Journal Article

Regulation of ponderosa pine foliar physiology and insect resistance mechanisms by basal area treatments

Thomas E. Kolb, Kristina M. Holmberg, Michael R. Wagner and Joseph E. Stone

in Tree Physiology

Volume 18, issue 6, pages 375-381
Published in print June 1998 | ISSN: 0829-318X
Published online June 1998 | e-ISSN: 1758-4469 | DOI: http://dx.doi.org/10.1093/treephys/18.6.375
Regulation of ponderosa pine foliar physiology and insect resistance mechanisms by basal area treatments

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We compared foliar physiology and several measures of tree resistance to insect attack among ponderosa pine (Pinus ponderosa var. scopulorum Engelm.) trees growing in thinned stands. Measurements were made in a second-growth ponderosa pine forest in northern Arizona where the basal area treatments (6.9, 18.4, 27.6, 78.2 m2 ha−1) have been experimentally maintained by frequent thinnings for 32 years before our measurements began in 1994. Most of the physiological characteristics measured were affected by the basal area treatments. As stand basal area increased from 6.9 to 78.2 m2 ha−1, predawn water potential, midday water potential, net photosynthetic rate, resin production, phloem thickness, and foliar toughness decreased. Foliar nitrogen concentration was greatest in trees in the intermediate basal area treatments. Our results show that the physiological condition of second-growth ponderosa pine can be manipulated by silvicultural control of stand basal area, and support the hypothesis that high stand basal area increases tree stress and decreases tree resistance to insect attack.

Keywords: Arizona; foliar toughness; herbivory; phloem thickness; photosynthesis; Pinus ponderosa; resin; thinning; water relations

Journal Article.  0 words. 

Subjects: Plant Sciences and Forestry

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