226 A MANUAL OF FORESTRY. 



allowed to grow up into trees ; in other cases it is only 

 treated as a soil-protection wood, and is periodically 

 coppiced. Beech makes the best underwood, as it bears 

 much shade and improves the soil more than any other 

 species. Silver Fir comes near it. Hornbeam is best in 

 frost localities. Spruce should only be used in fresh 

 localities, as on dry soil it may cause the overwood to 

 fall off in growth. 



Where the underwood is permitted to attain the size 

 of timber-trees, it is either cut with the overwood, or 

 the latter may be retained for two rotations of the 

 underwood, thus producing specially large timber. 



A few remarks on the tending of the more important 

 species will further illustrate the method. 



i. OAK AS OVERWOOD. 



A fully stocked Oak wood is, when the time for 

 thinning has arrived, thinned rather heavily at frequent 

 intervals, say every 5 to 10 years according to the 

 locality; during these operations all trees with a ten- 

 dency to lag behind are removed, as well as ill-shapen 

 and diseased trees. At the age of 40 to 60 years, 

 according to circumstances, a specially heavy thinning 

 is made and the underwood started, Beech being best 

 for the purpose. When the underwood has established 

 itself, say 10 to 15 years afterwards, another heavy 

 thinning is made, by which the remaining trees are 

 isolated. Subsequently more thinnings follow, at 

 moderate intervals, in the same degree, as the Oaks 

 develop and threaten to close up again. 



It is estimated that in this way about 50 Oak trees 



