216 THE I'RIKCTI'LES OF HANUUNG WOODLANDS 



reasons. Wherever there is danger from windfall, a 

 stand must be opened gradually by moderate and fre- 

 quent thinnings. In the same way, stands of trees with 

 thin bark must be opened gradually to prevent sun- 

 scald, which frequently occurs, for instance, with second- 

 growth white pine. 



It is often necessar)' to make openings in the canopy 

 which will be more or less permanent. This occurs 

 when groups of damaged trees have to be removed. 



Accretion Cuttings 



It is a well-known fact that when stands are heavily 

 thinned the trees usually show a marked increase in 

 growth. This is due to the greater amount of light, and 

 the stimulation this gives to the activity of assimilation. 

 The increased growth ma\' be called light growth. It 

 takes place after thinnings when, b\' crowding, the cro>Ans 

 have been prevented from receiving as much light as 

 they could utilize; when the trees are vigorous enough to 

 respond to the new conditions; and when there is enough 

 moisture and nourishment in the soil to meet the require- 

 ments of the increasingly active crowns. 



The endeavor of modern forestrv is to obtain the 

 greatest possible light growth, particularlv during the 

 last half of a stand's rotation. Practically all foresters are 

 agreed that during the first part of the rotation the forest 

 must be kept dense to produce trees of good form. The 

 principal difference in methods concerns the handling 

 of the stand to secure the maximimi light growth. 



