THE THEORY AND PRACTICE OF WORKING PLANS 89 



ment if the growing stock is too small, or cutting more if it is 

 too large. 



(5) The period of equalization (x) of excess or deficit, i.e., 

 the time during which an abnormal stand is to approach nor- 

 mality, can be determined only with regard to local exigencies, 

 it must be developed out of a general plan of management 

 which is in consonance with the wishes of the owner. If v<nv 

 then X must equal at least a period of years sufficient so that the 

 sum of the actual increments during that period equals the 

 diiTerence between v and nv; where this is exactly the case 

 then y (the annual cut) equals o. 



On these premises Heyer develops the formula: 



v-i-ix — nv 



y= ; 



X 



i is the actual mean annual increment, and hence really varies 

 from year to year. Hence as i improves, the approach toward 

 normality is accelerated to less than x years, as it grows smaller 

 the approach toward normality is retarded to more than x 

 years. This variation of i Heyer meets by calculating i not 

 solely according to its present condition, but by conceiving 

 of the expression ix as the increment during the period of x 

 years, with regard to all the probable changes in increment 

 during the x years. This is facilitated by the drawing up of a 

 plan of cutting (distribution of cut) as outlined further on in 

 the present chapter. 



nv is found by the formula — in which Heyer takes i as the 



2 



normal mean annual increment, but at the same time raises 



the question whether taking i as the actual mean annual would 



not be equally correct.* (It has now come to be universally 



considered as the correct method.) 



(b) Example. — ^An uneven-aged forest of Western yellow 



pine contains 3,500,000 feet board measure of timber 12 inches 



* Judeich, " Forsteinrichtung " in Lorey's " Handbuch der Forstwissen- 

 schaft," 2d edition, Vol. Ill, p. 425, foot-note. 



