IMPORTANCE FOR WOOD-PRODUCTION. 51)1 



That humus should have a neutral or basic action on the soil 

 is a necessary condition for the successful growth of most forest 

 trees. The cultivation of beech, silver-fir and hornbeam appears 

 to depend on it. In mountain-regions and wherever the soil con- 

 taining the roots of trees is formed by the disintegration of the 

 subjacent rock (the sub-soil water not being stagnant) the soil 

 has a neutral reaction. The contrary happens in the sandy 

 plains of North Germany and in countries bordering on the 

 Baltic, especially in Schleswig-Holstein [also in extensive sandy 

 heather-tracts in the British Isles. — Tr.] 



If, therefore, humus is to act beneficially on soils, the decom- 

 position of the soil-covering must be moderately rapid and con- 

 tinuous. For then only are those chemical constituents of soils 

 replaced which have been used in plant-growth, whilst, at the 

 same time, a sufficient quantity of litter and humus remains as 

 an indispensable covering of the soil. 



Decomposition often proceeds differently in the different strata 

 of the soil-covering: whilst chemical change ^predominates in its 

 upper strata, the lower strata rather putrefy ; chemical change is, 

 however, the more active agent, especially in localities with a 

 dense standing crop of trees. Although it is difficult to state 

 the exact time required, it may be alleged that for ordinary 

 forest localities, humus is formed in the most beneficial manner 

 when the soil-covering of dead leaves is decomposed in two or 

 three years and that of dead needles in three or four years, the 

 underlying stratum of humus being about a centimeter (one- 

 third of an inch) thick. 



4. Summary. 

 To resume all that has been said in the preceding pages 

 about humus, it must be admitted that it is the chief factor 

 in the fertility of soils. "Whenever the forester has to pro- 

 duce the greatest quantity of w^ood of the best quality, he 

 must maintain continuously the productiveness of the soil by all 

 the means in his power. Of these, none is more effective than 

 preserving humus in the most suitable condition. However 

 abundant chemical nutriment may be in rich soils, it is worth- 

 less, unless the means for rendering it soluble (carbon dioxide 

 and water) are present. A rich soil can dispense with humus 

 better than a poor soil, but in the long ran must fall back upon it. 



