SOME SILVICULTURAL ASPECTS AND PROBLEMS OF THE SOIL. 39 



such soils, and they become almost useless not only for agri- 

 culture but for forestry as well. Such types of humus would 

 give rise to sour, acid, and finally peaty soils. 



That the construction of a forest practice based upon a 

 sound scientific study of the soil is necessary does not require 

 to be laboured. Past papers in the Transactions have occasion- 

 ally insisted upon this, many have at least indicated the 

 necessity, while in at least one (W. G. Smith) ^ the relative 

 unimportance of local climatic as compared with edaphic 

 variations has been specially pointed out. 



Since the principles of agricultural soil management are 

 more or less familiar to all having any acquaintance with rural 

 science, it is perhaps reasonable to compare and emphasise 

 the differences existing between the soil as an agricultural unit 

 and as a silvicultural unit. 



Almost all agricultural plants are such as would be found 

 growing naturally in mild, mesophytic loamy soil conditions — 

 neither very sour nor very limy, neither very wet nor very 

 dry, neither very light nor very heavy, with a fair admixture 

 of well-decomposed humus, and having, as such soils usually 

 have, a good supply of mineral nutrient salts, that is to say, 

 a normal soil. In a densely peopled country like ours with a 

 long agricultural history, practically all soils remotely approxi- 

 mating to this type have been devoted to agriculture, so that 

 taken as a whole, soils available for afforestation are extreme 

 types, and not only exhibit differences at the present time but 

 always have been in some way distinct, otherwise they would 

 have fallen like the adjacent fields. And corresponding with 

 this variation in forest soils there is a great variety in crop 

 species as regards ability to thrive on these soil types. 

 Compare Maritime pine and beech, alder and birch, Corsican 

 pine and oak, each one of the pairs being adapted to growth 

 under more or less extreme conditions of the soil factors 

 mentioned above. 



Apart from this incidental difference in the soil itself, there 

 lies a still more fundamental difference affecting the whole of 

 the methods of practical application of physiological principles 

 in the two subjects. This is the great difference in the time 

 required for the maturity of the respective crops. The crop 

 of the farmer becomes convertible into money, and yields its 

 ^ See Vol. xxiv., Part I, p. 12. 



