6o 



Studies in Forestry 



[CHAP. III. 



rapid growth, and Spruces and Silver Firs as relatively slow in 

 initial development. 



These results show that, in a general way, the rate of growth 

 in height during the earlier stages of tree-life coincides with 

 the demands made by the species on light and growing-space. 

 Some species, like Douglas Fir, Larch, and on good soils 

 Pines and Birch, maintain the advantage gained ; but others, 

 like Ash, Maple, Sycamore, and Aspen, are caught up in 

 growth and overtopped by Spruce, Silver Fir, Beech, and Oak, 

 whose vigour increases on their attaining the pole-forest stage of 

 development. The duration of active growth in height in any 

 given species depends to a great extent on the quality of the 

 soil and situation; but, coeteris paribus, it is maintained longer 

 by Larch and Firs than by Pines among conifers, and longer 

 by the sessile Oak, Elm, and Beech than other species among 

 broad-leaved trees. The average heights (in feet, and ap- 

 proximate only) of some of our more common forest trees, on 

 soils of merely average quality for each different kind of tree, are 

 about the following in well-managed woods of normal density : 



It is at once perceptible from these figures how careful the 

 tending will require to be in mixed crops between the fortieth 

 to sixtieth years, and even earlier on soils of inferior quality ; 

 for wherever light-demanding species are overtaken by shade- 

 bearing species they must be killed off in the struggle for 

 supremacy, unless favoured to a greater or less extent during 

 the special operations of tending. 



