WOODLOT FORESTRY 



131 



grows so much faster; while the native 

 spruce and hemlock grow so slowly that 

 it is not best to favor them in the ord- 

 inary woodlot. 



Knowledge of the rate of growth is 

 especially valuable in choosing trees for 

 planting, as naturally slow growers 

 would not produce enough to pay inter- 

 est on the money invested. 



While moisture, heat, light, and soil 

 comprise the four great elements affect- 

 ing growth, and the character of the 

 species itself is very important, even in 

 the same district, these factors are sub- 

 ject to many variations. 



The steepness of the slope is an im- 

 portant factor, greatly modifying the 

 factors of light and moisture. 



The aspect (the direction in which 

 the slope faces, as east or west) is im- 

 portant, in modifying especially the 

 factors of heat and moisture, and to a 

 certain extent, of light. Thus, a south 

 slope, which becomes heated sooner in 

 the spring, is very much: more apt to 

 have growth start earlier,- and this 

 growth is more likely to be "nipped" by 

 a late frost, which is general over the 

 whole district, than would be the case 

 on a north slope. A south slope dries 

 out more than a north one. And as 

 between south and north slopes, so 

 between west and east ones; and on a 

 ridge running northwest to southeast, 

 for instance, the northeast slopes might 

 have very different conditions of growth 

 than the southwest ones. 



Wind is another factor, acting to a 

 small degree in modifying the forms of 

 trees, but much more important from 

 its modification of the factor of moist- 

 ure, and still more so in its mechanical 

 effects, in blowing down trees. 



In modifying the form of trees, this 

 is apparent mostly on exposed mountain 

 peaks, along the shore, etc., where a 

 dwarfed, bushy form is developed, best 

 to resist the winds. 



To prevent drying out of soils, a dense 

 border at the edge of the woods should 

 be maintained. 



Should the border of the woods be 

 open, it will be best to plant several 

 rows of such trees as Norway spruce to 

 act as a windbreak. 



The mechanical effect of wind that 



is the blowing over of trees in the forest 

 is its most important one. The re- 

 sistance of different species, as well as of 

 individuals grown under different con- 

 ditions, is a consideration of importance 

 in management. 



Species must be so selected and man- 

 aged that the danger of windfall is re- 

 duced to a minimum. Thus, a species 

 like the spruce with its shallow root 

 system, must be grown in closer stands, 

 and in more protected places than the 

 deep-rooted Scotch pine. Especially 

 in cuttings in dense stands, where re- 

 sistance to wind was provided by the 

 whole woods, trees must not be left to 

 stand too openly, as the danger from 

 being blown over by wind is too great. 

 This applies especially to shallow-rooted 

 species like spruce. With them differ- 

 ent forest practice must be adopted than 

 that used with wind firm species. 



So far we have discussed mainly the 

 natural factors of growth. But much 

 more important, generally, in their 

 damaging effects, are the factors pro- 

 duced by man himself or by conditions 

 which he causes. To a certain extent, 

 of course, these damaging agents are 

 entirely "natural" in their work, and 

 not the result of man's work. 



Most important is fire. Almost all 

 of our woods have been seriously affected 

 by fire. 



The effects of fire are many, and often 

 but little understood or noticed. Thus, 

 the ordinary, light ground fire, which is 

 not thought of as doing damage, burns 

 up the leaf -litter and vegetable mold, 

 which is so valuable in soil fertility. 

 From this alone, the loss is enough to 

 warrant great care in excluding fire. 

 Then, if there is arty seedling reproduc- 

 tion on the ground, this is generally 

 killed off, so that desirable new stock 

 cannot get established. 



If the fire is a bit more severe, enough 

 injury is done to the standing trees to 

 check growth, or at least weaken the 

 vitality of the trees. Generally a wound 

 is produced through which disease or 

 insects can enter and thus kill or serious- 

 ly affect the tree. Frequently the 

 young saplings and small poles are 

 killed outright, and thus only mature 

 trees past their prime are left standing. 



