THINNING. 



Fig. 19. 



of a proportionate number of the stores and trees in the different 

 age-classes corresponding with the rotation of the underwood. 



If broad-leaved trees cannot be thinned out at once (e.g., 

 Beech interfering with Oak, Ash, &c.) they can be ringed or 

 girdled by cutting through the sapwood into the heartwood 

 and left to season on the stump till the next convenient time 

 for removing them. But this cannot be risked with Conifers, 

 on account of the danger from insects. 



Poles and trees to be thinned can best be marked with the 

 scribe (Fig. 19) while in full leaf. It is best to fell and extract 

 the thinnings during winter ; but it 

 can be done in summer, if more con- 

 venient. 



Under our old national system of 

 arboriculture, young plantations, as well 

 as middle-aged and maturing woods, 

 were habitually overthinned, and the 

 trees therefore grew up much rougher 

 and more branching than is now de- 

 sirable; but if a rational amount of 

 thinning be not done, the crops get 

 too thick, and the crowns of foliage too 

 small for healthy growth. The per- 

 centage of the crop that may advantageously be removed at 

 each thinning will vary greatly according to the kind of tree 

 and the age of the crop, the quality of the soil, and the eleva- 

 tion, exposure, and slope of the land ; and it may vary from 

 about 5 to 10 per cent of the standing crop at different ages. 



Thinnings generally begin when the price obtained for what 

 is cut out more than pays the cost of cutting and extraction ; 

 and, of course, the larger this income or partial return from the 

 capital sunk in the plantation is, the less the net cost of a young 

 crop just after a thinning. This tends to induce somewhat heavy 

 thinning ; but, if the woods are to be managed on purely busi- 



