110 OUR FORESTS AND WOODLANDS 
cation is essentially necessary in growing crops 
of oaks. Asa tree making strong demands for 
light, however, what would be a moderate thinning 
for beech would prove insufficient for oak ; hence, 
in conducting thinning operations in oakwoods, 
the requirements as to growing-space for the 
next four or five years should be anticipated and 
provided for. 
In thus dealing with crops or groups of oak, 
the somewhat anticipatory thinnings should re- 
move all stems that are not necessary for the 
maintenance of the /eaf-canopy or crown of 
foliage of the wood; because crowding of the 
individual poles, indefiniteness with regard to 
what will form the predominating stems through- 
out the crop, and a long struggle for supremacy 
over surrounding competitors for the available 
supplies of light, are even less desirable in oak-~ 
woods than in other hardwood crops. When the 
trees are older, even the formation of a small 
blank here and there is preferable to inter- 
ference with the crown of foliage of the best 
trees, as such blanks often soon close up again. 
But when thinning is neglected, or is delayed too 
long, or is carried out insufficiently, the further 
