Contribución al estudio de la vegetación y su relación con la geodiversidad en ambientes serranos de Sierra de los Padres y Sierra La Brava, en el extremo sudeste del Sistema de Tandilia (Buenos Aires, Argentina)

Background and aims: The Tandilia rangelands represent sites of high bio and geodiversity, however, plant communities are threathened by invasion of exotic species. This study aims to characterize and compare the floristic composition and richness of the different geoforms on northeastern and southwestern slopes in two hills in the districts of General Pueyrredon and Balcarce, with different degrees of invasion of Acacia melanoxylon. M&M: A stratified sampling by geoform was carried out, on both slopes, in a hill with low (in Balcarce) and high (in General Pueyrredon) percentage of invasion of A. melanoxylon, where richness and coverage of vascular plants was measured. A phytosociological analysis, a correspondence analysis and a comparison of richness by geoform and slope were carried out. Results: We identified 187 species whom 80,75 % were native to Pampa ecorregion. Poaceae and Asteraceae were the more diverse recorded families. Floristic composition partially vary with different geoform and A. melanoxylon invasión. The Upland, Slopes and Colluvial deposits present the richest communities. No differences were observed between northeast and southwest slopes. Conclusions: The floristic characterization and richness patterns reported, provide valuable information on the influence of geomorphological variability and the presence of invasive species in the two mountain ranges of southeastern Tandilia for consideration in the conservation of the mountain biota.