Heterogeneidad de la vegetación en ambientes basálticos del centro de Argentina.

Heterogenity of the vegetation of basaltic environments in central Argentina. The flora and the vegetation of basaltic outcrops of Los Condores Mountains, central Argentina, are described. Plant communities were sampled following the Braun-Blanquet methods. The 98 releves × 272 species matrix was classified through the ISOPAM method. The classification discriminated three main communities occurring in the three different substrates explored in this landscape: Rocky Islands (inselbergs), a Natural Matrix surrounding the Islands and an Agricultural Matrix, surrounding the whole basaltic area. The three communities differed in composition and physiognomy: the Islands were the less disturbed sites, reporting the highest plant species richness and diversity as well as the higher number of endemics, and the lowest number of exotic species. In the other extreme of the disturbance gradient, the Agricultural Matrix showed the opposite patterns and is dominated by annual and perennial herbs, mainly weeds. While the number of aliens is low in the Islands and in the Natural Matrix, almost 50% of the species are exotic in the Agricultural Matrix. The results of this study reveal that the basaltic inselbergs are relevant sites for the conservation of the natural heritage.