332 



FORESTS 



FORESTS 



stances it is prohibitive. For this reason, a young 

 stand should be allowed to wait until the material 

 to be removed has reached such a size that its sale 

 will pay for its removal ; and it should not be 

 thinned again until the material to be removed has 

 accumulated in sufficient quantity to pay for its 

 removal. If the wood more than pays for its 

 removal, so much the better ; but if it pays only 

 for its removal, the improvement is a net gain. 

 The farmer who knows the price of labor, the cost 

 of drawing to market, and the price to be secured, 

 can easily determine when a thinning may be 

 safely undertaken. 



In reply to the other objections, it may be 

 said that, when thinning is done properly, the 



Fig. 472. Dense stand ol young hard-woods in need of 

 moderate thinning. 



falling trees do little injury, they do not lodge 

 so that they can not be brought down with a twist 

 of a cant-hook, and the remaining trees do not 

 blow down. 



The principal object of thinning is to preserve 

 the balance between height-growth and diame- 

 ter-growth of the trees that are to form the 

 final stand. Increase in volume is determined by 

 height- and diameter-growth. If the trees stand 

 too close together, height-growth will be in excess, 

 followed by a reduction in vitality. If the trees 

 stand too far apart, diameter-growth will be in 

 excess, accompanied by large side limbs. In either 

 case the quantity and quality of the timber will 

 be affected. Therefore, by preserving the balance 

 between the two, an acre of land is made to 

 produce more and better lumber in a given period 

 of time. 



The extent to which a closed stand may be 

 opened depends on several conditions. The kind or 

 kinds of tree that compose the stand, the nature of 

 the soil, the character of the undergrowth, the 

 purpose for which the timber is grown, all play 

 a part in determining the degree of thinning. This 

 is one of the many matters in forestry that cannot 

 be reduced to a rule, but must be based on a study 

 of each woodlot. There are, however, several con- 

 siderations which indicate the extent to which a 

 woodlot may be thinned. The classes into which 

 trees in a closed stand gradually become separated, 

 in the course of their struggle for existence, are 



of assistance in selecting trees for removal. Four 

 classes are usually distinguished : (1) dominant, 

 (2) intermediate, (3) suppressed, and (4) dead. 

 Dominant trees are those that have their crowns 

 in the light ; they have kept ahead of the others 

 in height - growth. Intermediate trees are those- 

 that still have their crowns in the light, but are 

 somewhat backward, and are destined to become 

 suppressed in the near future. Suppressed trees 

 are those that stand slightly below the intermediate 

 class and will probably die within a few years. 

 Now, moderate thinning would involve the removal 

 of such of the intermediate trees as are interfering 

 with the best development of the dominant ones. 

 Care should be taken not to open up the stand to 

 such an extent that undesirable undergrowth will 

 result. In the case of shallow-rooted species, like 

 the spruce, the stand should not be opened up too 

 much or it will become liable to windfall. The 

 cover must be broken into enough, however, to 

 stimulate the growth of the remaining trees, or 

 very little good will have been accomplished by the 

 operation. In no case should the cover be broken 

 to such an extent that it will not close in two or 

 three years. 



Whether suppressed and dead trees should be 

 removed depends principally on whether they con- 

 tain enough wood to make their removal, along 

 with the remainder, worth while. Some stimulation 

 will result from the removal of certain of the 

 suppressed trees, but most of them are so far 

 behind the dominant trees that are to compose the 

 iinal stand that their presence or absence has little 

 effect, one way or the other, on the development 

 of the dominant ones. Yet it often pays to remove 

 some of the suppressed, and sometimes even a part 

 of the dead trees, while the more important thin- 

 ning is in progress, although, except in extraor- 

 dinary cases, it would not pay to go into a stand for 

 suppressed and dead trees alone. On the general 

 principle of cleaning a stand of all useless material 

 that might add to the dissemination of disease or 

 increase the danger from fire, it is sometimes ex- 

 pedient to remove dead and suppressed trees, when 

 it can be done without extra cost, while thinning 

 is being done. On the other hand, it is sometfmes 

 desirable to retain the suppressed trees, or a part 

 of them, in order to keep the ground as well shaded 

 as possible. 



Certain species in a mixed stand are more desir- 

 able than others. If it comes to a choice between 

 two trees of different species, other things being 

 equal, the more desirable kind will be left. For 

 example, a white ash and a yellow birch tree are 

 standing side by side, and the conditions demand 

 that one should be removed ; the birch would be 

 removed and the ash should be allowed to grow, 

 for white ash logs sell for over twice as much as 

 yellow birch. 



A defect in an individual of a desirable kind 

 may render it less valuable than a tree of inferior 

 kind. For example, a decayed spot in the ash 

 mentioned above may have made its removal pref- 

 erable to that of the yellow birch. 



The shape of the crown and its position relative 



