COMPOSITION OF FORESTS GROWN EXCLUSIVELY FOR THE MARKET. 117 



much stronger plea for pure forests than that discussed in the pre- 

 ceding paragraph, but here also, as in that case, the possibility of 

 creating or maintaining a pure forest, without any risk of some 

 strong countervailing disadvantage or disadvantages, must be 

 previously established. 



SECTION IT. 

 Composition of forests grown exclusively for the market. 



In raising and cultivating such forests, the main object to secure 

 is to obtain the maximum and most useful production of which 

 the soil and climate combined are capable. 



To obtain the maximum production alone the following condi- 

 tions must co-exist : 



( i) The forests must be composed of the most suitable species for 

 tJie given soil and climate. Both these elements usually vary from 

 place to place and often even from point to point, and the species 

 must of course vary accordingly, since there is no single one that 

 will grow equally well under constantly changing conditions of 

 soil and climate. Hence unfailing advantage in a mixture of 

 species, save perhaps in the very exceptional case of the more or 

 less perfect uniformity of both these factors of vegetation. 



(\\) The forests should consist of the greatest number of stems 

 possible at any given stage of growth compatible with the healthy 

 and projitable expansion of the trees. This is secured by constantly 

 maintaining as complete a leaf-canopy as possible a result, as 

 shown under Advantages I, II and III ot a mixture of species 

 (pp. 109 110), best attained by means of a mixture of species pos- 

 sessing different habits, different requirements as to soil, situation, 

 and aspect, and a different ramification and spread of roots, besides 

 making different rates of growth, and reaching different statures. 



(iii) The trees should attain the greatest length of bole possible 

 under the given conditions of soil and climate. This end also, as ex- 

 plained under advantage II and III (pp. 109 110), is best se- 

 cured by a mixture of species, thanks to which the trees attain va- 

 rious heights, their crowns press up one against another, and the 

 depth of the leaf-canopy is always maintained at its maximum, the 

 result being forcing in height and rapid elongation of the boles up 

 to the maximum limit possible for each species. 



(iv) We must have continued improvement of the soil until its 

 maximum fertility is reached, and constant maintenance of that 

 maximum thereafter. To secure this end we must have 



