12 ELEMENTS OF SYLVICULTURE. 



Very cold climate ; here among broad-leaved trees 

 we only meet with the birches, mountain ash, service 

 tree, &c., and it is the natural home of the spruce fir, 

 and above all of the larch, and the Cembran and 

 dwarf pines. 



SOILS. The function of the soil with regard to 

 plants is twofold ; it affords them a solid base, and 

 it aids in their nutrition. Forest trees, however, 

 require very little inorganic matter immediately 

 assimilable, and what is more important, the greater 

 bulk of these principles, taken up every year by the 

 trees, is returned to the soil in their leaves and fruit ; 

 it may therefore be asserted that as regards forests 

 the physical properties of a soil are far more im- 

 portant than its chemical composition. 



The chief physical properties of soil are depth, 

 Jiygroscopicity, compactness, and colour. It is the 

 first two that chiefly affect forest growth ; in a deep 

 hygroscopic soil the trees make rapid growth and 

 attain a considerable height ; the latter feature is 

 characteristic, and allows us to infer with certainty 

 the depth or shallowness of a soil. The hygroscopicity 

 of a soil, which is in direct proportion to its compact- 

 ness, is the facility with which it absorbs a greater, 

 or less amount of water, and retains it with more or 

 less force. On the compactness of a soil depends 

 the greater or less ease with which it is penetrated 

 by the roots of plants. The colour of a soil favours 

 or diminishes its aptitude to absorb heat. The best 

 forest soil is one which, besides being deep, is 

 moderately stiff and fairly hygroscopic. 



The mineral composition of the topsoil consider- 



