SOME SILVICULTURAL ASPECTS AND PROBLEMS OF THE SOIL. 49 



ment will likely prevent us from gaining much advantage from 

 the work, and not only so, but since the methods of soil 

 investigation already in use are to a great extent those of 

 agricultural investigators, and are therefore largely inapplicable 

 to the study of forest soils, methods and apparatus of research 

 must be revised and recast from a purely ecological standpoint. 

 For example, structural soil investigation has been undertaken 

 chiefly along two lines, the mechanical analyses of the soil in 

 which the soil structure is completely destroyed, and from the 

 bricks the style of architecture is deduced, and the determination 

 of porosity, water-holding capacity, and similar properties of the 

 soil in which the structure as it is in the field is broken down. 

 Such methods may be quite valuable for soils regularly mixed 

 up by cultural operations, or even by the activities of the soil 

 fauna of mild forest soils. But for the usual type of coniferous, 

 or even broad-leaved forest soil in the North-East of Scotland, 

 always sour, at least to a slight degree, and usually markedly 

 so, deflocculation and long-continued almost static physical 

 conditions result in a degree of packing and possibly cementing 

 of the soil particles which make mechanical analyses no more 

 useful than superficial ocular examination, and certainly of less 

 value than the time it requires would demand. 



Although the same objections do not hold good with regard 

 to purely chemical methods of investigation, yet it must be 

 granted that the physico-chemical facts determining soil fertility, 

 and controlling the biological interactions of the soil, are as yet 

 scarcely understood. 



For these reasons the investigator of ultimate soil relationships, 

 working from scientific origins, may have for some time no 

 direct point of contact with the practical forester, who is, when 

 all is said and done, not vitally concerned with ultimate factors, 

 but with the actual and total production co-efficient of these 

 ultimates, and is in need of some means by which this pro- 

 ductive capacity of the soil may be estimated, with at least a 

 fair degree of accuracy. 



The provision of such an aid to evaluation of the soil is the 

 chief problem confronting the forest soil scientist. Such a 

 method has been proposed by Mr A. C. Forbes, in the 

 Transactions^ numerical values being given to some of the 

 more striking and obvious factors of locality ; but it is doubtful 

 1 See Vol. XX., Part 2, p. 15S. 

 VOL. XXXVI. PART \. D 



