FOREST DISTRIBUTION IN THE SAN JUAN ISLANDS: 

 A PRELIMINARY NOTE» 



GEORGE B. RIGG 

 University of Washington, Seattle, Wash. 



The San Juan Islands are a part of the state of Washington 

 and are situated between the Strait, of Juan de Fuca and the 

 Strait of Georgia. There are on these islands four conspicuous 

 cases of hills in which the north slope is densely forested while 

 the southern slope is practically destitute of trees. The forest is 

 largely coniferous and is mainly of one species — Pseudotsuga 

 taxifolia. The four elevations referred to are: (1) the hill at 

 Cattle Point at the southern end of San Juan Island; (2) South 

 Hill, near the town of Friday Harbor, on the same island; (3) 

 Spieden Island, which is a narrow island about two miles long, 

 extending in an east and west direction just north of the northern 

 end of San Juan Island, and (4) Sentinel Island, which is small 

 and rounded, and is situated just south of Spieden Island. 



Of these four hills the one at Cattle Point is the most conspicu- 

 ous because it is situated near the path of commerce and is so 

 located that the contrast between the two slopes can be readily 

 seen from passing ships. The distribution of the forest at that 

 point is frequently commented on and the question as to its cause 

 raised. The trees at the summit of Cattle Point Hill show the 

 effect of the strong southerly winds which prevail there, especiall}^ 

 during the winter. Many of the trees on the ridge of the hill have 

 their branches much better developed on the north side than on 

 the south. In some cases branches originating on the south side 

 of a trunk have their direction entirely reversed and grow toward 

 the north. In other cases even the whole tree is so bent toward the 

 north as to be almost prostrate, the trees thus affected being mainly 

 Pseudotsuga taxifolia and Pinus contorta. In many of the trees 



' Contributions from the Puget Sound Marine Station Xo. 3. 



177 



