2 So THE FORESTER. December, 



self if exact results are sought. There is he fqund the soil under young Spruce 



one great distinction between water flow- trees to have 2 per cent, and under old 



* ing freely in open channels or pipes of Spruce trees 73^ per cent, greater capacity 



measurable size, and percolating water. than naked soil. These are very instruc- 



The flow of the former is a function of tive figures. 



the square root of the head, while the flow 



of water traversing minute passages varies iuE " b OREST ^loor. 



*fc> 



directly with the head. It is manifest that the character of the 

 Capacity, as previously stated, is the forest floor, i. e., the litter covering the 

 quantity of water which can be introduced ground, must have a marked effect upon 

 into a dry soil. It is usually expressed as the absorption of water. Wo liny found 

 a percentage of the soil volume. The as a result of his experiments that under a 

 total quantity that a soil is capable of im- grass cover there was 50 per cent, less 

 bibing is termed its maximum capacity. percolation than in naked soil. He found 

 This quantity is divisible into two parts : a litter of Oak leaves to pass 42 to 74 per 

 the one removable by drainage, the other cent, of the rainfall, Spruce litter 46 to 

 by evaporation. This latter part is again 78 per cent., Pine needles 52 to 69 per 

 sub-divisible into two parts, one brought cent., Moss 39 to 53 per cent. The vari- 

 to the surface by capillary action and there ations are due to varying thickness of 

 evaporated ; the other almost permanently cover. The shallower the cover the less 

 retained within the soil, requiring for its the soil imbibed, for the obvious reason 

 removal long continued applications of that the water was presented to it too 

 heat. This part is termed hygroscopic quickly. Again, considering the Rotham- 

 moisture. sted tests, which gave the percolation of 

 German authorities have determined the bare soil at from 45 to 473^2 per cent, of 

 maximum capacities of various soils to the rainfall, it will be seen that ordinary 

 range from 463^ per cent, for quartz sand forest litter will pass more rainfall than 

 to 7/2 per cent, for humus, and the the earth ordinarily imbibes. Conse- 

 minimum capacity or water remaining quently the cover will remain in a state 

 after gravitation to range from 17 per of saturation for a greater or less period 

 cent, to 49 per cent. Of the minimum of time during which it will protect the 

 capacity the portion retained as hygro- ground from evaporation. A soil cover- 

 scopic moisture has been determined by ing of humus, however, would allow little 

 Longbridge, of the California Experiment water to pass to the soil beneath. It 

 Station, to range from less than 1 per cent. would be beneficial in lessening the force 

 for sand to 14^2 per cent, for clays, these of storm water, but otherwise would work 

 percentages being referred to maximum a loss to ground storage. Ebermayer says 

 capacity. The wide range in the figures that besides clay it is especially humus 

 serves to illustrate the necessity of experi- which imbibes almost all precipitation and 

 menting directly with any soil under con- gives up little water to the ground below ; 

 sideration if exact data are required. and he adds that if the earth were covered 

 Of the different capacities the hydraulic by a humus soil of one meter in depth, 

 engineer is more particularly concerned in subterranean drainage would be so slight 

 that which relates to the quantity that may that springs would be scanty and continu- 

 be drained out; on the other hand, the ar- ously flowing springs absent, 

 boriculturist is much interested in the The forest floor is a most important 

 amount of capillary water from which factor in retarding storm-water and pro- 

 plant life largely draws its supply. An tecting the earth from erosion. This is 

 authority on effects of forest cover (Dr. particularly true on steep mountain slopes. 

 E. Ebermayer), found that, except for the The destruction of forest litter by fire, 

 top layers, unshaded soil had more sheep, or deforestation is little short of a 

 capacity than shaded soil. Taken as a national calamity. Each rain washes 

 whole, however, for a depth of 32 inches away tons upon tons of loam, sand and 



