312 BRITISH FOREST TREES 



and makes somewhat unreasonable and unremunerative 

 demands on growing-space for a larger measure of light and 

 air. It cannot therefore as a rule maintain the same periods 

 of rotation as hardwoods, and is generally cut out of forests 

 when the clearings and early thinnings take place. 



Its root-system is not in general deep-seated, but tends 

 more to horizontal than to vertical development, though 

 endowed with great capacity of accommodating itself to the 

 conditions of the soil. On shallow, stony soil the roots 

 are mainly superficial, but, where free play is afforded, 

 strong side roots are formed, which soon ramify at a very 

 moderate depth, and disperse themselves horizontally, 

 ending in many branching rootlets ; the growing-space 

 occupied by the roots is therefore not inconsiderable. On 

 the whole it may be classed along with the birch and the 

 mountain ash as a shallow-rooting species. 



Requirements as to Soil and Situation. In general the 

 poplars need mild situations with a free exposure to light and 

 air. Light, friable, fresh or moist, sand or loamy soil is better 

 suited to them than a wet or tenacious soil, although the 

 black poplar is fond of a limy admixture. Marshy tracts 

 are frequently too wet for them, whilst a stony subsoil is 

 also detrimental to their development. The aspen is the 

 least exacting of them in respect to soil ; it grows in most 

 places, although it can hardly be said to thrive on dry sandy 

 or sour marshy land. It asserts itself on soils of all sorts, and 

 often of very shallow nature, but only attains good dimen- 

 sions and strong reproductive power on such as are not 

 wanting in depth. The moist soils favourable to the growth 

 of the hornbeam, the lime and the white alder are best 

 suited to it ; but it is also found associating itself with the 

 common alder on the moister patches, and with the birch and 

 mountain ash on the drier. Moist, sandy loams and loamy 

 sands, especially if rich in humus or mould, in general 



