50 THE BROAD-SCLEROPHYLL VEGETATION OF CALIFORNIA. 



season following. The two graphs side by side (figs. 9 and 10) give 

 the minima shown in table 6. This shows that there are very 

 perceptible differences in water-content at the critical periods 



Table 6. 



following winters of deficient and abundant rainfall, and that these 

 differences appear especially in the deeper soil-layers. In the 

 chaparral, at 100 cm. depth, the minimum percentage after a wet 

 winter was more than three times that of the preceding season; 

 at the corresponding forest depth the percentage was more than 

 twice that of 1913. 



Series II. 



This series was carried out at the same six stations that were 

 used for the evaporation studies, and during the same period (June 

 15, 1913, to April 17, 1914). There were thus provided three 

 examples of Adenostoma chaparral (Nos. 2, 4 and 10), two of 

 Arctostaphylos chaparral (Nos. 3 and 6), and one of forest (No. 7). 

 The samples were taken at intervals of 4 weeks, and in stations 2, 

 3, 4, and 6 at two depths — 10 cm. and 30 cm. In stations 7 and 

 10 the figures from Series I were used, the 50-cm. depth being con- 

 sidered as parallel to the 30-cm. depth in the other stations. In 

 figure 11 the results for the 10-cm. depth are compared. 



The most striking feature is the line representing station 2, the 

 highest in water-content and yet the poorest in vegetation. The 

 explanation of this apparent paradox is found in the mechanical 

 analysis and wilting coefficient. The sudden changes in water- 

 content without apparent reason — e. g., the sharp crest on July 13 

 and the sudden drop after March 4 — are perhaps due to local soil 

 differences, small masses of unusually high or unusually low clay- 

 content. The other two Adenostoma stations are consistently the 

 lowest and the forest is the highest. Between forest and Adenos- 

 toma chaparral are the two Arctostaphylos stations. In figure 12 all 

 stations of each type, both depths, have been averaged, station 2 

 being omitted. The daily precipitation for the period is also added. 

 The Adenostoma community is decidedly the lowest, and the forest 

 is highest most of the time, though the Arctostaphylos community is 

 not far below. The close approach of all the lines during the dry 

 season and their separation during the wet season (seen in Series I) are 



