ON PLANTING DISTANCES FOR CONIFERS. 21 



the close wood, the accumulation of organic material in the soil 

 goes on. Unless this can be utilised later on in life by the 

 wood, its accumulation has little value. It can only be fully 

 utilised by the free admission of oxygen, which enables the soil 

 bacteria to break up the organic compounds into food available 

 to the trees. This admission of oxygen is secured by thinning, 

 so that it is only indirectly that it can be claimed as an 

 advantage of open planting. At any rate in a wood, closely 

 grown but left unthinned, the disadvantage lies in the fact that 

 the stores of food in the humus are not used. Rather are they 

 dissipated and lost after the wood is clear felled. In open woods, 

 both in early life and after, accumulation and decomposition go 

 on simultaneously with benefit to the trees. The ideal state of 

 affairs is accumulation of humus in early youth under a close 

 canopy, and decomposition in the later stages under a more 

 open canopy. 



10. The crowns are much larger in the open woods, and the 

 light is utilised to the fullest extent. The leaf-fall is also 

 heavier. 



11. In too close stands an over-production of raw-humus may 

 have a detrimental effect on the soil conditions. After what 

 has been said above, it is only necessary to point out that this 

 is due, amongst other things, to a deficiency of air. As a 

 result bacterial action is slow or wanting. 



12. As a rule, the more densely grown the wood the smaller 

 are the lower branches. The importance of this is apt to be 

 exaggerated with certain species. The more robust individuals, 

 for example, in a closely-grown Japanese larch or Douglas fir 

 plantation, usually possess large lower branches. It is an 

 undoubted fact, however, that these branches are much less in 

 Norway spruce and Sitka spruce, and that, as a result, the 

 timber in the first cut is cleaner and more free of large knots. 

 Climatic conditions, as explained below, have probably a most 

 important influence on branch production. 



13. The number of thinnings available for removal from the 

 closely-grown plantation is greater than from the openly-spaced 

 wood. At the same time there is also a greater choice of stems 

 for the final crop. 



In the second period, the advantages would seem to be more 

 with the more widely-spaced woods. Planting at distances of 

 3 feet to 4 feet produces a quite unnecessarily intense struggle 



