. Growth of ponderosa pine poles thinned to different stocking levels in central Oregon. Ponderosa pine Oregon; Ponderosa pine Oregon Spacing. Ill Q. c c <" - Five-year growth period [J First ] Second [I Third lilt 30 2 12 15 5 7 10 Plot number 80 100 Growing-stock level 13 14 17 120 Figure 3.—Periodic, annual growth in diameter of ponderosa pine poles thinned to six different growing-stock levels on a productive site in central Oregon. Five-year growth period. 6 11 18 3 8 16 2 12 15 5 7 10 4 9 13 1 14 17 Plot number 30 60 80 100 120 150 Growing-
. Growth of ponderosa pine poles thinned to different stocking levels in central Oregon. Ponderosa pine Oregon; Ponderosa pine Oregon Spacing. Ill Q. c c <" - Five-year growth period [J First ] Second [I Third lilt 30 2 12 15 5 7 10 Plot number 80 100 Growing-stock level 13 14 17 120 Figure 3.—Periodic, annual growth in diameter of ponderosa pine poles thinned to six different growing-stock levels on a productive site in central Oregon. Five-year growth period. 6 11 18 3 8 16 2 12 15 5 7 10 4 9 13 1 14 17 Plot number 30 60 80 100 120 150 Growing-stock level Figure 4.—Periodic, annual basal-area incre- ment of ponderosa pine poles thinned to six different growing-stock levels on a productive site in central Oregon. Significant differences in net basal-area increment were observed only in the second growth period, but net differences are not very useful or meaningful because of the erratic nature of mortality. Only 5 of the 18 plots had losses in basal area that exceeded 10 percent of gross growth. Two of the five occurred in GSL150 plots. No losses in basal area occurred in the GSL 30 plots. Height—Attempts to detect differences in height growth between growing-stock levels was difficult because of the limited sample of heights (15 per plot) and the within-treatment variation encountered. Analysis of variance with the data avail- able indicated no significant differences in height growth between GSL's. Volume—Periodic growth in total stem volume was strongly related to growing- stock level throughout all periods (fig. 5). Net growth was adversely affected by mortality on some plots, especially during the last period. GSL 100 was a poor producer during the first period in all replications, for some reason. Increment consistently rose from the first 5-year period to the second in all plots and then dropped consistently in the third period after the second thinning. Growth dropped even on plot 9, which was not thin
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