ioo BRITISH FOREST TREES 



genial, it is the most important associate of the spruce ; 

 and though during the earlier years of growth it must be 

 granted some protection against the more rapidly developing 

 spruce, it requires no special tending throughout the later 

 stages of growth. In many respects it adapts itself better for 

 admixture with the spruce than with any other ruling 

 species of forest tree. In tree-form and natural development 

 they have many close resemblances, but as silver fir is 

 deeper-rooted than spruce, the two species, admixed, can 

 develop unhindered a much larger aggregate of roots than if 

 either species were grown in pure crop ; and as this maximum 

 of root-system has practically the opportunity of drawing the 

 requisite supplies of nutriment from two different layers 

 of soil, it follows naturally that the number of stems and the 

 total production of timber per acre will under ordinary 

 circumstances be considerably greater than can be shown by 

 pure forests of either species. By interlacing of the two 

 root-systems also, no inconsiderable support is given to the 

 shallow-rooting spruce against windfall. 



The main condition for the formation of mixed forests of 

 spruce and silver fir is a good deep soil without excess of 

 soil-moisture, as unless that essential condition be satisfied 

 the latter is unable to maintain itself against the former. 

 Even although developing slowly at first as compared with 

 Scots pine, spruce has a more rapid early growth than the 

 silver fir, and the advantage thus won it maintains throughout 

 the pole-forest and into the tree-forest stage of development. 

 Although the silver fir can thrive in the side-shade cast by the 

 spruce, measures must be taken to prevent the latter shooting 

 so far ahead as to form canopy above the silver fir in the 

 thicket stage of growth, otherwise the latter dies off. Where 

 the two species are planted out alternately in equal numbers, 

 the silver fir soon gets defeated in the life-struggle, unless 

 the soil is of better than average quality. Even when the 



