ADVANTAGEH OF MIXED WOODS. 71 



Section II. — Mixed Woods. 



A mixed wood may be so arranged that every tree of one 

 species alternates with a tree of another species, in which 

 case the mixture is called one hy single trees. Or a group of 

 trees of one species may alternate with a group of trees of 

 another species, called a mixture hy groups ; in the latter case 

 the groups must not be of such extent, that each acquires the 

 character of a pure wood.- Mixtures may also be arranged in 

 alternate lines or strips. 



Mixed woods may be : — 



(a.) Permanent or temporary. 

 (b.) Even aged or uneven aged. 



Temporary mixtures are ordinarily called for in the following 

 cases : — 



(1.) When the intention is to obtain an early return, by the 

 removal of one of the species, which should in that case be of 

 rapid growth. 



(2.) When a tender species has to be protected (nursed) 

 during early youth against frost or drought, as beech and 

 silver fir, and to a less degree oak. In this case a hardy and 

 fast growing species, such as Scotch pine, larch, birch, is 

 raised either simultaneously or beforehand, and removed 

 when the tender species requires no further protection. Near 

 the sea coast, it is generally necessary to grow first very 

 hardy trees, so as to establish sufficient shelter ; more 

 valuable trees may afterwards be introduced between the 

 nurses. 



(3.) When both the above objects are combined. 



Permanent mixtures are established, because they are con- 

 sidered to have advantages over pure woods. 



1. Advantages of Mixed Woods, 

 (a.) Mixed woods admit of a more complete utilisation of the 

 factors of the locality, and consequently they produce a larger 

 quantity of wood, if the mixture is suitably arranged. Each 



