CHAP, v.] Soil and Situation 101 



levels the Oak is one of the species thriving best in mixed 

 forests of broad-leaved trees. Natural regeneration is easy on 

 loamy soils when a good seed year comes round ; but, as good 

 seeding or mast-years can not be depended on in crops on 

 loam, it is best to sow seed procured from elsewhere rather 

 than to risk deterioration of the soil from insolation after 

 once the preliminary fellings have been made. 



As the fertility or productive capacity of soils is neither 

 dependent on, nor mainly proportional to, the mineral richness 

 of the rocks from whose decomposition they are formed, no 

 hard and fast classification as to their mineral strength is 

 possible. It can only be said that, in general, clayey soils are 

 slow in forming humus and giving nutrients to tree-life, whereas 

 limy soils decompose organic matter rapidly and stimulate 

 tree-growth, and that intermediate positions between these two 

 groups are occupied by sandy and loamy soils, except when 

 the sands are deficient in soil-moisture. 



All soils are improved by an admixture of humus to a mode- 

 rate extent. It not only adds depth to the land, but, being 

 of a strongly hygroscopic nature, also condenses and retains 

 atmospheric moisture ; whilst, owing to its low conductivity, it 

 protects the soil against evaporation. It is also directly active 

 in aiding the continuous decomposition of the soil by means 

 of the carbonic acid set free during the process of decomposi- 

 tion. It modifies all extremes of physical properties in soils ; 

 and though not an absolute necessity for the production of 

 woodland crops, yet it is of inestimable value in stimulating 

 the action of soils, no matter of what geognostic origin. 

 Indeed, as Gayer remarks 1 , there can be little doubt that 

 * humus forms the most important factor relative to tree- growth, and 

 is a priceless treasure as regards the production of woodland crops? 

 And the beneficial influence it exerts on the aeration of soils 

 is by no means its least important quality. When soils contain 

 20 % or more of humus they are termed humose ; fertile silt left 

 1 Waldbau, 1889, p. 27. 



