TREES FOR WATER CATCHMENT AREAS 153 
It is more a tree of the hills than the other species, 
ascending in the Pennines to 1000 feet. It grows fairly 
well on sandy and gravelly soils at moderate elevations. 
Oak is a deep-rooting species, which makes poor growth 
on shallow soils. It succeeds best in good loam and in deep 
alluvial ground. It will grow on stiff clays, but not at 
a fast rate. It bears inundation well. Requiring con- 
siderable warmth, oak becomes stunted at high elevations, 
and succeeds better on southern than on northern aspects. 
Oak, once it has passed the young stage, needs much 
space and light, and its rate of growth on all but the best 
and deepest soils is slow. It is late in forming heartwood, 
and its thinnings are of little value. The tree takes many 
years to mature; and when it is ripe for felling, usually in 
this country at 100 to 120 years, there are comparatively 
few stems to the acre. It can readily be seen that its 
cultivation holds out little inducement to private land- 
owners, as the money return of an oak plantation is usually 
less than 2 per cent and payable to one’s heirs. Oak 
should nevertheless be planted in suitable situations by the 
State and by Municipalities, who are bound to provide for 
the future needs of the community. No wood can replace 
that of oak. It is indispensable, as it combines every good 
quality, strength, size, durability, and lightness in an un- 
common degree. In lowland districts, where the soil is 
deep enough, plantations in which oak forms a considerable 
percentage are advisable on land set apart for afforestation. 
It should never be planted pure, on account of its inability 
to protect the soil once it has reached the pole stage. A 
mixed wood of oak and beech, the latter in a proportion 
varying from 10 to 30 per cent, will, it is well known, 
produce a considerably greater volume of timber than if 
the oak were grown by itself. Larch may also be used as 
a nurse on account of its early thinnings, and on good oak 
soil the mixture of oak, beech, and larch will be successful. 
On clay soil, oak and hornbeam can be tried. English 
elm, chestnut, and ash may also be planted in suitable 
spots in any plantation, of which the main components are 
