INCREMENT, 99 



Growth in Height is most energetic during the pole-wood 

 stage of development, but begins to fall off when trees require an 

 increased individual growing-space enabling them to expand their 

 crowns. Hence, although light -demanding trees are usually 

 more rapid in early growth than shade - enduring trees, yet 

 the latter generally continue longer in active growth in height. 

 Conifers generally and in particular Larch, Spruce, and Firs, 

 less so Pines have a more continuous tendency to upward 

 growth than broad-leaved trees. But light- demanding trees 

 require thinning earlier and oftener than shade-enduring kinds, 

 and this necessity for. lateral expansion of course exerts an 

 unfavourable influence on the continuation of good growth in 

 height. For any one kind of tree, however, the growth in 

 height depends to a great extent on the quality and especially 

 on the depth of the soil, and on the amount of thinning that 

 has taken place ; because thinning, by encouraging growth 

 laterally, tends to limit the height-growth. 



Growth in Girth is more or less proportional to the height 

 and the breadth of the crown, the quantity of foliage, and 

 the intensity of the sunlight ; and it attains its maximum when 

 the crown of foliage is largest in proportion to the girth of the 

 stem. Thus there is always a very noticeable increase in the 

 width of the annual rings formed just after a thinning has 

 taken place, this increase being due to the larger production of 

 foliage ; and the total increment in wood for any given soil and 

 situation depends mainly upon the amount of foliage and the 

 intensity of the sunlight operating upon it. 



As growth in height is at first, at any rate stimulated by 

 keeping the woods close, and as growth in girth is stimulated 

 by free thinning, the largest increment can only be obtained by 

 trying to strike a suitable mean between not thinning sufficiently 

 and overthinning. Hence, for every kind of tree-crop and for 

 every stage of its development, there is, for any given quality 

 of land, a normal density of crop tending to combine a good 



