FORMATION OF MIXED WOODS. 75 



Llylit requirement. — The mixture must be so arranged that 

 the hght demandmg species are not likely to be shaded by 

 other trees ; in fact, they must have their heads free and ex- 

 posed to the light. Some species, such as silver fir and beech, 

 like, and even require, some shelter during early youth. 

 Mixtures should be so arranged as to provide such shelter, 

 whenever it is required. After the first few years no species 

 actually requires shade, and then species are either shade 

 bearing or light demanding. In most cases the former will 

 bear the shade of the latter, but the reverse is not the 

 case. 



Heu/ht ijrowth. — All species which demand space and light 

 when mixed with species of an opposite nature, must be of 

 quicker height growth than the latter, or be given a start. 

 Hence the relative height growth of the species must be fully 

 considered in deciding on the nature of the mixture. In 

 many cases it is necessary to produce woods of uneven age, 

 in order to prevent the light demanding species from being 

 overgrown and suppressed by the other species. 



Assuming then, that the locality suits in a general way all 

 the species to be mixed, the following rules govern the selec- 

 tion and formation of mixtures : — 



First Rule. — The ruling (more numerous) species must be 

 soil improving. 



It has been stated above under what conditions exceptions 

 from this rule are admissible. 



Second Rule. — Shade bearing species may be mixed with 

 each other, provided their height growth is of the same 

 rapidity, or the slower growing species can be etfectually 

 protected against the faster growing. 



Third Rule. — Shade bearing species may be mixed with 

 light demanding species, if the latter are either faster 

 growing, or are given a start. 



To prevent the shade bearing species being kept back in 

 its growth it should be more numerous than the light 

 demanding species. 



