152 FORESTS, WOODS, AND TREES 
As ash trees approaching maturity stand far apart, the 
volume of timber per acre is small when compared with the 
yield of shade-bearing trees. Few actual measurements of 
well-stocked stands of ash have been made in this country ; 
but it is the yield from thinnings that helps to make the 
returns satisfactory. It is doubtful if the annual increment 
of the volume of ash timber—final crop and thinnings being 
added together—ever exceeds in England over 30 to 40 
cubic feet (quarter-girth measurement). Stands of white 
ash in the United States average at 70 years old, per 
acre, on first quality soils, 5600 cubic feet of timber over 
3 inches in diameter, or an average annual increment of 
80 cubic feet (quarter-girth measurement) per acre. The 
plots which gave these results were, however, fully-stocked 
natural stands on alluvial land, much superior to any soil 
on which ash would be planted in England. Though the 
volume in England is small, it must be remembered that there 
is no wood in which there is less waste than ash, as even 
the earliest thinnings can be used. The faster ash is grown, 
the better is the quality of the timber ; hence the importance 
of selecting for this species the best sites in any planting 
area. 
Oak.—As is well known, there are two distinct species 
of native oak, different in their habitats and in their sylvi- 
cultural requirements. The pedunculate oak needs for its 
proper development great depth of soil, associated with 
a large content of water; while the sessile oak is satisfied 
with a shallower soil containing a lesser supply of water. 
The pedunculate oak originally covered with forests the 
clays, loams, and deep sands of the southern and midland 
counties of England, and is now dominant in the coppice- 
with-standards woods which prevail in these counties. The 
original pedunculate oak forests in the alluvial tracts along 
the great rivers disappeared at an early period. The sessile 
oak is now met with in Wales, in the south-west and north 
of England, in Scotland and Ireland, where it thrives on the 
thin soils which rest on the palaeozoic and igneous rocks. 
