904 



A NATIONAL PLAN" FOR AMERICAN FORESTRY 



ADJUSTING GROWING STOCK TO PRODUCE MAXIMUM RETURNS 



It has already been pointed out that on forest properties expected 

 to pay their way under private forest management the growing stock 

 usually represents 80 to 95 percent of the total investment. Two 

 factors dictate that a growing stock of varying ages be carried at all 

 times : first, valuable merchantable material is produced only by many 

 years' growth of a tree or stand ; second, annual income can be obtained 

 only by maintaining a succession of size classes, so that as the larger 

 trees are cut others grow up to take their place. 



CUTTING AND MANAGEMENT SYSTEMS 



The many silvicultural systems recognized (4) form two major 

 systems of handling cuttings in saw-timber forests as regards treat- 

 ment of trees of different ages or sizes. The clear-cutting system 

 (fig. 1) removes the complete stand at once over considerable areas, 



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AGE CLASSES 



FIGURE 1. Forest with series of even-aged stands. 



with the result that if another stand follows it grows up even aged. 

 The chief defects of this system are that natural regeneration often 

 does not follow and that a large portion of the trees cut are removed at 

 a loss when they might have been left to add valuable growth and 

 reach maturity at an early date. The American forest regions in 

 which this system has generally been followed have the most seriously 

 depleted forests. 



The selection or partial-cutting system (fig. 2) removes trees of 

 merchantable size either individually or in groups with the minimum 

 interference to the growing trees left. Young stock develops on the 

 same ground occupied by the larger trees or in small openings, with 

 little or no assistance or cost. The proper arrangement of cuttings 

 among the larger trees aims to maintain on every division of the forest 

 a growing stock of trees from 6 to 40 inches or more in diameter which 

 are capable of earning currently through their continued growth the 

 income necessary to pay all the operating costs and a net income be- 

 sides. This income is not taken annually on every acre; the cut is 

 rotated over the area once every 5 to 20 years. At each return to a 

 given area 5 to 20 years' growth is harvested. The range of diameter 

 classes in the stand varies with the species. 



In considering the present condition of the growing stock in various 

 forest types, its progressive modification in the course of cuttings to 

 obtain current income, and the reservation of trees of proper sizes 

 and characteristics to provide the best possible continued growth and 



