146 



FOREST INFLUENCES. 



equal to 54 cm. precipitation, which is equal to three-fifths of the mean 

 annual precipitation at the station, of which the author presumes not 

 more than 30.5 cm. are used for an averajie crop of agricultural grains. 



Coming- now to the influence which a forest cover may have upon the 

 water capacity of the soil, Ave have to record the results of Dr. E. Eber- 

 raayer, who has investigated the water capacity of a heavy loam soil, 

 both protected and unprotected by a forest cover. 



The following table containsthe measured amounts of water contained 

 in such a soil under a forest of spruce, twenty-five, sixty, and one hun- 

 dred and twenty years old, and a naked soil at IG inches (40 cm.) and 

 32 inches (80 cm.) depth. 



Water contents of a loamy sand; results hif seasons expressed in percentages of the iveight 



of the soil. 



These figures show that a loam soil under forest cover is apt to be 

 drier in the depth of the root region, and that at all seasons, than in the 

 open field at the same depth, less so under an old and scattered growth 

 than under a younger growth or thicket. 



A repetition of these experiments, in which various depths from the 

 top to 32 inches were included, gave during two years the following 

 averages of water cai^acity, expressed in percentages of the Aveight of 

 the soil: 



Averages of water capacitg, expressed in percentages of the weight of the soil. 



Ebermayer combines the values for depths from inches down to 32 

 inches, and then concludes that the forest soil is less moist, due to the 

 transpiration of Avater by plants. This conclusion is, however, not at 

 all warranted. For if one combines the figures f\)und in all the strata 

 from the top to 3 inches down, they figure as follows: Sx^ruce 25 years 



