LITERATURE CITED Brackett, Michael. 1973. Notes on tarif tree volume computation. Resour. Manage. Rep. 24, 26 p. Wash. State Dep. Natur. Resour., Olympia. Bruce, David, and Donald J. DeMars. Curtis, Robert O., and Donald 1970. Crown development and Eversole, Kenneth R. Reukema, Donald L. 1959. Some recent development Reukema, Donald L. 1970. Forty-year development of Douglas-fir stands planted at various spacings. USDA For. Serv. Res. Pap. PNW-100, 21 p. Pac. Northwest For. and Range Exp. Stn., Portland, Oreg. Reukema, Donald L. Guidelines for precom- Reukema, Donald L., and 1977. Effects of thinning on 1967. The influence of spacing APPENDIX Fitted Curves Trend curves illustrate what I believe to be reasonable approximations of effects of spacing, in the absence of other sources of variation. Equations were fitted to selected plots to facilitate automation in plotting graphs. Most of these relationships are represented by third-degree curves, which closely approximate former freehand curves. For this purpose, 7 of the 18 plots were excluded from influencing the shape of these curves, because inclusion of all plots would result in unrealistic curve shapes. Three of these plots sample the 8-foot spacing, which is apparently on generally poorer-quality site than the average; only the best plot in this spacing (plot 17) falls in line with general trends. Others excluded were the best of the plots at 4- and 10-foot spacings (plots 1 and 14), which are apparently on better-quality site than any other plots, and the poorest of the plots at 5- and 6-foot spacings (plots 4 and 8), which are much poorer than other plots at these spacings. Adjustments for Plot Size Because dimensions of plots-e.g., 104.36 feet for a square quarter-acre plot--are not exact multiples of spacing distances, some plots have either more or fewer planting spots than would theoretically be found on that fraction of an acre. Therefore, the expansion factor to an acre basis has always been derived from an adjusted plot size (the theoretical area initially occupied by trees), rather than from the nominal size of the plot. Adjusted size of plots which are nominally 0.25-acre varies from 0.2296 to 0.2661 acre. Adjusted size of each half of the plot at 12-foot spacing is 0.2116 acre. Examination of stem maps revealed some errors in the previous determination of this adjusted plot size. Therefore, some per acre values in this report have been changed, relative to those reported previously. The greatest impact is on the 12-foot spacing, where the plot is 6.7 percent larger than previously believed; thus, all per acre values for this spacing are less than previously reported. GPO 988-388 The FOREST SERVICE of the U.S. Department of Agriculture is dedicated to the principle of multiple use management of the Nation's forest resources for sustained yields of wood, water, forage, wildlife, and recreation. Through forestry research, cooperation with the States and private forest owners, and management of the National Forests and National Grasslands, it strives as directed by Congress - to provide increasingly greater service to a growing Nation. The U.S. Department of Agriculture is an Equal Opportunity Employer. Applicants for all Department programs will be given equal consideration without regard to age, race, color, sex, religion, or national origin. |