20 A MANUAL OF FORESTRY. 



the surface on the outside for 6 to 12 inches and cover 

 it lightly with soil. 



Against ordinary cattle a height of 4 feet is sufficient, 

 but against deer the fence should be 6 and even 7 feet 

 high. 



SECTION III. EECLAMATION OF THE SOIL. 



Soil may be called fertile for sylvicultural purposes, 

 if it possess sufficient depth, a suitable degree of poro- 

 sity and moisture, and a suitable chemical composi- 

 tion.* Forest soil, if undisturbed, will in most cases 

 maintain, or even acquire, those physical conditions 

 which render regular artificial tillage unnecessary, f 

 Immediately before and during the formation of a wood, 

 however, certain things may have to be done to render 

 the soil fit for the growth of trees, and to enable the 

 latter to make a start. These measures may be divided 

 into the following two groups : 



(a.) Eeclamation of soil unfit for the growth of trees, 



and 

 (.) Tillage of the soil concurrent with the formation 



of a wood. 



The latter will be dealt with in connection with the 

 various methods of starting a wood. Group (a) includes 

 the following measures : 



1. Treatment of an impermeable substratum. 



2. Treatment of swampy ground generally. 



3. Irrigation of arid ground. 



4. Treatment of excessive layers of vegetable matter. 



* See page 137 of Volume I. 



t See pages 20 and 145 of Volume I. 



