CONIFEROUS FOREST TREES IN GREAT BRITAIN. 69 



saving not only in plants but also in labour. These observa- 

 tions apply to all species, but they have much greater force in 

 the case of larch, which is a light-demanding species liable to 

 disease and with a rapid height-growth in early life, than in the 

 case of a species such as spruce, which is a shade-bearer and 

 grows relatively slowly in early life. In the author's opinion, 

 the planting distance for larch should not be less than 5 feet, 

 and probably 6 feet will give the best results under most con- 

 ditions. The same principle should be followed in the tending 

 of larch plantations. They should be thinned early and then 

 every 5-10 years. The thinnings should be moderate to heavy, 

 depending on individual requirements. Only in this way can 

 this species be kept healthy. This method of treatment, how- 

 ever, means that the soil is more or less exposed, hence it 

 deteriorates. This leads to a consideration of the methods 

 that may be employed to preserve and increase the fertility 

 of forest soils carrying larch crops. 



Of the different methods that may be used, the following 

 will be briefly considered : — 



1. Mixture with a shade-bearing species. 



2. Underplanting with a shade-bearer. 



3. The rotating of pure larch crops with shade-bearing, 



humus-forming crops. 



Woods may be mixed either in blocks or by individual trees. 

 Mixture by individual trees will be considered first. Many of 

 the larch woods in Scotland are, or have been at some time in 

 their history, mixed woods. The species mixed were larch and 

 Scots pine, and the proportion generally two-thirds Scots pine 

 to one-third of larch. There are large areas available to study 

 the result of this mixture. Unless the conditions are very 

 unfavourable to the larch, the rate of height-growth of this 

 species exceeds that of the Scots pine right from the formation 

 of the plantation. The general result is that the Scots pine are 

 suppressed, and die out either before or during the time they 

 are required as the shade-bearing, humus-forming species. 

 Moreover, in many cases the resulting crop of larch is incom- 

 plete, with a corresponding loss of increment. There are two 

 very strong reasons against a Scots pine-larch mixture. First, 

 the relative rates of height-growth of the two species differ 

 considerably, and second, as has already been stated, the 



