APPENDIX 



229 



12. Growth on mortality 



13. Potential increase rate 



14. Timber cut 



15. Unadjusted timber cut 



16. Cutting rate 



17. Adjustment factor 



18. Total volume of unadjusted = 



timber cut 



19. Net cubic-foot volume 



20. Net board-foot volume 



21. Ingrowth into 2-inch d.b.h.= 



class 



22. Planted ingrowth 



23. Survival rate 



24. Natural ingrowth 



25. Timber removed in stand = 



improvement or rehabili- 

 tation. 



= Potential increase rate 

 = Potential increase 



: Unadjusted timber cut 

 = Number of trees at 



beginning of the year 

 = Number of trees cut 



during the year 

 = Assumed total volume of 



timber cut 

 = Summation of number of 



trees (by d.b.h. class) 

 = Number of trees 



= Net cubic-foot volume 



= Planted ingrowth 



= Acres planted 



X Mortality 



-^Number of trees at the 

 beginning of the year 

 X Adjustment factor 

 X Cutting rate 



-H Number of trees at the 

 beginning of the year 



H-Total volume of unad- 

 justed timber cut 



X Net volume per tree 



XNet cubic-foot volume 



per tree 

 X Number of board feet 



per cubic foot 

 -|- Natural ingrowth 



X Number of trees planted X Survival rate 



per acre 

 -^Number of trees planted 



= Number of trees sur- 

 viving at 1.0 d.b.h. 



: Computed from equation #4, using extrapolated stand-structure quotient and radial 

 growth (See procedures under "sapling mortality") 



= Number of acres treated X Number of trees per acre 



removed 



Input modification: In addition to the above com- 

 putations, annual modifications were programed for 

 each input variable. This required computing "B" and 

 "C" modifiers. The "B" modifier reduced or increased 

 the input factors by the same amount each year, resulting 

 in a constant annual change. The "C" modifier reduced 

 or increased the AC factor the same amount each year 

 resulting in a varying rate of annual change. The use 

 of both "B" and "C" modifiers results in a second degree 

 polynomial of the form: 



(1) XN = a-f-bN + cN2 



where XN = input value after N annual cycles 

 a = initial value 

 b and c are regression coefficients 



(2) b = AC-f-^ 



(3) C-- 



RAC 



(4) AC = ACl- ^^^„"^^^ RAC 



(5) RAC = 



(6) ACl 



AC2-AC1 



0.5 (N1 + N2) 



X2-X1 

 Nl 



(7) AC2 = 



X3-X2 



N2 



where 



XI, X2, X3 are three points on a curve and Nl and 

 N2 are number of years between points. 



This program provided output data, by 2-inch diameter 

 classes, for inventory and net growth, timber cut, and 

 mortality, in terms of numbers of trees, square feet of 

 basal area, cubic feet, and board feet International Vi- 

 inch rule. Statistics by species and ownerships were 

 based upon proportions shown in the most recently com- 

 pleted forest survey. 



Sampling Errors: Surveys were designed to provide 

 sampling errors no greater than 3 percent per million 

 acres of commercial forest land, 5 percent per billion cubic 

 feet of growing stock in the East and 10 percent per billion 

 cubic feet in the West. However, because of cooperative 

 assistance contributed by forest industries. State forestry 

 divisions and other public agencies, sampling errors 

 actually achieved were often much lower than the maxi- 

 mum allowable as shown in the following table: 



