CONIFEROUS FOREST TREES IN GREAT BRITAIN. 7 I 



forward when the mixing is by groups. It is the method which 

 has been generally followed in recent years, and it should 

 be continued until experiments demonstrate a better method. 



The method of underplanting with shade-bearers will now be 

 considered. It has been tried on a small scale in several places, 

 notably at Novar in Ross-shire. Underplanting can be used 

 to meet two different situations — first, where a larch crop has 

 become open at an early age owing to deaths from larch canker, 

 and secondly, when the crop opens naturally at a later period. 

 In the first case, it would appear that a shade-bearing conifer 

 should be used, as not only should an effort be made to protect 

 the soil, but also to replace, so far as possible, the depleted 

 larch increment. In the second case a hardwood, such as 

 beech, would appear to be most useful. For under such condi- 

 tions the shade would be greater than in the first case, so that 

 no conifer would grow fast enough to reach a measurable size 

 before the end of a moderate rotation. Thus, as the only use of 

 the underplanted tree would be as a soil improver, the best species 

 for that purpose should be chosen, viz. beech. The choice of 

 the most suitable conifer for the first set of conditions is a 

 matter of importance. The principal requirement is fairly rapid 

 growth under considerable shade. For this reason Douglas fir 

 does not generally give very satisfactory results unless the wood 

 has become very open. The silver firs naturally suggest them- 

 selves, and of the silvers Abies grandis is probably safest, owing 

 to its apparent immunity from the destructive silver fir Chermes 

 pest. The rate of growth of silver firs, however, is slow in early 

 life. Tsuga Albertiana, Thuya species, and Cupressus species 

 all require further trials. Experiments have already been made 

 to determine the best species for this purpose, but they require 

 to be extended to include a wider range of environmental 

 conditions. 



The principal objection to the method is the difficulty of 

 tending the resulting plantation. If one favours the larch crop, 

 many of the underplanted species are sacrificed before they are 

 a marketable size, while if the lower crop is favoured by the 

 gradual removal of the larch, the final crop is rather patchy and 

 irregular. 



A third method is to grow the larch pure and follow it with 

 a soil-improving species on a short rotation. For instance, a 

 60-70-year larch rotation could be followed by a 30-40 Scots 



