438 CURRENT OR PERIODIC GROWTH OF STANDS 



since the suppression of diameter growth is to be avoided, and this begins 

 considerably in advance of the death of the tree and may affect the 

 entire stand if too crowded. 



By this method, neither a full volume analysis of current growth 

 of trees is needed on the one hand, nor a yield table based on area and 

 age on the other. Nor is it necessaiy to compute the average tree of 

 the stand, and by predicting the growth of this tree for the next decade, 

 seek to determine that of the stand (§ 275) since all the trees in the stand 

 are given their proper weight in predicting growth. Only for very 

 regular stands can average trees be used safely, and for such stands 

 yield tables are better. 



337. Increased Growth of Stands after Cutting. The method of 

 predicting diameter and volume growth of trees after release by cutting 

 is shown in § 280. The problem of predicting growth of stands left 

 on cut-over lands is one of properly combining the growth data for the 

 different classes of trees left on the area. 



That diameter growth of individual trees should increase when 

 their crowns and roots are given increased growing space is a natural 

 law of growth of stands. The question is, " What is the total net 

 current growth per acre on such lands? " 



The first result of cutting should be to tremendously increase the 

 growth per cent on the remaining stand, or change its status, by removing 

 large, old and slow-growing trees with a low growth per cent, and leaving 

 small, young and more vigorous trees with a larger growth per cent. 

 This change would occur even if no increased growth followed the cutting. 



The total growth per acre laid on after cutting is the sum of the 

 current increments on the residual trees. In spite of change in growth 

 per cent or status, and of possible increased growth on the trees left, 

 the total net volume increase may be less than on the original stand. 

 If the number of trees is greatly reduced this is usually the case. But 

 if the stand cut over is many-aged, and only the decadent and sup- 

 pressed trees are taken, the combination of a large number of trees 

 left on the area, an increased rate of growth on these trees, and especially 

 the prevention, by cutting, of a loss of volume by death of trees which 

 would otherwise have to be deducted from current growth, may result 

 in a larger actual net increase per acre from the cut-over stand than 

 before it was cut, as well as a greater growth per cent. 



This expansion of diameter and volume growth of the residual 

 stand after cutting, is, for even-aged stands, a response to increased 

 light, soil, moisture and space in which to expand. In many-aged 

 stands it may mean, as well, an expansion of the total area of the age 

 class (§253). 



The method of determining the growth of individual trees in the 



