. Forest mensuration. age, is shown in Fig. 84. By this method (Baurs), thepositions of the maximum and minimum curves determine that of thecurves separating the site qualities. One or two plots with abnormallyrapid or slow growth must not be permitted to influence unduly theposition of these outer curves. With height, the true position of theboundary curves can be found with greater certainty than if volume isused originally as the basis of classification. In this figure, the averageheights of qualities I, II and III at 100 years were taken as 90, 75 and TABLE WITH SITE CLASSES BASED ON HEIGH
. Forest mensuration. age, is shown in Fig. 84. By this method (Baurs), thepositions of the maximum and minimum curves determine that of thecurves separating the site qualities. One or two plots with abnormallyrapid or slow growth must not be permitted to influence unduly theposition of these outer curves. With height, the true position of theboundary curves can be found with greater certainty than if volume isused originally as the basis of classification. In this figure, the averageheights of qualities I, II and III at 100 years were taken as 90, 75 and TABLE WITH SITE CLASSES BASED ON HEIGHT GROWTH 403 60 feet, following the suggestion of Roth as an example of class C inheight classification (Table LV, § 296), and with these guidingpoints the curves limiting the three classes were drawn by Baursmethod. 6. The yield of all plots in a single site class are then plotted oncross-section paper whose base or horizontal scale is age, and whosevertical scale is volume. From these data, a curve of average yield. 100 no 120 130 Years 160 170 180 ISO Fig. 85.—Curves of yield obtained by averaging the yields of plots whose heightgrowth has placed them in the same site class. The final curves smooth offirregularities in these averages. Second growth Western Yellow Pine, B. Show. based on age may be drawn from which the 3delds for the site classfor each decade or five-year period are read. A separate curve is plottedfor each site class. The yield table finally shows the average yieldsbased on age for each separate site class. 404 NORMAL YIELD TABLES FOR EVEN-AGED STANDS When constructed on this basis, yields for different site classesincrease at a greater ratio than do the indicating heights. In drawing the curve of yield based on age for a single site class,it is best to first obtain the average yield for a given decade by arith-metical means and connect these averages by straight lines. Even ifeach plot were normal, the averages at different points
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectforestsandforestry
