Altitudinal gradient of plant diversity patterns in the Sierra de Quilmes (Monte desert – Argentina)

Abstract

The Monte Desert is the most arid rangeland in Argentina. Its northern portion, the High Monte ecoregion, is a geomorphologically complex area, characterized by mountain and bolsons landforms. Yet, most studies about plant diversity in the area have disregarded the altitudinal gradient. We examined the patterns of species richness, composition, and diversity along an altitudinal gradient in the Sierra de Quilmes (High Monte ecoregion), through the deconstruction of biodiversity into growth forms. We sampled vegetation from eight sampling sites in each of five altitudinal bands ranging from 1650 to 2550 m a.s.l. We found 123 species belonging to 33 families. Community composition changed with altitude. The abundance of shrubs increased with altitude, while the abundance of trees decreased. Both alpha and beta diversities peaked in the lowest and intermediate altitudes (1700 and 2300 bands). This pattern was particularly consistent for woody plants. The higher beta diversity in the 1700 band might result from geomorphology and soil features variation. The remaining gradient conformed to a hump-shaped pattern with a peak in the 2300 band, which may present more suitable climatic conditions. This study contributes to a broader understanding of the causes determining vegetation diversity patterns in the High Monte Desert.