Trees (2005) 19: 661–670 DOI 10.1007/s00468-005-0430-7 ORIGINAL ARTICLE F. Abdoun · A. J. T. Jull · F. Guibal · M. Thinon Radial growth of the Sahara’s oldest trees : Cupressus dupreziana A. Camus Received: 15 April 2004 / Accepted: 7 April 2005 / Published online: 27 April 2005 C  Springer-Verlag 2005 Abstract The radial growth of Duprez’ cypress (Cupres- sus dupreziana A. Camus), a tree endemic to the Tassili n’Ajjer in the Central Sahara, was measured from cores taken in 1967 and 1997 from the same trees. A compari- son of these cores, spanning 30 years, reveals that even in this hyper-arid climate, this species has a juvenile vigour comparable to other Mediterranean Cupressaceae. Wide individual variability was found, however, which was in- duced by the strong influence of microhabitat factors. Tra- ditional dendrochronological methods of cross-dating are impossible to apply in the case of these trees. Ages of eight individuals were estimated with the help of radiocarbon dating, yielding an age range from 600 to 2400 years for trees of the most usual girths. Keywords Cupressus dupreziana, Radial growth . Tree ages . Tassili n’Ajjer . Sahara This work is dedicated to the memory of Franc ¸oise Serre. F. Abdoun () UMR EcoBio 6553, Universit´ e Rennes-1, Bˆ at 14-A Campus Beaulieu, 35042 Rennes Cedex, France e-mail: fatabdoun@yahoo.fr Tel.: 33-(0)-2-35-14-66-56 Fax: 33-(0)-2-35-14-66-55 A. J. T. Jull NSF Arizona AMS Laboratory, The University of Arizona, Physics Building, 1118 East Fourth, St. Tucson, AZ 85721, USA F. Guibal Institut M´ editerran´ een d’Ecologie et de Pal´ eo´ ecologie, CNRS UMR 6116, Europ ˆ ole M´ editerran´ een de l’Arbois, Pavillon Villemin, BP, 8013545 Aix-en-Provence Cedex 04, France F. Abdoun · M. Thinon Institut M´ editerran´ een d’Ecologie et de Pal´ eo´ ecologie, CNRS UMR 6116, case 462, 13397 Marseille cedex 20, France Introduction The very presence of Duprez’ cypress (Cupressus dupreziana A. Camus) in the hyper-arid climate of the Central Sahara constitutes a considerable botanic curios- ity. First encountered by scientists in 1924 (Maire 1933), the species only exists in the wild in the Tassili n’Ajjer in south-eastern Algeria. Initial observations made in the 1920s led to the view that the handful of elderly trees found were the remains of a forest that had grown in an earlier, wetter climate (Lavauden 1926). Based on this view, one would conclude today’s infrequent and irregular rainfall should not allow these seedlings to develop. Some authors (Lavauden 1926; Barry et al. 1970) considered that the sur- vival of these trees was due to a powerful root system draw- ing water from underground aquifers. It also appeared that these trees would eventually die of old age without repro- ducing and germinations would not survive the drought, whereupon the species would inevitably become extinct (Barry et al. 1970). Duprez’ cypress was accordingly clas- sified by the IUCN (International Union for Conservation of Nature) as among the 12 most endangered species in the world (Lucas and Synge 1978). Of the first trees observed, ten of them have impressive trunks of up to 12 m in girth, giving credibility to the hy- pothesis of a “forest relic” condemned to disappear by the drying of the climate (Barry et al. 1970; Lucas and Synge 1978; Stewart 1969). For these trees, ages of many thou- sands of years had been proposed, which would go back to times when the area was occupied by Bovidian pas- toralists who painted many of the famous cave frescoes nearby (Lhote 1958). Knapp (1973) suggested an age of 4700 years, referring to Meyer (1961/1962) and his sum- mary paper on the world’s oldest trees. The latter author in turn refers to Simonneau and Debazac (1961) who use Qu´ ezel’s scenario in which the Sahara started drying out around 2800 bc (Qu´ ezel 1960). That date matches the age of ancient organic traces (Rock Hyrax droppings) contain- ing a rich pollen load and radiocarbon-dated to 4680±300 years bp (Pons and Qu´ ezel 1958). As early as the 1950s,