improvement, geospatial technologies, harvesting & utilization, landscape ecology, operations research, forest policy, physiology, recreation, social sciences, soils & hydrology, and wildlife management.
    Forest Science is published bimonthly in February, April, June, August, October, and December.

    2015 Impact Factor: 1.702
    Ranking: 16 of 66 in forestry

    Average time from submission to first decision: 62.5 days*
    June 1, 2016 to Feb. 28, 2017

    Also published by SAF:
    Journal of Forestry
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