Vegetation in an altitudinal gradient along the Río Loa in the Atacama Desert of northern Chile

Six sites between 0 m and 4000 m were sampled for plant and soil chemical characteristics along the Río Loa, Atacama Desert, Chile. Sites located between 0 m and 1500 m showed lower species richness, higher plant cover and higher herbaceous productivity than the upper part of the altitudinal gradient. The number of species varied non-linerly with precipitation along the altitudinal gradient. Plant cover and herbaceous productivity in the lowlands is characterized by thePluchea absinthioides Distichlis spicataassociation of anthropic origin. We propose that vegetation structure along the altitudinal gradient has been affected by past and present human activities, and climatic and edaphic factors