TEEES FOR WATER CATCHMENT AREAS 163 



Natural birch woods as a rule contain little timber. Those 

 in Glen Mor were estimated to produce when felled only 

 10 tons of wood per acre, and half a ton of twigs, the 

 latter being used for burning the surface scale from steel 

 plates in foundries. 



The value of birch woods lies in the protection which 

 they may afford to plantations of conifers, lying alongside 

 them at a lower level. With the aid of birch, it would be 

 possible perhaps to raise the timber line 200 to 300 feet 

 higher in many mountainous districts in the British Isles. 

 Any natural scrub or wood of birch in the vicinity of a 

 high-lying conifer plantation should be enclosed, and be 

 carefully preserved as a shelter belt. Birch might also be 

 sown freely over wide bands of ground immediately above 

 the sites of contemplated plantations at high elevations, in 

 cases where the ground could be prepared for the seed 

 cheaply and be enclosed at a trifling cost. 



Birch is also very useful as a nurse tree, in frosty 

 localities and in exposed situations, where damage to young 

 conifers is to be feared ; and it may be planted in advance 

 for this purpose. Thickets of self-sown birch thinned out 

 to five or six feet apart will serve as nurses for spruce 

 seedlings, as the latter species usually succeeds in places 

 where birch is able to regenerate itself freely. Birch 

 can be very cheaply planted by the slitting method. 

 In plantations on good sites and favourable situations, 

 birch is a weed, and should be eliminated as soon as 

 possible. 



There are two distinct species of birch, differing in their 

 demand on moisture in the soil ; and it is a great mistake 

 to plant them indiscriminately. (1) Silver birch {Betula 

 verrucosa), with glabrous twigs, pendulous branches, and 

 very white bark, is the faster-growing and larger tree of the 

 two species. It succeeds in a dry climate, and thrives best 

 on a moderately moist soil, and will not grow on marshy 

 ground or in an undrained peat-moss. It succeeds on chalk, 

 where the other species remains stunted or dies. This 

 species occurs in Strathspey, Deeside, and Tayside, which is 



