200 BRITISH FOREST TREES 



their crowns, a considerable degree of sunlight is allowed to 

 play over the soil, and the fall of leaves is both too light, and 

 of too poor a humus-producing quality to conserve the pro- 

 ductive capacity of the soil, which, losing both its moisture 

 and its fertility, can no longer give generous supplies of 

 nutriment to the timber crop. Under favourable circum- 

 stances a self-sown growth of hornbeam, hazel, and other 

 minor trees and shrubs finds its way into the woods and forms 

 undergrowth protecting the soil against insolation ; but 

 too often the oaks are apt to become stag-headed and sickly, 

 and to show a growth of mosses or lichens on their boles, in 

 place of exhibiting a clean healthy bark. On soils of merely 

 average quality, therefore, experience has shown it to be 

 advisable to make a partial clearance of the oak at about 

 seventy to ninety years of age, by which all individuals not 

 likely ultimately to yield really good timber are removed, and 

 to underplant the remaining selected trees with some soil- 

 improving species, generally the beech, but also hornbeam, 

 silver fir, or spruce, according to the nature of the soil. 



As all species of trees protect the soil during the early stages 

 of growth, whilst they form close canopy, there is not as a rule 

 any danger of deterioration when pure forests of oak coppice 

 are formed on soils of average quality, and in many parts of 

 Germany this form of sylvicultural treatment has taken place 

 uninterruptedly for centuries on favourable situations. For 

 oak coppice, the most favourable localities are those w r ith 

 long periods of annual active vegetation, with warm, sunny 

 exposures, and moderately deep, loamy soils ; even where a 

 fertile soil seems shallow on the hill-sides, it is still sufficient 

 if the subsoil is fissured so as to admit of the penetration of 

 the root-strands in search of soil-moisture. Marshy situa- 

 tions, or sandy soils poor in loam and deficient in humus, 

 are not localities suitable for this kind of sylvicultural crop. 

 When the area is sufficiently stocked with stools, and the fall 



