. Levels-of-growing-stock cooperative study in douglas-fir. If, at the end of a growth period, attained basal area of a plot was less than the leave basal area calculated as above, no thinning was made on that plot at that thinning date. This situation has occurred occasionally, usually in the highest density treatment. Definition of growing stock levels in terms of observed growth of the control makes growing stock levels specific to the individual installation. There are four fixed- percentage regimes (1, 3, 5, and 7) that retain 10, 30, 50, and 70 percent of control plot gross basal area gr
. Levels-of-growing-stock cooperative study in douglas-fir. If, at the end of a growth period, attained basal area of a plot was less than the leave basal area calculated as above, no thinning was made on that plot at that thinning date. This situation has occurred occasionally, usually in the highest density treatment. Definition of growing stock levels in terms of observed growth of the control makes growing stock levels specific to the individual installation. There are four fixed- percentage regimes (1, 3, 5, and 7) that retain 10, 30, 50, and 70 percent of control plot gross basal area growth; two regimes (2 and 4) that retain successively increasing percentages of control plot growth over successive periods; and two regimes (6 and 8) that retain decreasing percentages of control plot growth. These are referred to in later discussion as "fixed" treatments, 1, 3, 5 and 7; and "variable" treatments consisting of "increasing" treatments, 2 and 4, and "decreasing" treatments, 6 and 8. The pattern of growing stock levels expected as the stand develops is schematically illustrated in figure 2. Treatment regimes will show the same pattern and relative position in each of the studies, although numerical stocking levels for a given treatment vary somewhat among installations because of differences in initial conditions and in control plot growth. Stand condition after the calibration cut is illustrated by figure 3 and that near the end of the planned experiment by figure 4. 01 ED. %> Height Figure 2.—Idealized trends of basal area for the eight thinning 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 Curtis, Robert O. cn; Marshall, David D. cn; Pacific Northwest Research Station (Portland, Or. ) cn. [Portland, Or. ] : U. S. Dept. of Agriculture,
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