12 Some Problems of Re-afforestation. 



species, like oak, spruce, silver fir, &c. If the young plants 

 have to contend with strong herbage or, indeed, with any 

 prejudicial factor, such as rabbits, or insects greater density in 

 the stocking is justified, if only to discount a higher death rate. 

 Trees, again which readily lose their side branches, e.g., larch, 

 need not be crowded to the extent necessary with species, e.g., 

 spruce, whose lower branches must be killed when very young 

 if the stems are to clean themselves properly. For general 

 purposes, and assuming the trees set out in triangles, a distance 

 of 4 ft. from plant to plant may be taken as the standard, which 

 means, theoretically, 3,144 trees per acre. An additional foot 

 of interspace reduces the number of trees to 2,012 per acre, and 

 such wide planting is quite justifiable in the case of good 

 ground and a quick-growing species, where small thinnings 

 are of low value. 



In the past the great majority of woods have suffered from 

 over-thinning, nor has it been sufficiently recognised that a 

 degree of density right for one species may be wrong for 

 another. The main results of over-thinning are (1) the 

 growing stock is not at its maximum, and consequently the 

 highest annual increment cannot be secured, and (2) the trees 

 are encouraged to retain their branches, and this means shorter 

 boles and coarser and more knotty timber. Attention has, in 

 many cases, been given too much to the individual trees, 

 forgetting that in commercial forestry it is the yield of the 

 wood as a whole, not the vigour of the single trees, that deter- 

 mines success. 



Where woods are primarily designed as shelter- belts a 

 degree of thinning that would be excessive under other cir- 

 cumstances is not only justifiable but necessary. Here the 

 intention is to provide shelter to fields lying to leeward, and 

 this object will be better secured by trees with low-reaching 

 branches than by clean stems with small crowns confined to 

 the upper third or fourth of their length. Moreover, such 

 trees, being better balanced and better rooted, are not so liable 

 to be blown down or broken over, and a shelter-belt, as its 

 name implies, is generally formed in an exposed situation 

 where stability is vital to success. Similarly along the wind- 

 ward side of a wood, thinning should begin earlier and be 

 carried further. On that side of the wood, too, deep-rooted 

 species and those which, given space, will produce and retain 

 strong side branches should be employed. Such trees are the 

 beech, oak, silver fir and Corsican and black Austrian pines. 

 It is perhaps not generally recognised that the safety of a wood 

 in regard to gales is largely dependent on the outer fringe of 

 trees, and especially on the outermost row. The marginal trees 

 should be encouraged to produce strong low-reaching branches 



