DIVISION OF FORESTRY. 



221 



■was obtained by counting the trees of a naturally-grown, dense Nor- 

 way spruce forest at different ages. 



20 years 

 40 years 

 60 years 

 80 years 

 100 years 

 130 years 



Number. 

 9,377 

 1,265 

 604 

 393 

 2.S5 

 241 



standing 



room per 



tree. 



Square ft. 

 4.64 

 34.43 

 72.11 

 110.70 

 156.00 

 180.75 



Such a table is most instructive in many wa^^s. If, for instance, as 

 appears, only 733 trees per acre can reach, a satisfactory development 

 in 40 years, why plant more of a costly, valuable kind? Why not 

 limit ourselves to that number at first, and for the purpose of shading 

 the ground and stimulating growth fill up the space between them 

 with a cheaper material? 



It shows that the struggle for dominance is severest in the period 

 from the twentieth to the fortieth year, gradually decreasing with 

 advancing age. From this we may infer that interlucations are most 

 effective in the earlier period. It shows us that those trees which are 

 now dominant, seemingly in full vigor, may yet be overshaded and 

 at last subdued by their neighbors. Thus we may group the trees of 

 the naturally grown forest into the following classes : 



1. The fore-grown or dominant; which might be subdivided into 

 (a) predominant, (b) codominant, (c) followers. 



2. The overshaded; subdivided into (d) overwhelmed and (e) sub- 

 dued. 



By interlucations we imitate, assist, anticipate nature in this process 

 of elimination, and according to the degree of our thinning we speak 

 of a dark interlucation, which removes only the subdued, dead, and 

 dying stems^ a moderate one, which takes all the overgrown, and a 

 severe one, which attacks also the lowest grades of the fore-grown, 

 and even interrupts somewhat the upper crown cover. The degree of 

 interlucation to be practiced depends greatly on the soil and the ex- 

 posure; a dark interlucation is in most cases sufficient. 



The necessity of a stronger interlucation presents itself in a growth 

 with an unusually large number of stems of uniform caliber, where 

 sometimes the struggle for supremacy is unduly prolonged and the 

 lessening of overstock is needed to secure the development of larger 

 dimensions. Predominant stems ought to be taken only exception- 

 ally, when a more valuable kind, which we want to favor — as, for in- 

 stance, white oak — is in danger of being overwhelmed by a less val- 

 uable overgrowing neighbor ; or when, on account of some peculiari- 

 ties of an accidentally foregrown species of tree, detrimental conse- 

 quences must be anticipated, as, for instance, when the birch (which 

 only too easily finds entrance into our plantations), with its whipping 

 branches, may in^"ure and strip the young buds of the pine or fir. 



A deep, rich soil, with abundant moisture, on northern and north- 

 western exposures, will endure a strong interlucation with least in- 

 jury, because the vigorous growth due to its favorable conditions will 

 soonest close any gaps. On the other hand, it will almost always be 

 well to leave even subdued stems on thin and dry soils and those ex- 

 posed places where by their removal entrance would be given to dry- 

 ing winds and. sun. 



