NO. 



DUNKLE : PLANT ECOLOGY, CHANNEL ISLANDS 283 



well justify the term of sea bluff formation. There are frequently three 

 distinct zones of the sea bluff; (1) the break of the bluff, (2) the 

 talus slope, and (3) the splash zone. 



Breaks. The break of the bluff is the place where the normal slope 

 of the hinterland changes angle and where both wind and water erosion 

 become abruptly more effective. The width of this zone may vary from 

 a few feet, at the edge of a perpendicular cliff, to several hundred feet 

 at the upper part of a more gradual slope. The zone has a fairly coarse, 

 residual soil which rapidly becomes more shallow as the slope increases. 

 The angle of the break is frequently accentuated by an outcropping of 

 rock — the rim-rock — which forms a broken row of cliffs. This may, 

 where the wave action is especially powerful, extend to the water's edge. 



The communities of the breaks show considerable variation due to 

 the slope exposure and the exposure to wind. On the higher, wind- 

 swept breaks there is little rim-rock. Astragalus Traskiae and a low 

 form of Hemizonia clementina are the principal suffrutescents. The 

 annuals include Baeria hirsutula and Malacothrix foliosa. 



The still higher breaks of the south peak are not nearly so windy as 

 the breaks of the north peak. In addition to the plants of the north 

 peak may be added A triplex calif ornica, Mesembryanthemum crys- 

 tallinum, Amblyopappus pusillus, and Lotus argophyllus ornithopus. 



The lower southern breaks are still more protected from the pre- 

 vailing wind and included the following additional plants: Mirabilis 

 laevis, Opuntia prolijera, Cryptantha Traskae, and Muhlenbergia 

 microsperma. These, with the others listed from the southern canyon 

 slopes form an open association which varies from place to place with 

 no distinct dominants. The coves of the southern breaks may be desig- 

 nated as an Opuntia-Lotus association. 



Precipitous cliffs completely rim the western section of the island 

 so that the cliff breaks there are extremely narrow. This is a bleak 

 region with strong winds, fogs, and hundreds of nesting gulls, pelicans, 

 and cormorants. Atriplex californica, Mesembryanthemum crystallinwn, 

 foliose lichens, and an occasional ruderal, such as Sonchus or Malva, 

 form a scanty and drab open community. There is a single plant of 

 Lotus growing in a shallow niche at the extreme western tip of the 

 island which gives the only spot of color that is to be found along these 

 western breaks. An occasional low, prostrate plant of Hemizonia 

 Clementina will be found in crevices along the edge of the cliffs. This 

 is the same low form of Hemizonia with very short internodes and 

 procumbent habit which marks the Hemizonia plants found in windy 



