214 A MANUAL OF FORESTRY. 



acquire a greater power of resistance against snow, rime, 

 and wind. In practice they are sometimes delayed, 

 because their execution involves expenditure which may 

 not be covered by the receipts from the sale of the 

 thinned- out material. The financial loss thus incurred 

 may, however, be more apparent than real, as it i& 

 generally more than covered by the favourable develop- 

 ment of the remaining trees. 



ii. DEGREE OF THINNING. 

 A thinning is called : 



" Light," when only dry and suppressed trees are 



removed ; 

 " Moderate," when, in addition, the whole or part 



of the dominated trees is removed ; 

 " Heavy," when also a part of the dominant trees is cut. 



In the present case, where quantity is the object, the 

 thinnings should on the whole be heavy, subject to the 

 special requirements of the species and the preservation 

 of a sufficient leaf-canopy. As the demands on the 

 growing space are very great during the first half of life,, 

 thinnings must then be comparatively heavier than later 

 on; heavier in the case of light- demanding and quick- 

 growing than in that of shade-bearing and slow-growing 

 species ; heavier on good soil than on poor. 



Much depends on the original density of the wood ; 

 hence, direct sowings, and woods resulting from natural 

 regeneration generally require heavier thinning than 

 plantings. 



iii. REPETITION OF THINNINGS. 



Thinnings should be repeated whenever they become 

 necessary. The more energetic the growth, the quicker 



