10 



THE VEGETATION OF SHACKLEFORD BANK 



PHYSIOGRAPHY 



The eleA'ation of Sliackleford A'aries from sea-level in the marshes to 

 20-25 feet in the higher ground of the interior. Toward Cape Lookout 

 Light are some shifting dunes perhaps 35 or 40 feet high. 



The physiographic conditions on Shackleford are causing rapid 

 changes in the vegetation of the Bank, which will be referred to later. 

 At present it is sufficient to state that the sand of the beach is advancing 

 on the forest at a comparatively rapid rate, destroying the vegetation 

 in its path. 



CLIMATE 



The climate of Shackleford is very similar to that of Hatteras, de- 

 scribed by Kearney.i From data furnished by the United States 

 Weather Bureau for Beaufort (2 miles from Shackleford) and Hatteras, 

 the following points of difference are taken : 



The annual mean temperature of Beaufort for the last six years is 

 63.6° F. (17.5° C), while that for Hatteras for the same period is 62.3° 

 F. (16.8° C). The maximum summer temperature of Beaufort is 

 slightly higher (about 3° F.) than that of Hatteras, while the minimum 

 winter temperature is slightly lower. There are practically no days at 

 either place when the temperature does not rise as high as 43° F. (6° C). 



The latest killing frost in spring, and the earliest in autumn, occur 

 at about the same time in both places (February 25 and December 13). 



The amount of sunshine during the year is less at Beaufort than at 

 Hatteras. At Beaufort the average number of rainy days during the 

 year is 128, clear days 117, as against 118 and 204 for Hatteras. The 

 intensity of light is greatly increased at both places by reflection from 

 the water and the white sand, so that the actual amount of light avail- 

 able for the use of plants is greater than at an inland station with the 

 same number of sunshiny days. 



No data are available for determining the atmospheric humidity. The 

 prevailing wind during the growing season is from the southwest, and 

 is laden with moisture from the Gulf Stream, so that the average hu- 

 midity is probably not less than at Hatteras, where it is notably high. 



The annual rainfall is even greater at Beaufort than at Hatteras. 

 During the years 1896-97-98 and 1906-07-08 (the only years for which 

 data on this point are available for both stations) the average annual 

 precipitation at Beaufort was 58.59 inches, at Hatteras 53.12 inches. 

 However, the estimated mean annual precipitation is greater for Hat- 



^Kearney: The Plant Covering of Ocracoke Island; Contributions from the U. S. Nat. Herb.> 

 Vol. 5, No. 5. 1900. 



