Variation in sapwood area -- leaf area relations within two stands oflodgepole pine

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For. Sci.



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Within-stand variation of the ratio between sapwood cross-sectional area and leaf area was investigated for lodgepole pine (Pinus contorta Dougl.) in northern Utah. For both a mature and a sapling stand, we analyzed the changes in sapwood-leaf area ratio with respect to canopy position and location along the bole, both within and below the live crown.

Excluding suppressed trees, sapwood area at the base of the live crown (BLC) was linearly related to leaf area; however, the slope of the regression for the saplings was 40% greater than the slope for the mature trees. This difference was virtually eliminated when sapwood area at BLC was related to a power function of leaf area for all crown classes. Sapwood area increased from the base of the crown to the base of the crown-free bole. For the mature and sapling trees 98% and 91%, respectively, of the variation in sapwood below the live crown was explained using nonlinear regression with the model

SA = β0(L·LA)β¹

where SA = any sapwood cross-sectional area below the live crown, L = distance from the cross section to midway into crown or center of leaf area, LA = total leaf area per tree, and β0 and β1 = regression coefficients. The sapwood-leaf area ratio varied within the crowns of the mature and sapling trees; the maximum ratio occurred toward the base and the top of the crown and the minimum ratio was found at about the center of leaf area. Forest Sci. 32:749-758.