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Forty felled dominant and codominant Pacific silver fir trees (Abies amabilis Dougl. ex Forbes) from 39 locations provided the basis for height-age and site index curves. Trees were from upper slope forests of the Cascade Range in Oregon and Washington. Trees ranged in age from 100 to 300 years and were identified by their height-growth trend as free growing throughout their lives. Twenty additional dominant trees with height growth retarded when they were young were excluded from the site index and height-growth analyses. The early rate of diameter growth of these 20 trees was used to develop a general guideline identifying nonfree-growing dominant trees. Equations and height-age curves are presented. A multiple regression equation was developed to express site index (height at age 100) as a function of total tree height and age at breast height. Equations were developed .to estimate the number of years free-growing trees need to reach breast height for the range of site index values. Conversion equations are provided to estimate height at age 50 for curves representing index heights at age 100. The results give forest managers working tools for use in managing silver fir.
Accurate ring counts and radial growth measurements on decayed transverse wood sections are possible when rotted wood is frozen. Technique was successfully used during stem analysis studies of old-growth mixed conifers in the Oregon-Washington Cascade Range.
DeMars, Donald J.; Herman, Francis R. 1987. Estimates of site index and height growth for Douglas-fir in high-elevation forests of the Oregon-Washington Cascade Range: curves and tables for field application. Res. Pap. PNW-RP-378. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 16 p. Estimation equations for height growth and site index were derived from stem-analysis data of Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco var. menziesii) in the highelevation forests of the Cascade Range in Oregon and Washington. Two sets of height-growth and site-index estimation curves and tables produced from previously published equations are presented-one set with U.S. customary units of measure and another set with metric units. These curves and tables were designed for use in the field by forest managers.
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