148 Studies in Forestry [CHAP. vu. 



useful as a nurse in localities exposed to frosts, an admixture 

 of Birch is not much favoured. The reason is more especially 

 owing to its strong reproductive capacity from the stool ; for it 

 is extremely difficult to get rid of the latter tree when it is no 

 longer desired as part of the crop. 



Aspen and Willow are also prejudicial to the development 

 of the Spruce, but not to the same extent as the Birch. 



Spruce with Scots Pine. During the earliest period of 

 development the quicker-growing Pine affords the Spruce 

 beneficial protection against frost and heat; but the Pine 

 cannot exceed one-fifth to one-seventh of the crop without 

 threatening to interfere for a long time with the normal growth 

 of the Spruce. Later on the Pine, owing to its tendency towards 

 a spreading crown, does more or less damage by rubbing and 

 scouring the shoots of the Spruce. On some situations the 

 Pine lags behind the Spruce in growth between the thirty-fifth 

 to fiftieth year ; but on good soil it regains the lost advantage, 

 and continues till maturity among the dominating or pre- 

 dominating classes. In other localities observations have 

 shown that on somewhat dry sandy soils the Pine is of quicker 

 growth throughout its whole period of development ; whilst 

 on fresh soils the Spruce shoots continuously ahead when 

 once it has caught the other up. A permanent mixture of 

 these trees is as a rule only recommendable on medium 

 classes of soil ; but by this means the Pine can be made to 

 hold out longer periods of rotation than otherwise, and can 

 develop into large-girthed stems of considerable marketable 

 value. 



Spruce with Larch This mixture is at first very similar to 

 that of Spruce and Pine, except that, on soils suited to it, the 

 Larch remains permanently predominant. Where, however, 

 the soil is wanting in depth or in mineral strength, and very 

 frequently in low-lying localities, the Larch is apt to be over- 

 taken in growth in height by the Spruce, and then it is hardly 

 profitable to endeavour to retain the former so as ultimately 



