EESEAECH METHODS IX STUDY OF FOREST ENVIRONMENT. 



69 



standard temperature of — 4° C, and when the process was repeated 

 on the same sample several times. Without going further into these 

 details. Avhich are readily available in the original article, one more 

 fact should be mentioned, namely, that the moisture contents at which 

 various soils fail to show definite freezing points, and similarly the 

 contents which by the method just described are found definitely not 

 to freeze, bear a close relation to the wilting coefficients of the same 

 soils. 



Directly bearing on the point as to the part played by the colloidal 

 masses of the soil. Bates (105) found, for eight samples of Michigan 

 and Nebraska sand, each taken at a depth of 1 foot, and consequently 

 showing a maximum of 2 per cent humus, that there was a linear re- 











DIAGRAM 1 

































RELATION OF WILTING COEFFICIENTS 



TO 



SILT AND CLAY CONTENTS 



OF 

 MICHIGAN SANDS 



3 ol-foot samples containing little humus, 

 x Surface samples with more or less humus 



























































































(A 













































UJ <T3 













































-fa 

 £.2 





















































































































X 





















X 





















































__2 

























^£ 











x^_ 













X 































"""unf 

















































































_ i 





_£j 







5 



LT , 



<\nd 



CLA 

 5 



K" C( 



NT^ 



NT, 



Perc 



snta 



e 





3 













lation between the final wilting coefficients for jack and Norway pines 

 OH the one hand, and the combined silt and clay contents of the re- 

 -pective soils on the other. The latter varied from 0.3 to 6.4 per 

 cent. The behavior of surface soils with larger humus contents was 

 different; but these, when decidedly lucking in humus, might give 

 even lower values than the deep soils, probably on account of more 

 thorough leaching. The results, as shown in diagram 1, indicate that 

 if -ilt Mini flay \\<tc entirely eliminated, the sands might still possess 

 a wilting coefficient of about 0.43 per rent. This is extremely dose 

 to the \:ilne for unfree water which Bouyoucos round to be almost 

 constant in the case of quartz sand, regardless of the experimental 

 condit ions. 



The conclusion is t here tore reached that, in the final st niggle which 

 determines whether the plant shall obtain sufficient water for its 



