SEPARATION OF AREAS OF IMMATURE TIMBER 453 



able or are suppressed, are not considered, since the yield table for the 

 stand takes care of them. Only in many-aged stands must poles be 

 counted, or their area determined by per cent of the total, the former 

 method to be used if the yield table permits of direct comparison of 

 numbers, the later, if only the mature classes are shown in the table. 



349. Effect of Separation of Areas of Immature Timber on the 

 Density Factor for Mature Stands. The separation by area of the 

 immature age classes accomplishes more than the determination of 

 future 3'ield for these age classes. In the many-aged forest, the mature 

 timber is not segregated as it is in even-aged stands, but is intermingled 

 with areas of reproduction, saplings, and poles. In the attempt to 

 separate this mature timber into two or more age classes, either based 

 on diameter classes, or by age groups (§ 320 and § 323) it is necessary to 

 l)egin with a knowledge of the total area occupied by all the mature 

 age classes. If the area actually stocked with seedlings, saplings and 

 poles to the exclusion of mature timber is neglected, then the area appar- 

 ently required by the mature timber is greater than that actually 

 required, by just the amount of this error. In the even-aged forest 

 no such mistake is possible, and by analogy, its correction for the many- 

 aged forest must be undertaken. 



The effect of not separating the area of immature stands is to lower 

 the reduction per cent or apparent density factor for the mature age 

 class. E.g., a reduction per cent of 40 is found for mature timber when 

 it is assumed to occupy the entire area. Segregation of young timber 

 shows that one-half or 50 per cent of the area is occupied by these age 

 classes. The total area is 10,000 acres. The actual area occupied by 

 mature timber is now 5000 acres, which doubles its density, and gives 

 a density per cent of 80 instead of 40. 



At first glance it would appear that no difference is made in the cal- 

 culation of yield of these mature age classes by either assumption since 

 reduced area and increased density are reciprocal and refer to the same 

 actual stocking and volume and presumably the same future yield. 

 The benefit lies in the fact that the corrected density factor more nearly 

 indicates the rate of growth per year for the forest or on the average acre, 

 which is the information most needed in permanent management. 

 By separating the yield and area of the young tunber, it is possible 

 to predict the total actual yield of the forest over a long period, instead 

 of for the shorter period required to harvest timber now mature. Instead 

 of an extremely low per cent of density for mature timber and for the 

 forest, which would indicate the need of considerable reduction in yields 

 from the standard table (§316), the true conditions are revealed. 

 Finally, it gives the same data as to age classes for the manj'-aged 

 forests as are obtained by mapping for even-aged stands. 



