632 JOURNAL 'OF FORESTRY 



fauna. The soil particles under forest cover are being continually 

 moved and stirred up often to considerable depth. The species com- 

 posing the forest, as well as the character of the stand, have a decided 

 influence upon the degree to which forest soil is maintained in a porous 

 and permeable condition. 



Forest soil is very much more permeable to water than unprotected 

 soil. Even on the steepest slopes forest soil absorbs the heaviest rain- 

 fall almost immediately. Soil with a dense covering of sod is very 

 slightly permeable. On protected forest soil rain water flows off under 

 the ground but on treeless soil, especially after heavy rain, or rapid 

 thawing of snow, the w^ater is discharged mostly on the surface. On 

 steep sodded slopes the run-off was found to be the greatest. Water 

 flows much more slowly in the ground than on it and a great part of 

 the water does not usually run off at all but is stored in the interstices 

 of the soil. 



The whole explanation of the favorable effect of forest cover upon 

 streamflow lies thus in the greater porosity and permeability of the 

 forest soil. 



The Emmental Experiment Station has discarded an opinion long 

 held by many prominent investigators such as Ebermayer, Wollny, 

 Ney, Henry, and others, that the great water retaining power of the 

 forest soil is due mainly to the great retentive capacity of the leaf 

 litter and moss cover. The experiments have conclusively shown that 

 raw humus and moss cover have had a very unfavorable effect upon 

 the water regimen. Many evidences of damage from floods in for- 

 ested regions could be directly traced to accumulations of raw humus 

 in the forest. It is true that raw humus and moss absorb large quan- 

 tities of water but give off very little of it to the soil, and when once 

 saturated they cause the rainfall to flow off on the surface. It was 

 found that on a thick cover of pine needles and deep leaf litter, the 

 rain water ran off very rapidly on slopes of any steepness. In a period 

 of drouth, on the other hand, raw humus and moss cover did not 

 permit light rainfall to reach the ground at all. On a whole, raw 

 humus and moss cover act upon the regime of streams like peat and 

 moor soils. 



The moisture content of the soil under forest cover and in the open 

 follows different courses. In the open the soil because of its greater 

 compactness, contains a greater amount of capillary water than forest 

 soil. The forest soil, on the other hand, contains much more ground 

 water. The moisture content of the superficial layers of the unpro- 



