REDUCED GROWTH OF STANDS AFTER CUTTING 439 



stand to obtain the growth of the stand (§ 277), is favored in studies 

 of cut-over lands, first, because such studies are usually made in many- 

 aged stands of mixed species, second, because the difficulty of sepa- 

 rating the age classes by area and age is even greater than on stands 

 before cutting; hence the application to these stands of yield tables 

 based on age is very difficult. 



The stimulation of growth on the trees left after logging is similar 

 in character to the beneficial effects of repeated thinnings on stands 

 under management. It undoubtedly increases the rate of yield per 

 acre over that realized if the natural processes of selection are not 

 interfered with. 



Two factors must be considered in analyzing this growth; first, 

 to what extent have the trees left on the area been liberated or given 

 increased growing space? — second, to what extent can they utilize or 

 monopolize the area released by cutting? The maximum of increased 

 growth would be found in a stand, either even- or many-aged, in which 

 the cutting was so evenly distributed as to affect all of the remaining 

 trees, and so light that the space released could all be absorbed by these 

 trees. 



When cutting is either too light or too poorly distributed to affect 

 all trees, the trees showing increased growth will be only a certain per 

 cent of the total number. This per cent of each diameter class which 

 will be released, as affected by the increased rate, will give the net 

 actual increase over the previous rate of growth. 



Table LXVI illustrates the data required in a study of increased 

 growth after cutting (p. 440). 



From a table of this character the average increase in growth may 

 be computed by weighting the rate of increase by the per cent of trees 

 affected; e.g., since 18 per cent of the trees are affected, an average 

 increase of 18 per cent of the difference between the two classes of trees, 

 those not affected and thus growing faster, can be added to the slower 

 or original rate to get the new average for the forest. 



338. Reduced Growth of Stands after Cutting. In heavier cuttings, 

 even on parts of the same cut-over area, openings may easily occur 

 from cutting even-aged or mature groups, which affect but few of the 

 remaining trees. These clear-cut spots will result in a net reduction 

 of current increment per acre for the forest, just as would the clear 

 cutting of a larger area. There is no possibility of increased growth 

 because there is no timber left on which to lay this growth. In even- 

 aged stands cut clear, the growth for the forest occurs on separate areas 

 of maturing timber, not on the areas cut over; the growth on cut-over 

 areas must result from reproduction of a new crop and come along in 

 time. Thus on heavily cut-over areas, in mixed age classes, a heavy 



