184 WATER AND FOREST. 



ested in the amount of capillary water from which plant life largely 

 draws its supply. The capacities are interwoven and the experimental 

 determination of the moisture coefficients of local soils will be a fruit- 

 ful field for forestry students. To return to capacities. An author- 

 ity on effects of forest cover (Dr. E. Ebermayer) found that except for 

 the top layers unshaded soil had more capacity than shaded soil. 

 Taken as a whole, however, for a depth of thirty-two inches he found 

 the soil under young spruce trees to have 2 per cent., and under old 

 spruce trees 7.6 per cent, greater capacity than naked soil. 



It is manifest that the character of the forest floor, the litter cov- 

 ering the soil, must have a marked effect upon the absorption of 

 water. Wollny found, as a result of his experiments, that under a 

 grass cover there was 50 per cent, less percolation than in naked soil. 

 He found a litter of oak leaves to pass 42 to 74 per cent, of the rainfall. 

 Spruce litter passed 46 to 78 per cent. Pine needles, 52 to 69 per 

 cent. Moss, 39 to 53 per cent. The variations are due to varying 

 thicknesses of cover. The shallower the cover the less the soil re- 

 ceived. This may be attributed to greater rate of evaporation with 

 the shallower covers. 



As previously stated, the Rothamsted tests gave the percolation 

 of bare soil at 44 9-10 to 47 1-2 per cent, of the rainfall. It will be 

 seen, therefore, that ordinary forest litter can pass more rainfall than 

 the earth ordinarily imbibes. Consequently the cover will reniain 

 wet for a greater or less period of time, and during that period save 

 the soil from evaporation. A soil covering of humus, however, would 

 scarcely allow any filtration to the soil beneath. It would be bene- 

 ficial in lessening the force of storm water, but otherwise would work 

 a loss to ground storage. 



Ebermayer says that besides clay it is especially humus which 

 imbibes almost all precipitation and gives up little water below; and 

 adds, that if the earth were covered with a humus soil of one metre 

 in depth subterranean drainage would be so slight that springs would 

 be scanty, and continuously flowing springs absent. 



The forest floor is a most important factor in retarding storm 

 svater and protecting the earth from erosion. This is particularly 

 true on steep mountain slopes. The destruction of forest litter by 

 fire or de-forestation is little short of a calamity. Each rain washes 

 away tons upon tons of loam, sand and rocks to cover up the lower 

 lands. A double disaster. The fertile soil of the higher lands is 

 destroyed, the fertile soil of the lower lands buried. 



