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Community Structure and Diversity in a Coastal Fog Desert in Northern Chile

1976; Elsevier BV; Volume: 165; Issue: 6 Linguagem: Inglês

10.1016/s0367-2530(17)31888-1

1618-0585

Philip W. Rundel, Manuel Mahú,

Marine and coastal plant biology

Coastal fog deserts along the coast of Northern Chile provide unusual opportunities to study mechanisms controlling structure and diversity of desert plant communities. At Paposo, Antofagasta Province, regular coastal fogs known as the Camanchaca hang against the steep coastal topography in a zone between 280 and 830 m. Despite a mean annual precipitation of less than 25 mm, fog drip provides sufficient moisture for the development of a luxuriant fertile zone. Below the fog zone vegetation is sparse, while above it vascular plant life is virtually absent. In the central fog zone vegetation coverage may reach 50 %. Individual growth forms of vascular plants sort out well along an elevational gradient through the fog zone. Woody deciduous species reach their greatest coverage within the central fog zone, while deciduous subshrubs reach maximum coverage at the margins of the fog zone. Succulents likewise have maximum coverages above and below the fog zone. Data on competitive relationships between Euphorbia lactiflua, a woody deciduous shrub, and Eulychnia iquiquensis, an arborescent cactus, indicate that high densities of Euphorbia in the central zone have little impact on densities of Eulychnia, but do reduce coverage values of this latter species. Species diversity of communities along an elevational gradient are not related to coverage values but are directly related to grow-form diversity, thus indicating intergrowth-form competition is greater than intra. growth-form.