72 ELEMENTS OF SYLVICULTUEE. 



to ensure the maintenance of the oak and constantly 

 to improve its growth. This role belongs to clean- 

 ings and thinnings. 



Until the crop has reached the low pole stage, 

 cleanings alone have to be made. Their urgency is 

 in proportion to the richness of the soil and the mild- 

 ness of the climate. Unless the hornbeam occurs 

 as stool-shoots, it must not be removed in the clean- 

 ings, because its growth is slower than that of 

 the oak ; but we may remove beech, trees of less 

 importance, soft-wooded trees and brushwood. For 

 instance, on sandy soils it will be the beech that must 

 be specially guarded against ; on sandy clays the 

 beech, soft-woods and other inferior kinds ; on lime- 

 stones and calcareous clays, the beech and brush- 

 wood. The chief points to attend to are never to 

 create gaps in the leaf-canopy, to top off in prefer- 

 ence to cutting back, to make no wholesale extrac- 

 tion of any species that may be got rid of by degrees 

 and with more profit in the thinnings later on, and 

 to set free only as many oaks as are necessary (two 

 hundred to two hundred and fifty, well distributed, 

 per acre). These cleanings are to be repeated as the 

 circumstances require, without striving to make their 

 yield more remunerative by postponing them to a 

 later period. 



Thinnings acquire a capital importance whenever 

 the beech is associated with the oak, because they 

 are then merely a continuation of cleanings at every 

 stage. In making them, the end to be attained 

 should be clearly and steadily kept in view, and that 

 is to set free the crown of the oak, without isolating 

 its bole. 



