64 



BULLETIN 1105, U. S. DEPARTMENT OF AGRICULTURE. 



Table 17 and Figure 11 show a decidedly higher moisture con- 

 tent within the area in which the action of tree roots has been 

 eliminated. These diifferences are especially significant during the 

 critical period from June 15 to July 15. In the 6-inch samples 

 the contrast is not so striking, on account of direct evaporation, as 

 explained above; but the 12- inch samples are without exception 



Depfh 6 Inches 



Z2.00 



u 

 u 



^ 1.60 



PrecfpitaKon Cinches') 















t 



*, 







U 

 fl. 

 1.20 









•. 







U .60 



i 



, 



• 

 • 



\ 



\ 



* 



D 



h AO 



* 



*, 



* 



• 

 « 



°. 



\ 



/ 



in 

 o 



■c 



Jll 



m«** * 



"rtrt 



*•••» 



**•' 



.* 



Depth 12 inches 



JUNE JULY AUGUST SEPT OCT- 



Pig. 11. — Effect of cutting upon soil moisture, 1920. 



much higher near the fallen trees. In the area occupied by the 

 live tree roots, the moisture fell to or below the wilting coefficient 

 in four instances during the season at the 6-inch depth, and in 

 three instances at the 12-inch depth, whereas in the area occupied 

 by no live tree roots the lowest point reached even at 6 inches was 

 0.4 per cent above the wilting point. 



