BRITISH FOREST TREES 39 



A comparison of this table with that (on p. 26) exhibiting 

 the requirements of the different species of forest trees as 

 to light, shows that in a general way the light-loving trees 

 are those also of quickest growth in height. 



Some species, e.g. larch, and under favourable circum- 

 stances Scots and Weymouth pines and birch, maintain the 

 advantage thus early won even after they have entered into 

 the pole-forest stage, when growth in height is most active ; 

 other species, e.g. ash, maple, aspen, though still active in 

 growth, do not maintain their early promise, but are over- 

 taken and topped by species like the spruce, silver fir, beech 

 and oak, which display increased vigour on reaching the 

 pole-growth stage. Continuation of growth in height at 

 the more advanced periods of life is dependent on the 

 influences of soil and situation, but cateris paribus is main- 

 tained longest by spruce, silver fir, and larch, which naturally 

 incline towards growth in height rather than to branch 

 development. Among the broad-leaved deciduous trees 

 the sessile oak, elm, and beech retain the power of growth 

 in height longer than other species, which early become 

 rounded off in the crown on its cessation. 



Adopting the graphic method, introduced by G. Heyer, 

 the table on p. 38 showing the rate of growth in height can 

 be represented by co-ordinates (see table on next page), the 

 ordinate being the height attainable, and the absciss the age 

 at which it is obtained. 



Elevation, exposure to winds, and soil fertility all exercise 

 influences on growth in height, which may be summed 

 up in the short statement that the more suitable the soil and 

 situation are for any particular species of tree, the more 

 active and energetic will be its growth in height. Deep, fresh, 

 light soil, rich in humus, is more favourable than binding 

 soil of great mineral strength ; high elevation above sea-level, 

 or exposure to winds, interferes with the natural development 



