Xll APPENDIX. 



The first factor that must be suitable is the soil, that is to say 

 the chemical, physical and biological conditions of the soil must 

 all be favourable. Every forest soil probably 'contains the limited 

 quantities of nitrates, phosphates, lime and potash necessary to 

 plant life. The availability of these chemical substances will 

 largely depend on the physical properties of the soil. Excess of 

 such substances as humic acid in the soil is very prejudicial to 

 plant growth, but such excess is due to physical causes which can 

 be overcome by good husbandry. Adverse physical soil conditions 

 may be ameliorated, stiff clay will be improved by the mainten- 

 ance of a close forest canopy over a series of years and the con- 

 sequent admixture of humus with the soil followed by suitable 

 cultivation. Similarly a light sandy soil can be improved by the 

 natural adding of decaying .vegetation which will increase its 

 water holding capacity. 



If suitable physical conditions cannot be obtained by the 

 proper manipulation of the canopy, then more drastic steps must 

 be resorted to and the surface soil stirred up to produce a good 

 tilth and to amalgamate the humus with the mineral soil. Final- 

 ly in order to obtain abundant natural regeneration the bacterial 

 flora of the soil must be prolific and the process of nitrification 

 active. A soil in good heart will naturally be well aerated and will 

 contain an active bacterial flora. Given active nitrification in the 

 soil, obtained no matter how, natural regeneration presents no 

 difficulty. Henrik Hesselman has shown in the reports of the 

 Swedish Institute of Experimental Forestry, that a lively nitrifica- 

 tion in the ground is essential to profuse reproduction. His 

 researches have shown : 



(1) In the fairly dense mixed coniferous forests of central 



Sweden, where the ground covering consists mainly 

 of moss, clear cutting, shelterwood cutting or merely 

 chequerboard cutting can produce lively nitrification. 



(2) The preparation of the soil with the Finnish plough or 



any other machine that causes a mixture of the 



