UNEVEN AGED WOODS. 259 



they can be given a start up to 30 or 40 years. After these have 

 been regenerated, tlie groups consisting of the threatening 

 species are taken in hand. Taking, for instance, a mixture of 

 light demanding and shade bearing species, such as oak, larch, 

 or Scotch pine, ^Yith beech, silver fir or spruce, operations 

 commence with the groups of the former, and are brought to 

 a close by a regeneration of the latter. 



Again, in a mixture of shade bearers only, such as beech, 

 silver fir and spruce, the last mentioned is likely to outgrow 

 the beech and also the silver fir ; hence a sufficient n amber of 

 groups of beech and silver fir are first established, and then 

 the groups of the spruce. 



In the case of selection forests the differences in age are still 

 greater, and much can be done on the lines indicated above, 

 to protect the threatened against the threatening species. 



b. Nif/h Forest irith Standards. 



If such woods are mixed, the threatened species are selected 

 for standards, if otherwise suitable for the purpose ; it is 

 essential that the rotation should not be very high, otherwise 

 the future standards may suffer l)efore the end of the rotation 

 has been reached. 



c. Two-storied High Forest. 



It has been explained in Part I., page 103, that when a high 

 forest has run through part of the fixed rotation, a portion 

 of the trees are removed, and a new crop is introduced, which 

 grows up between the trees remaining of the first crop, the 

 two being allowed to run through an additional whole rotation. 

 The difference between the two crops ranges, as a rule, from 

 20 to 60 years. Here then is an excellent opportunity of pro- 

 tecting a threatened against a threatening species, the first 

 crop consisting of the former, and the second of the latter. 

 In Europe the system is much adopted for the production of 

 large- sized oak, larch and Scotch pine, also ash, maple and 

 others, which at a certain age are underplanted with beech, 



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