190 A MANUAL OF FORESTRY. 



with, the desired result. The effects of the locality 

 upon forest vegetation, and vice versa, have been dealt 

 with in Chapter I. of Volume I. of this Manual, while 

 the protection of the soil and growing wood against 

 injurious influences will be dealt with in a subsequent 

 volume on Forest Protection. In this place the im- 

 portant points will only be shortly indicated, with 

 special reference to the sylvicultural aspect of the 

 subject. 



In order that a crop may be fully productive, it is 

 necessary to establish and then to preserve those physical 

 and chemical conditions of the soil on which a healthy 

 and vigorous growth depends. The means adopted in 

 agriculture for this purpose are working the soil and 

 manuring. Both are expensive, and in Sylviculture they 

 are only feasible in cases where the increased returns 

 at least cover the outlay ; they are therefore either out 

 of the question or can only be employed to a very 

 limited extent, and the forester must endeavour to accom- 

 plish what is needful by other means. Fortunately 

 timber trees are far less exacting than field crops, so 

 that the more modest means at the disposal of the forester 

 suffice for their healthy development. 



It has been shown on page 137 of Volume I., that 

 the productive power of the soil in Sylviculture depends 

 on : 



(1.) A sufficient depth; 

 (2.) A suitable degree of porosity ; 

 (3.) ,, moisture; 



(4.) ,, chemical composition. 



For sylvicultural purposes these conditions can be 



