1 8 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



Dealing with these results so far, we can say that close 

 planting is preferable : — 



(a) On poor soil, where humus production is hastened by 

 the heavier leaf-fall, and where failures are likely 

 to be most frequent. 

 (d) On ground with a heavy vegetation. 



(c) Where smaller plants or more slowly-growing species 



are used. 



(d) Where the production of branch-free material is of the 



utmost importance. 



Open planting is permissible : — 

 (a) On more fertile soils. 

 (d) Where the vegetation is not heavy. 



(c) When larger plants or more rapidly-growing species are 



used. 



(d) Where very clean, branch-free stems are not absolutely 



essential. 



Silviculturally, therefore, during the period of formation, it 

 would appear that close planting is more advantageous, on 

 poorer soils especially. 



Let us now consider the effects of planting distance in that 

 period of the history of a wood after the canopy has closed. 



I. The competition between individuals begins earlier, and is 

 more severe in the more closely-planted wood. The degree 

 of competition also varies according to species, e.g., Scots pine, 

 Douglas fir, larch, and Japanese larch soon sort themselves 

 out into stem-classes. Those trees which either have greater 

 individual strength, or have been more fortunate in their 

 treatment during the planting operation, or have been lucky 

 in the site selected for them, shoot ahead, and year by year 

 increase their advantage at the expense of the less fortunate 

 trees. Other species, and especially Norway and Sitka spruce, 

 do not thus sort themselves out, except perhaps on ground 

 of a very variable nature, but all the trees grow up together, 

 hold each other back, and have a detrimental effect on the 

 whole wood. 



2. After a definite period, the number of dead and dying 

 stems in the more closely-planted wood, is considerably higher 

 than in the open plantation. This is of great importance 

 pathologically, and in the case of larch, the general health of 



