72 CARNEGIE INSTITUTION OF WASHINGTON. 



soils. Recently the importance of this factor in the distribution of 

 vegetation, or in any ecological work, has been emphasized, so that 

 measurements of the hydrogen-ion concentration of soils, particularly 

 during the growing season, may be regarded as requiring consideration 

 along with the measurement of any climatic or other soil factor. 



Ordinarily, in humid regions one thinks of bog, peat, or muck soils as 

 acid, and often strongly acid, while most agricultural soils are less acid, 

 varj'ing not infrequently from pH 4.5 to pH 7.0, with the majority 

 from pH 5.0 to 6.0. On the other hand, the indications are that soils 

 of arid regions are more frequently alkaline. Employing the suspen- 

 sion method and using the standard solutions and indicators of Clark 

 and Lubs, I have examined about 35 samples of soil from the Carmel 

 Valley or adjacent hills and a smaller number of samples from the 

 Salinas and Pajaro Valleys. Unless otherwise indicated, these samples 

 were taken from 1 to 4 inches below the surface. In all cases where 

 clear solutions were unobtainable the determinations were made with the 

 aid of the microcolorimeter of Duboscq. The samples from the Carmel 

 Valley represent practically all procurable soil types and vegetation 

 areas, including hillsides, stony terraces, or bench lands (both pasture 

 and cultivated), rich alluvial deposits, and flats, fixed dunes near the 

 beach, and several types of bogs. 



The outstanding feature of interest is the relatively narrow range of 

 reaction, pH 6.2 to pH 7.4. The more alkaline types were those of 

 the lower flood-plain of the river or river-bottom, often pH 7.2, and 

 certain adobe soils taken at a depth of a foot or more below the sur- 

 face. The two bogs examined gave values respectively 6.2 and 6.6, 

 the former from a rush-scirpus association and the latter from a willow- 

 agrimony association. All soils from cliaparral areas, terraces, and hill 

 pastures were within the range pH 6.2 to 6.6. All determinations were 

 made during July and August. 



A Soil-Temperature Survey of the United States and Canada, by Forrest Shreve. 



The reappointment of the committee on Soil Temperature of the Eco- 

 logical Society of America, consisting of Forrest Shreve and Dr. Alfred 

 E. Cameron, has given opportunity for the continuation of this project. 

 The progress of the work is due to the faithful and interested coopera- 

 tion of the men who are conducting the observations and operating ther- 

 mographs at the scattered stations in the United States and southern 

 Canada. The movement of observers to other fields of work has 

 necessitated the discontinuance of 7 of the original series of 29 stations; 

 6 new stations have been secured in new localities, some of which fill 

 large gaps in the distribution of the series. At 4 of the stations read- 

 ings are being taken at more than one depth or in more than one tjT^e 

 of soil. It has happened in several cases that observers were not able 

 to continue their readings tlu'ough the winter months, and in a few 



