180 THE INCREMENT. 



generally reaches its maximum during the first five years of 

 the tree's life, frequently in the second or third year. Deodar 

 shows a height growth similar to that of spruce, though some- 

 what quicker during early life. S&1 shows, as far as is known 

 at present, a remarkably even rate of height growth up to an 

 age of 80 or 100 years. 



Coppice shoots show, generally, the greatest height growth 

 during the first few years of their existence ; the rate of 

 increment begins to fall off early, nor do such shoots, rare 

 cases excepted, reach the same ultimate height as seedling 

 trees. 



The comparative height growth of different species has been 

 dealt with at p. 163 of Volume I. of this Manual. 



The lateral increment of the trunk of a tree, i.e., diameter 

 or sectional area increment, depends on the surface of the leaf 

 canopy and on its activity. Hence, free growing trees increase 

 more rapidly in diameter than those grown in dense or crowded 

 woods. At the same time the position of the leaf surface is 

 of importance. Trees with a crown coming close to the ground 

 are comparatively more tapering, while those with the crown 

 reduced to the upper part of the stem show a more cylindrical 

 shape. The form or shape of the stem depends therefore on 

 the distribution of the crown. If, with advancing age, the 

 crown of trees in crowded woods moves higher up the stem, the 

 difference in diameter increment between the lower and upper 

 part of the stem decreases, and this is accompanied by what 

 may be called the "form increment"; in other words, the 

 tree becomes less tapering. The forester expresses this, as 

 explained at p. 36, by the " form factor," or the coefficient by 

 which the volume of a cylinder of the same base and height as 

 the tree must be multiplied, in order to obtain the volume of 

 the stem of the tree. 



It has been stated, at p. 38, that in practice only the form 

 factors based on a measurement of the base at height of chest, 

 or 4 feet above the ground, are used, and at p. 39 the form 

 factors for the following trees were given : 



