MIXTURES OF SHADE BEARING SPECIES. 77 



4. jSIixturea of Shade hcariufj Species. 

 It is a general rale that the permanent preservation of a 

 mixture becomes more difficult in the same degree as the 

 species to be mixed differ in repect of light requirement, rate 

 of height growth, suitability of locality, and shape of trees. 

 Except as regards the latter, the ordinary European shade 

 bearing species approach each other in these respects ; hence 

 in their case the mixture is comparatively easy to maintain, 

 and they may generally be raised in woods of even age or 

 nearly so. 



(I. Mi.rfi/n's in High Forest, 

 (1.) Silver fir and spruce. — These two species resemble 

 each other as regards shape. They differ somewhat in their 

 demands on the locality, but over extensive areas both find 

 suitable conditions for a healthy development. They are 

 both shade bearing, but silver fir more so than spruce. The 

 most important point is, that spruce grows somewhat more 

 quickly during youth and is likely to injure the silver fir, but 

 when the latter has once pushed its head to the light the two 

 species hold their own against each other. In order to get 

 the silver fir safely over the first 20 or 30 years it must be 

 assisted against the spruce either by giving it a start of 5 — 10 

 years, or arranging the mixture according to groups, or 

 cutting away the spruce where it threatens the silver fir. 

 Where mixed woods of silver fir and spruce have to be re- 

 generated, it is usual to leave a larger number of silver fir 

 seed trees, and to keep the shelter wood rather dark. In this 

 way a larger proportion of young silver fir is secured ; then 

 more light is given to enable young spruce to come up, and 

 if this should not happen, the species is brought in by 

 planting. 



The advantages of the mixture are principally the 

 following : — 



{a.) Spruce protects silver fir against frost and drought 

 during early youth. 



