K.—BOTANY 201 
_ of diameter increment. 'The quality of timber depends to a large extent 
upon uniformity in breadth of the year rings and the texture and fibre of 
the wood. ‘This can only be obtained if the growth of the tree itself is 
uniform and sustained. Hence in this latter half of the rotation attention 
must be directed to the crowns and roots of the trees. A gradual removal 
of certain trees and opening up of the canopy gives the crowns of the 
remaining trees more light and room to expand, and this means increased 
food production. These cuttings may be called ‘light increment cut- 
tings,’ in contradistinction to ‘ thinnings,’ from which they differ in regard 
to their influence on the biology of the stand. The more open growth 
under light increment treatment means fewer trees at maturity, say 
160 per acre, but individually they are of greater volume and collectively 
of not less volume than would have been produced by a larger number 
of trees in closely crowded crown competition. The more open stand 
necessitates the retention of some kind of undergrowth or, more commonly, 
underplanting for soil cover and preservation. ‘l'his method has been suc- 
cessfully practised in Denmark in the case of beech, oak, pine and spruce. 
Under the old system of dense canopy preservation, the intermediate 
yield in thinnings was about 25 per cent. of the final yield. Under the 
light increment treatment the thinnings may amount to 20 per cent. and 
the light increment cuttings to 50 per cent. of the final yield. ‘That means 
in the latter case we have 75 per cent. against 25 per cent. in the former ; 
and if we assume, as we are entitled to, that the value of the material 
removed in light increment cuttings is greater per unit of measurement 
than that of thinnings, and at the same time if we keep in mind the fact 
that the volume of the final yield is the same in both cases, with the 
balance in favour of quality in the case of light increment treatment, it 
will be seen that the treatment increases the yield per acre by well over 
50 percent, ‘The material removed by the light increment cuttings, from 
the fiftieth year onwards, would be clean grown and straight, and would 
yield all sizes required for telegraph poles, for which the demand has 
always been high. ‘The trees of the final crop would easily be of sleeper 
size—that is the most all-round useful and valuable size for mature timber. 
If this can be done in Denmark, why should it not be possible in our 
equally favourable if not more favourable climatic and soil conditions ? 
All the problems which arise in regard to the care and treatment of 
young, middle-aged and maturing stands of trees, are subjects of the 
study of stand biology, and that system of silviculture which makes the 
fullest use of the external factors of growth, in combination and individ- 
ually, will achieve the best results in the end. The old system of preserving 
dense, uniform, unbroken canopy was unnatural and made it impossible 
to utilise to its full advantage the important growth factor, light. 
In the primeval forest, loss and replacement is constantly going on. As 
each veteran disappears it is replaced by hundreds of seedlings which 
strive and struggle among themselves and against surrounding hindrances 
to reach the light. The struggle is a prolonged one, and many seedlings 
and saplings are killed off in the process. Still, Nature works cheaply if 
slowly, and if we can make use of the free gift she offers in the way of 
natural regeneration, it would be an obvious gain. Nature has produced 
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