ISSN 373 • 580 X Bol. Soc. Argent. Bot. 34 (3-4): 127-148. 2000
VEGE TACI ÓN DE LOS AND ES CENTRALES DE LA ARGE NTIN A. EL VALLE DE USPALLATA, MEN DOZA EDUAR DO MARTIN EZ CARRE TERO"
Summa ry High Central Andean Vegetation of Argentina. Uspallata Valley, Mendoza. In the trame of the central Andean vegetatlon of Argentina, the vegetat ionof Uspalla ta was phytosociologically and chorologically analysed. The Uspallata valley is of tectonic origin and is limitad by the Frontal Cordillera in the West and the Precordillera in the East. The most arid sector ls the valley itself with an annual rainfall of 100 mm, which increases towards the East and mainly towards the West In the high crests. However, the valley is the only cultivated sector beca use of the great availability of water for irrigation, mainly supplied by the Uspalla ta and San Alberto streams. The presenc e of xerophytic thickets was determi nad in the valley (Larrea cuneifolía Cav.) and in the higher parts of the mounta in sector (Adesm ia horrida Hook. et Am.). The latter is xerophytic due to freezing of soil water. The mesoph ytlc thicket of Artemisla mendozana DC is located between both vegetation levels. Communities of Dolichlasium lagasca e Gill. ex Don and Guindilia díssecta (Cov. et Burk.)Hunz. appear in the fissures of rocky outcrops there which correspond to the sunny and shady spots respectively. Rlparian vegetation, principa l! y bushes of Proustia cuneífolia D.Don fa. mendocina (Phii.)Ariza and forests of Discaria trinervis (H. et A.)Reiche are found along streams, which are either perman ent or temporary. Associated with these streams are swamp y commu nlties, xerophytes with Cortaderia rudiuscula Stapf. enmend. Aceved o, hygroph ytes with Juncus balticus Willd. and hydroph ytes with Rorippa nasturtiumaquatic um(L.)H ayek. The chorological types usad follow Cabrera (1976). In each community the presenc e and cover percentages of each chorologlcal type were calculated, drawing the respect ive spectra; interesting relalion s betwee n chorolo gy and cover were found in them. For example in the dry commu nity of"Stipa chrysophylla var. crispula Parodi the Puna elemen ts domina te, while dueto its cover this grassla nd corresponds to the high Andean phytogeographic province ; and in the Cortaderia rudiuscula community which shows majority of Monte species but Patagonian physiog nomy. The analysis was completad with the vegetation map of the area.
Key words: Community, chorology, vegetation map.
INTRO DUCCI ÓN
El estudio fitosociológico del valle de Uspallata,. con su corresp ondien te carta de vegetación, forma parte de uno mas amplio: estudia r la vegetación de los altos Andes Centrales de la Argentina. Ademá s, constituye parte de la información básica para el ordena miento territorial de este import ante valle altoand ino. El area estudia da abarca una superfi cie de 128,30 km2• Desde el clásico trabajo de Haum an (1918), el posterior de Bocher, Hjerting & Rahn (1963 y 1968) para· el valle del Atuel en el sur de Mendo za, el esquem ¡;¡ de la vegetación del Paso de Uspallata de Ambrosetti, Del Vito & Roig (1986) y el de Roig & Martín ez Carrete ro {1998) para la Puna austral , no • se intenta ron nue_vos trabajo s perman eciend o aún • UID Botánica y Fitosociologla, IADIZA ,CC 507,5500 • Mendoza Trabajo financiad o con fondos de CONICET, PIP 4680/96
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sin estudi ar grande s extens iones del territo rio andino . . El valle de Uspallata es un área interesante des· de el punto de vista fitogeográfíco y corológico, pudien do pasarse, en sentido E-W, de un ambien te de Puna (much as de cuyas especies encuen tran aquí su límite austral) a otro del Monte y finalmente al Altoandino. Posee ademá s numer osos endernismos.
Clima El valle posee un clima local muy árido con mayores temper aturas y menore s precipitaciones, casi la mitad, que otras localid ades cordilleranas próximas como Puente del Inca (2700 m s.m.) y Cristo Redentor (4200 m s.m.). La aridez se acentúa hacia el norte que constit uye la zona mas xérica con preci· pitaciones menore s a 100 mm anuales. La influencia de los dos cordon es montañosos: Precordillera (al este) y Cordillera Fronta l (al oes·