CHAP. V.] 



Soil and Situation 



107 



For trees forming a decided tap-root like the Oak, Scots 

 Pine, and Larch depth of soil is of very great importance ; 

 for, unless the root-systems can develop normally, the growth 

 in height of the trees becomes prejudicially affected. But trees 

 with only moderately deep root-systems, like Beech, Horn- 

 beam , Silver and Douglas Firs, or even rather shallow-rooting 

 kinds like Birch, Aspen, and Spruce, also thrive better on deep 

 than on shallow soils, as these latter generally contain more 

 equable supplies of soil-moisture, and larger stores of food- 

 material in an easily available, soluble form. Deep soils are 

 much less apt to dry up or to become too moist than shallow 

 soils ; and the disadvantages of the latter are intensified when 

 the subsoil happens to consist of horizontal layers of stiff clay 

 or other impermeable strata, or of ferruginous deposits like 

 moorpan or limonite. The following is the classification of 

 soils as to depth adopted at the sylvicultural experimental 

 stations throughout Germany : 



But in Britain, as a matter of fact, woodland soils will 

 seldom be found of great depth : for, when deep, they can 

 generally be used to better economic and financial advantage 

 as arable or pasture land. 



