110 FORESTRY WORK 



and air to reach the soil, drying up leaves, which are 

 thus prevented from decaying and so becoming available 

 as a source of plant food. 



Suppression of Side-Branches. 



To produce the highest quality of timber, the side- 

 branches of the trees must be suppressed or killed off 

 before they produce large knots in the bole. 



The side-branches on shade-bearing trees are very 

 persistent, and can only be suppressed by closely adjoining 

 trees of equal density. Some light-foliaged trees grow 

 the side-branches too strongly, spoiling the quality of 

 timber, and these can be suppressed only by mixing with 

 trees of greater density. 



Eapidity oj Growth. 



Some trees naturally grow more rapidly than others, 

 and consequently in a mixture by single trees those that 

 grow more slowly are suppressed by the rapid growers. 

 The same result follows in similar mixtures made on a 

 soil suited to one species only those that the soil does 

 not suit will be suppressed. 



The Advantages of Pure Plantations. 



They are more easily planted and tended, and the 

 trees all reach maturity at the same time. 



With heavy-foliaged, shade-bearing trees, the side- 

 branches are suppressed more readily than if mixed with 

 light-foliaged trees. 



