The Brahea edulis palm forest in Guadalupe Island: a north american fog oasis?

Abstract

Fog is a factor that affects deeply the structure of vegetation of coastal deserts. Guadalupe is an oceanic island located 260 km off the coast of Baja California, and is one of the few places of the Sonoran Desert coasts with scarped coastal topography and frequent fog. With the aim to identify the effect of fog on the community of the palm forest (palmar) of Brahea edulis located in the northern tip of the island: (1) we analyzed the richness and composition of vascular plants in the palmar compared to the remainder of the island, and (2) we analyzed the altitudinal variation of the abundance of palms, herbs and mosses to identify if there is altitudinal variation of the vegetation. Although species composition was not different between palmar and the rest of island, species richness and vascular plant cover were greater in the palmar. On the other hand, we found a clear altitudinal zonation of the vegetation in the palmar that is similar to that found in South American fog-driven plant communities such as the lomas. Thus, the palmar community of Guadalupe Island may be considered as a fog oasis, one of the very few that occur in North America.