. Site index and height growth curves for unmanaged even-aged stands of western hemlock and sitka spruce in southeast Alaska. Western hemlock Alaska; Sitka spruce Alaska; Forest management Alaska; Site index (Forestry) Alaska. Figure 6 —bi values for western hemlock in the equa- tion (S - feet) = a, + b, (HT — feet) as a function of age. Plotted points are actual b, values. Solid line is expressed by the equation bi = e*1. Coefficient xi is defined in the text. Standard error is and r2 is r- 20 40 60 100 120 140 160 Age at breast height (years) Coeffici
. Site index and height growth curves for unmanaged even-aged stands of western hemlock and sitka spruce in southeast Alaska. Western hemlock Alaska; Sitka spruce Alaska; Forest management Alaska; Site index (Forestry) Alaska. Figure 6 —bi values for western hemlock in the equa- tion (S - feet) = a, + b, (HT — feet) as a function of age. Plotted points are actual b, values. Solid line is expressed by the equation bi = e*1. Coefficient xi is defined in the text. Standard error is and r2 is r- 20 40 60 100 120 140 160 Age at breast height (years) Coefficient bi turned sharply downward at age 150. Because the logarithmic equation (using natural logs) is very sensitive, the regression curve also turned sharply downward beyond age 140 years. To correct for this, the data were smoothed to remove extreme variation in bi over age at ages 140 to 150 years. The derived equation was: x^ = loge(bi) = - + (logeage) - (logeage)2 + X 10"6 (logeage)8 - X 10~9 (logeage)12 + X 10-27 (logeage)36; where: age = age at breast height. Mean height for each 10-year age at breast height was also calculated and plotted (table 6 and fig. 7). Number of plots and mean site index in each decadal age decreased beyond age 50 years, so mean height at each decadal age beyond age 50 did not represent the height corresponding to mean site index at age 50 years (). Heights were therefore adjusted by use of the Ci and di coefficients for each age class and mean site index at age 50 in the equation, HT = + Ci + di ( - ). 15. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Farr, Wilbur A. cn; Pacific Northwest Forest and Range Experiment Station (Portland, Or. ) cn. [Portland, Or. ] : U. S. Dept. of Agriculture, For
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