Cupressaceae

Cupressus dupreziana var. dupreziana

Native to the Sahara Desert in Algeria where it occupies a narrow strip of about 120km long on the edge of Tassili Plateau. It is Critically Endangered due to grazing and cutting for firewood

Description

Habit

Tree 16–18m tall, monoecious; trunk d.b.h. 2–3m. Bark thick, deeply fissured, exfoliating in longitudinal strips. Branches spreading or ascending, forming a conical or pyramidal crown.

Foliage

Spreading or drooping to pendulous. Leaves, scale-like (all equal in size), arranged in opposite pairs at right angles to those above or below, overlapping, gradually tapering, with glands, stomata few and scattered on margins near leaf base; shiny greyish-green or glaucous green.

Cones

Male pollen-cones on branches close to female seed-cones, solitary, terminal, ovoid, 4–6 x 2–3mm, yellowish-brown when mature. Female seed-cones solitary on lateral branches, terminal on short leafy branchlets, ovoid-oblong, 15–27 x 13–21mm, light brown when mature; bract-scale complexes ca12 in opposite pairs at right angles to those above or below. Seeds 6–8mm, closely packed, ovoid-globose, flattened, dark brown, wings 2 on opposite sides, 1–2mm wide.

Notes

This variety and C. dupreziana var. atlantica have in the past been recognised as distinct species: C. dupreziana A. Camus and C. atlantica Gaussen. The differences between these are very small in that C. dupreziana var. atlantica differs by having globose to ovoid-globose seed cones with 10–12 bract-scale complexes and the seeds are more or less angular.

Distribution

Endemic to Algeria where it occurs to the south-west edge of the Tassili Plateau within the geographical Regions of Maddak, Tassili-Hedjirit and Amiok. Here it has an altitudinal range of between 1430 and 1830 m with an extent of occurrence (EOO) of 1000km² (Abdoun & Beddiaf, 2002). Its range occupies a strip of 120km in length and between 6 and 15km wide and contains 46 sites. The area of ocupancy has not been calculated but is likely to be much less than 500km² given the small total population size and restricted habitat.

Up until the 1940s it was thought that there were no more than ten living individuals, however by 1949 the population estimate increased to 200 (Abdoun & Beddiaf , 2002), although for a long time the original number of 10 was still widely believed and quoted. Between 1971 and 1972 Säid Grim counted 230 living trees and numbered each one – these numbers still remain on the trees today. An inventory between 1997 and 2001 conducted by Abdoun and Beddiaf discovered that 20 of the 230 trees had died but they added 23 new individuals making a total of 253 individuals. The current population size is therefore 233 living trees, in varying states of health. Tamghit (24°38’ N) and Ellidj (24°55’ N) the population exist as a few scattered individuals which survive by clinging to the mountainsides or hidden in the ravines, while, north and south of this zone trees occur in groups of four to fifteen together, mostly confined to the less accessible wadis (Abdoun & Beddiaf, 2002). The distance between trees varies from 1 metre to 10 kilometres and their density, from a standing tree to about thirty. The trees with a circumference of between 3 to 4 m are estimated to be between 1200 and 2300 years of age (Abdoun et al., 2005). The population decline is estimated to be 8% over a period of 30 years (Abdoun & Beddiaf, 2002).

Habitat and Ecology

The trees grow on the summits of mountains or in the bottoms of valleys and gorges, where precipitation is estimated to be 30mm per year (Dubief, 1963). Sixty-eight percent of the trees are located in Wadi beds, 22% in rock (palaeozoic sandstone) fissures and 8% on ridges. Due to the present mutilated condition of most trees, it is not possible to characterise exactly the most favourable conditions for the species. It is in the rocky areas with little apparent soil that we find the greatest number of cypresses with their typical pyramidal shape. Phytosociologically the cypress is merely regarded by some authors (Leredde, 1957, Benhouhouh et al., 2005) as a companion species as it appears to have no link with the current surrounding flora. A phytohistorical study, based on charcoal, showed that approximately during the mid-Holocene time, that in this region were found Pistacia atlantica with Olea europaea ssp laperrinei (Abdoun 2002, 2006a). The height of trees varies between 3 and 22m, their circumference between 0.32 and 12m. A good number of these trees have developed fastigiated or pyramidal crowns.

The potential for natural regeneration had been considered absent until the discovery of two new individuals with circumferences of 32 and 37cm (Abdoun & Beddiaf, 2005). In its juvenile stage this cypress shows remarkable growth vigour. Radial incremental measurements taken showed an increase from 0.38 to 2.23mm per year in trees with circumferences between 0.8 to 2.2m, and increments from 0.08 to 0.14mm per year in trees of medium height relative to the entire population (3 to 7m) of which ages are estimated to range from 600 to 2000 years (Abdoun, 2005).

Human Uses

The wood was highly valued for construction and carpentry in the past. The main use now is for fuel.