NOTES ON DUNE VEGETATION AT SAN FRANCISCO, 



CALIFORNIA ,q^, 



FRANCIS RAMALEY Vw \ ' ^^^'^ ^jf" 



University of Colorado, Boulder, Colorado X^V / *V> 



The dunes^ here considered extend south from Golden GateX^J^ ^^ jb3^ 

 Park^ about 5 km. and inward from the ocean 2 to 4 km. An 

 automobile highway parallels the ocean shore at the west but 

 has had no influence upon the dunes or their vegetation. Pre- 

 vailing winds are west-south-west; winds from other directions 

 seem to be of no consequence. 



Conditions for plant life at San Francisco are severe. As is 

 well known, the climate exhibits a rainy and a dry season, the 

 rains being confined to winter and early spring. The rest of 

 the year is without precipitation. Soils dry out, and only 

 xerophytic plants are to be found most of the year except in 

 ravines, on north slopes or in other favored places. The plants 

 of dunes and sand hills are, of course, subject to this unfavorable 

 climate, also to austere soil conditions. The sand of the dunes 

 is light and even in very moderate winds is continually being 

 blown along and can be seen rising 1 to 2 dm. at almost any 

 time.^ 



The severity of conditions is shown by the large areas, often 

 500 meters square, with no vegetation whatever. Then there 

 are still more extensive tracts with only occasional mounds 



1 The writer became acquainted with these dunes while giving courses in the 

 summer session of the University of California, June-August, 1917. At the close 

 of the session a number of days were spent at San Francisco in continuous field 

 study. 



2 Visitors to San Francisco can reach the dunes by street car, taking line 

 7, 12 or 17 from the Ferry Building at the foot of Market Street, riding to near 

 the end of the line. 



2 A chemical analysis of the dune sand at San Francisco is given by Olsson- 

 Seffer in his article on Relation of soil and vegetation on sandy sea shores, Bot. 

 Gaz. 47: 85-126. 1909. 



191 



THE PLANT WORLD, VOL. 21, NO. 8 

 AUGUST, 1918 



