Cupressus dupreziana (Tarout) description

Cupressus dupreziana

A. Camus 1926

Common names

The Algerian variety described here is called Saharan cypress [English], سرو صحراوي [Arabic], Tarout [Tamashek]. "Tarout" was originally a butcher’s term for the windpipe and attached lungs of a grazing animal, to which the tree bears a fancied resemblance. Since there are so few of them, in the local language [Tamashek] they are also named individually, e.g. “The One by the Flat Stones” (Werner and Bubriski 2007).

Taxonomic notes

During the Pleistocene glaciations, the Mediterranean coast of north Africa seems to have had a fairly continuous forest. Subsequent desertification (both climatic and anthropogenic) has reduced this forest to isolated pockets, that now host similarly isolated taxa of conifers; in this case, three taxa of Cupressus (assessment based on Dallimore et al. 1967 and Farjon 2005). In Libya there are two coastal areas assigned to C. sempervirens, a taxon most widely distributed in the northeast Mediterranean. In Algeria there is a tiny inland population, deep in the Sahara, assigned to C. dupreziana var. dupreziana, described on this page; and in Morocco there is an interior population assigned to C. dupreziana var. atlantica, which has also been described as a distinct species, here treated as C. atlantica; see that page for its description.

Synonyms include Cupressus lereddii Gaussen 1950, and C. sempervirens var. dupreziana (A. Camus) Silba 1981 (Farjon 1998). The species was described "based on fragmentary material collected by M. Lavauden during his journey over the Tassile range in the Sahara between Rhat and Djanet early in 1925" (Dallimore et al. 1967).

Description

Tree to 20 m tall (the tallest measured, 20 m, has lost its top) and 3 m dbh. Young specimens grown in protected conditions are first bushy, later developing a straight central axis. Bark is reddish-brown, with deep longitudinal fissures, lacking decortication. Branches diverge from the trunk at large angles, curving upwards. Ramification of first and second order shoots tends to be strong in 2 planes; first-order shoots are flattened. Leaves are cupressoid scales, opposite, decussate, imbricate, slightly appressed, acuminate, 1-1.5 mm long, dull green, slightly glaucous; resin gland elongated, not noticeable except on the base of old leaves. Foliage very dense. Seedlings have with 2 cotyledons and glaucous, aciculate leaves 2-3 mm long. Plants monoecious. Pollen cones terminal, yellow, elongate, 6×3 mm. Female cones terminal, purple, ovoid, c. 2.5 mm diameter, developing into and elongated cone 18-24×16-20 mm; grey-brown, matte, with 12-19 scales having a very small, rounded mucro. Seeds reddish-brown, oval, flattened, 4-5×5-6 mm, with wide, thin wings. Pollen spherical, 38 microns diameter (FAO 1986).

Distribution and Ecology

Algeria: Confined to an area approximately 100 km long by 40 km wide, along the southwestern border of the Edeni (or Tamrit) plateau of the Tassili N'Ajjer massif in the central Sahara, around 9°E 25°N, at 1000-1800 m elevation. The summer temperatures are estimated to be ca. 20-30°C, in winter ca. 1-13°C. Frosts of -7°C likely occur. Annual rainfall is ca. 30 mm, highly variable. The trees grow in wadis on alluvial gravels and sands (FAO 1986).

Data from Ramdani et al. (2007).

There are 233 living specimens and many more snags (Abdoun and Beddiaf 2002). Only two cases of naturally occuring seedlings have ever been recorded, and there are no trees younger that at least a century (only 5 trees have been recorded with a dbh 50 cm or less, the smallest being 13 cm) (FAO 1986). It is believed that the water table has sunk to an extent that impedes regeneration (WCMC 1999).

"According to Duveyrier, extensive forests of this cypress ... have been almost completely destroyed for the sake of their timber which has largely been employed for house-building at Djanet and Rhat" (Dallimore et al. 1967).

Remarkable Specimens

The largest is said to be a tree called Tin-Balalan with a 12-meter girth, 22 m tall, which grows in Wadi Amazar (Werner and Bubriski 2007). Werner and Bubriski (2007) also report work by F. Abdoun using radiocarbon to estimate the age of a tree in Wadi Tichouinet at 2200 years old. The tree has a trunk diameter of 126 cm.

Ethnobotany

Its rarity is due to exploitation by native peoples. Nomads often shelter under the trees and their herds destroy any regeneration. There is still sporadic exploitation of living branches for firewood, but systematic cutting of the cypresses has been brought to an end by their rarity and remoteness. There were still many living trees in 1863 according to the first European report and they were still a major source of timber for local use (FAO 1986). Protection of the area has since virtually ended exploitation, except for ecotourism, a sustainable use (A. Farjon, pers. comm. Sep-2005). Nonetheless, the complete tree census, conducted between 1997 and 2001, found that cutting of branches and roots for firewood, and damage to trees from grazing goats, are likely responsible for the death of eight percent of the trees censused in 1972 (Abdoun and Beddiaf 2002, cited by Verner and Bubriski 2007).

This is one of the most drought-resistant species known, with considerable frost tolerance. The wood is suitable for most exacting uses, being of medium density, stable and aromatic. The stems are straight in cultivation and the branches fine. Growth is reportedly a little slower than that of Cupressus sempervirens in similar conditions. it could be a valuable species for planting in arid regions (FAO 1986).

The species has been used in dendrochronology. Verner and Bubriski (2007) report work by F. Abdoun showing that trees sometimes add more than one ring per year and in other years may not produce an annual ring; from this Abdoun et al. (2005) concluded that crossdating is not feasible in this species. Nonetheless Cremaschi et al. (2006) have constructed a long chronology based on subfossil wood and used it to reconstruct long-term climate variation in the region.

Observations

May only be seen in the wild in the Tassili N'Ajjer National Park, which has been designated a World Heritage Site. Tours visit the area regularly, chiefly to see spectacular pictographs in the area. The species has also been successfully established in cultivation (WCMC 1999).

Remarks

The epithet dupreziana commemorates the species' European discoverer, Captain Duprez, commander of French forces at Fort Charlet in the Djanet oasis, near the Tassili plateau. He wrote to a biologist, “I discovered one day in a small wadi called Tamrit a tree with foliage and habit too unusual for the area not to attract my attention.” That first tree found by Captain Duprez is thought to be still alive and healthy at the head of Wadi Tamrit (Werner and Bubriski 2007).

This is the only plant known to reproduce by cloning its male genetic material through a process known as male apomixis, in which pollen enters the ovules, but instead of combining with the female cells, divides internally to become a viable seed genetically identical to itself. "An experiment in which pollen from the Cupressus dupreziana was dusted onto the female cones of the Mediterranean cypress, whose resulting seeds were germinated and grown for 15 years, culminated in trees physically similar and identical in their DNA to the 'father' tree, but unlike the 'mother.' There is no obvious evolutionary advantage to this... as in all cloning, this would lead to an evolutionary dead end: genetic invariability and a species not capable of adapting to changing condition" (Werner and Bubriski 2007; see also publications by Pichot et al. listed below).

In a similar vein, "It was long known that only about 10 percent of seeds from both wild and cultivated Saharan cypress trees have a viable embryo, so the tree’s low fertility rate was thought to be intrinsic to the species. Pichot and el Maataoui recently determined exactly why: The tree’s meiosis—its cell division prior to reproduction—is wildly erratic. Instead of the pollen dividing neatly in half to create a pair of diploid cells, which contain two sets of chromosomes, it often creates cells containing one or four sets of chromosomes —or none. Only diploid cells can successfully germinate" (Werner and Bubriski 2007; see also publications by Pichot et al. listed below).

Citations

Abdoun, F. and M. Beddiaf. 2002. Cupressus dupreziana A. Camus: répartition, dépérissement et régénération au Tassili n'Ajjer, Sahara central. Comptes Rendus Biologie 325(1-11).

Abdoun, F., A.J.T. Jull, F. Guibal and M. Thinon. 2005. Radial growth of the Sahara's oldest trees: Cupressus dupreziana A. Camus. Trees 19:661-670.

Camus, A. 1926. Le Cupressus dupreziana A. Camus, Cypres Nouveau du Tassili. Bull. Soc. Dendrol. Franc. 58:39-44.

Cremaschi, M., M. Pelfini, and M. Santilli. 2006. Cupressus dupreziana: a dendroclimatic record for the middle-late Holocene in the central Sahara. The Holocene 16(2):293-303.

FAO Forestry Department. 1986. Databook on endangered tree and shrub species and their provenances. Rome: FAO. 524 pp.

Ramdani, M., O. Rached, T. Lograda and A. Aggoun. 2007. Genetic diversity in foliar terpinoids among natural populations of Cupressus dupreziana in Tassili n'Ajjer (Algeria). Asian Journal of Plant Sciences 6(8):1211-1216.

Silba, J. 1998. A monograph of the genus Cupressus L. Journal of the International Conifer Preservation Society 5(2):1-98.

[WCMC] World Conservation Monitoring Centre - Trees database. http://www.wcmc.org.uk/cgi-bin/SaCGI.cgi/trees.exe, accessed 1999.07.01, now defunct.

Werner, L. and K. Bubriski. 2007. A cypress in the Sahara. Saudi Aramco World 58(5):32-39. http://www.saudiaramcoworld.com/issue/200705/a.cypress.in.the.sahara.htm, accessed 2012.12.01, now defunct.