PURE WOODS OR MIXED WOODS ? 85 



The arrangement of more permanent mixtures requires still 

 more care, since it depends on the relative height growth, the 

 light requirement, and shape of the species in mixtures, Hence, 

 it is of the utmost importance to restrict mixtures to as few 

 species as possible. Pure woods are easier to manage than 

 mixed woods ; mixtures of two easier than mixtures of three 

 or more. It is far better to mix two species on half the area, 

 and two others on the second half, than to mix four species 

 over the whole area. 



In summing up, we arrive at the following simple rules : 



(1.) Only species which are capable of preserving the yield- 

 capacity of the locality may be raised in pure woods. 



(2.) In the case of mixed woods, at any rate one of the 

 species in mixture must be soil-improving, and it should be 

 more numerous than the others. 



(3.) As a rule, not more than two, and certainly not more 

 than three, species should be mixed on the same area, unless 

 each species is placed into separate groups, representing a series 

 of small pure woods. 



(4.) Shade-bearing species may be mixed with each other, 

 provided their rate of height growth is the same, or the slower- 

 growing can be effectually protected against the other, either 

 by giving it a start, or cutting away the threatening individuals 

 of the faster growing species. 



(5.) Shade-bearing and light-demanding species may be 

 mixed, if the latter are faster growing, or given a start. 



(6.) Light- demanding species should not be mixed with 

 each other, except under exceptional conditions, such as the 

 following : 



(a) In very fertile localities. 



(b) In very inferior localities where nothing else will grow, 



(c) If the mixture is a temporary one, as in the case of nurses 



grown to protect a tender species during early youth ; 

 or if the wood is treated under a very short rotation, as, 

 for instance, where only pit timber is grown. 

 (7.) Whether the mixture should be arranged by single trees, 



