The true desert of the Central-West Argentina bioclimatology, geomorphology and vegetation

in the nw sector of argentina between the latitudes of mendoza (32°53’s) and jachal (san juan) (30°15’ s) extends a ns oriented tectonic valley located between the pre-cordillera and the front cordillera of the andes. this valley is 2,000-5,000 m deep with respect to the pre-cordillera and cordillera summits that borders it on the east and west; it is ca. 300 km long and 40 km wide on the average. this is actually a perfect case of rain shadow desert comparable to the well known californian death valley, with an hyperarid climate. at the lowest point (calingasta -san juan-, 1,375 m) the long-term mean annual rainfall is only 54 mm and up to 100-120 mm on the highest points (tambillos -mendoza-, 2,164 m). from the geomorphic, climatic, floristic and vegetational viewpoints this posttectonic graben is a true desert void of perennial vegetation on the pediments, while perennial species are contracted along the hydraulic network and around the topographic depressions. vegetation on the pediments is set up in a steppe-like diffuse pattern in the highest parts above 1,800 m of elevation, and on a contracted pattern in the lower (1,300-1,800 m asl).