Journal of Arid Environments (1999) 42: 305–317 Article No. jare.1999.0517 Available online at http://www.idealibrary.com on Saxicolous and riparian vegetation of a piedmont in central-western Argentina E. Martinez Carretero* Botany and Plant Sociology, Argentine Institute of Arid Lands Researches (IADIZA), CC 507, 5500 Mendoza, Argentina (Received 31 July 1998, accepted 24 March 1999) Four plant communities were determined through floristical and non-metric analysis: a Dolichlasium lagascae community in crevices on sunny rock out- crops; a Cercidium praecox ssp. glaucum community on sunny slopes; an Artemisia mendozana}Adesmia trijuga community on shady slopes; and a Eupatorium buniifolium community on dry riverbanks. T he discriminant func- tion analysis showed that the first group corresponds to the sunny rock outcrops discriminated by Na content ( r"0·53, p(0·05), the second group is for sunny slopes discriminated by electric conductivity and the third for shady slopes}riparian discriminated by the (Ca#Mg) content ( r"0·54, p(0·05). A pattern of primary succession on outcrop surfaces is proposed.  1999 Academic Press Keywords: arid; outcrop; saxicolous vegetation; xerosere Introduction An outstanding feature of saxicolous vegetation is its occurrence in environments where microtopography plays a major role. There is much information concerning the com- position and succession of outcrop plant communities, though most of it deals with granite outcrops (Baker, 1956; Burbank & Platt, 1964; Shure & Ragsdale, 1977; Funes & Cabido, 1995; Wiser et al., 1996). Only a few ecological and floristic studies on saxicolous vegetation have been made in Argentina, generally because of their limited extent and frequent inaccessibility. Frangi (1975) described saxicolous vegetation for the Sierra de T andil, Cabido et al. (1990) for granite outcrops of the Sierras de Co H rdoba and Funes & Cabido (1995) analysed local and regional variability in the saxicolous vegetation of the Sierras Grandes in Co H rdoba Province. Roig (1976, 1989) studied the plant communities of the piedmont in the Province of Mendoza, and described saxicolous communities present on shady ( Adesmia trijuga community) and sunny slopes ( Astericium glaucum Hieron. et Wolff community). Martinez Carretero (1985, 1987) and Martinez Carretero & Roig (1994) studied the ecological aspects of these communities, particularly those related to water erosion and soil characteristics. Associated with the Andean tectonics that began during the Upper Tertiary and continued until the Lower Quaternary, the rock outcrops of the Andean piedmont are primarily composed of consolidated Triassic sandstone (Barton & Rodriguez, 1989) *(E-mail: mcarrete@lab.cricyt.edu.ar). 0140-1963/99/080305#13 $30.00/0  1999 Academic Press