Abstract

Isla de los Estados (Argentina) is located in the South Atlantic Ocean and formally is a natural reserve of Tierra del Fuego province due to its particular marine fauna. However the different terrestrial ecosystems, including mountain areas, suggest the potential of unique biodiversity assemblage without significant human impacts. The objective was to analyse the differences in plant and bird richness and abundance (cover/density) comparing lower and upper altitude environments in forests (mixed evergreen dominated by Nothofagus betuloides) and open‐lands across the landscape (2 ecosystem types x 2 altitudes in 3 fjords along E‐W gradient). A total of 35 plant species was detected, which decreased in closed forest and increased in open‐lands with altitude (16 to 20 species, and 26 to 20 species, respectively), where differences in richness and cover where detected between environments and fjords. Beside this, a total of 33 bird species was detected, with a decreasing of richness in forests and open‐lands with altitude (12 to 8 species and 13 to 11 species), where differences in richness and density where detected between environments and fjords. Plant species assemblage was influenced by environment type and altitude, where some species presented clear preferences for alpine environments (e.g. Bolax gummifera, Escallonia serrata, Maytenus disticha, Azorella lycopodioides and Festuca contracta). In the case of bird species, the assemblage was more influenced by environment type than altitude, however some species presented greater preference for alpine environments (e.g. Vultur gryphus and Polyborus australis). Results suggest that mountain environments present a similar conservation value than lower altitude environments, where open‐lands maintained more species and abundance than forests.