DATA SHEETS ON SPECIES UNDERGOING GENETIC IMPOVERISHMENT JUNIPERUS PROCERA Hochst. ex Endl. ¹

Compiled by J. B. Hall
Division of Forestry
University of Dar es Salaam
Morogoro, Tanzania

Juniperus procera Hochst. ex Endl. (1847), in Synopsis Coniferarum 26.

Synonymy: Sabina procera (Hochst.) Antoine
Juniperus abyssinica Hort.ex C. Koch

Vernacular Names: African Pencil Cedar; Mutarakwa
(Kikuyu, Kenya), Ol-tarakwa (Masai, Kenya and Tanzania), Tarakwet (Nandi, Kenya), Tedh (Amharic, Ethiopia)

Family: Cupressaceae

Botanical Description

An afromontane tree (White 1978), usually the tallest species present, reported to reach 50m (Poulsen 1975) though more commonly 30–35m. Bole straight but sharply tapered, often with a pronounced twist. Butt commonly heavily fluted. Diameter reaches 2m, sometimes up to 2.9m.

Bark: Pale brown to reddish brown, thin and fibrous, with shallow longitudinal fissures and exfoliates in thin, papery strips.
Branching: heavy, usually from near the ground.
Crown: pyramidal in youth, spreading in older trees.
Branchlets: slender, terete, 0.5–1 mm in diameter, bearing sessile, scale-like leaves in decussate arrangement.
Leaf: mature leaf grey or glaucous, about 1 mm long, acute, hooded and keeled at the apex and with a narrow transclucent margin and an elliptic oil gland on the back, near the base. Juvenile leaves in whirls of three on shoots, 1–2 cm long, linear and spinetipped, the lower part being decurrent on the branch. Oil gland on abaxial surface linear, extending three-quarters of the length of the leaf. The juvenile leaves are deciduous. As plant ages the leaves gradually change until foliage charactertic of mature tree is produced. The term “intermediate” is used to describe leaves not reduced to the adult form but with the characteristic decussate adult arrangement.
Inflorescence: Dioiecious. Male cones solitary, terminal on short branchlets, small (about 3 mm long), ellipsoid to subglobose in shape, yellowish in colour, consisting of 5–6 pairs of decussate, subpeltate, obtuse or blunt apiculate scales, each with 2–3 pollen sacs. Female cones solitary, terminate on short lateral shoots, consisting of 3–4 pairs of decussate fleshy scales, and bearing a solitary, erect ovule.
The species is anemophilous, producing vast quantities of pollen (Coetzee 1967). Fruit dispersal depends on animal vectors, presumably birds (Kerfoot 1964).
Fruit: Berry-like, globose or subglobose, reddish-brown to blue-black in colour, waxy and composed of the confluent, swollen, fleshy scales of the female cone, the tips of the scales just distinguishable. When ripe, 4–8 mm in diameter, containing 1–4 seeds with a woody testa, each flattened or triangular, brown and about 5 mm long. Additional 1–3 smaller, aborted seeds common.
Illustrations: see von Breitenbach (1963) p. 66; Dale & Greenway (1961) Fig.1; Eggeling & Dale (1951) Fig.24; Lewis (1960) Tab. 3A; Melville (1958) Fig. 5. See also Chapman & White (1970) Photos 13, 14, 15 & 16; Kerfoot (1964) Photos 1 & 2.

¹ Suggestions have been made (e.g. Lewis 1960; Kerfoot 1975) that this species is not separable from J. excelsa Bieb., the range of which extends to Central Asia. Here the traditional view of the African taxon is retained, pending wider formal acceptance of the broader concept proposed for J. excelsa.

Distribution and Ecology

Widely distributed from Arabia southward to Zimbabwe. Range fairly continuous in Ethiopia and Kenya; outlying isolated populations extend the range of the species to the Horn of Africa in the East and Zaire in the West. Outlying populations are also found in the south of the species range, south of latitude 4°30'S.

The species occurs in highland and mountain areas, about 1750m altitude; in particularly favourable niches it may occur as high as 3500m. Details on elevational range are complicated by interactions of temperature, extent of high ground and site. On isolated mountains and in other places where low temperatures prevail at unusually low elevations, the species has been reported to occur at only 1350–1400m.

J.procera occurs on rocks as diverse as limestones (Gilliland 1952), gneisses and granites of the Basement Complex (Chapman & White 1970) and basalts (Greenway 1955), but especially on the latter. The concentration of the tree on areas of volcanic rocks is a consequence of the history of its entry and spread into Africa; there is no direct evidence that it is restricted to certain types of rock.

In terms of soil type, there is little information but it is clear that the drainage must be good and that the species rarely grows in soil heavier than sandy clay. In other respects it appears tolerant of widely varying soils. Soil depth does not appear to be a critical factor.

The over-riding restricting climatic factor seems to be temperature, J.procera being restricted to sites with a mean annual temperature of below +19°C. In East Africa this corresponds to a minimum elevation of 1350–2000m. Further from the equator the minimum temperature tolerated by the species is reduced, the lower limit of mean annual temperature for the species being +7–10°C. A clear relationship exists between distribution of the species and rainfall, the optimum mean annual rainfall lying between 400 and 1200 mm. The tree will grow in higher rainfall areas under plantation conditions, when competing species are artificially supressed. In natural conditions, under rainfall regimes with 8 or more months receiving ≥ 50 mm of rain and with a mean annual rainfall of ≥ 1000 mm, J.procera is unable to compete with other species. Likewise, the species is not competitive in natural conditions in areas with a mean annual rainfall of 800–1000 mm and 5 or more dry months per year, with ≥ 50 mm rainfall. Where mean annual rainfall is below 800 mm, the tree seems to have become established in all sites with suitable temperatures that it has reached. At 600 mm mean annual rainfall, or less, the competitive advantage over other species is strongest. However, in areas with less than 600 mm of rainfall, the areas where the species can be found receive additional moisture from mist and low-lying clouds.

Potential Value

The wood of J.procera is fine-textured, straight-grained and of medium hardness. The heartwood is very resistant to termites (von Breitenbach 1963) and durable against rotting in the ground. It is easily worked, takes a good polish and glues and whittles well.

The main uses of the wood of J.procera are for construction, transmission and other poles, pencils, flooring and wooden structures exposed to the weather (von Breitenbach 1963; Ojiambo 1978). The wood is also used for furnishings, and there are some prospects for its use in the manufacturing of hardboard and particleboard (Utilization Section 1966). In addition to the above, Cedar Wood Oil was earlier distilled from the sawdust and used in the cosmetic industry (Dale and Greenway 1961).

Status

Outlying populations endangered. In Zimbabwe one single tree presently survies (Wild & Grandvaux Barbosa 1967); in Zaire and Malawi the numbers of trees remaining in many populations are very low (Robyns 1946; Chapman 1957; Kerfoot 1964, Chapman & White 1970).

Reasons for Decline in Area

Changing land use patterns, discontinuous distribution range of the species, coupled with wildfires hampering the establishment of regeneration; browsing pressure, particularly from buffalo and elephant; logging for both local use and for export (see e.g. Ojiambo 1978; Utilization Section 1966; Robyns 1946; Chapman 1957); the gradual switch from local species to fast-growing exotics in plantation forestry.

Protective Measures Recommended

Exploration and evaluation through the establishment of internationally coordinated, range-wide provenance trials, which are likely to promote conservation measures and the increased use of J.procera in plantation forestry.

Improved management practices in natural stands, protection of areas against fire and domestic and wild animals to enable natural regeneration.

Cultivation

Early in this century a number of plantations were established especially in Kenya, until attention switched to faster-growing species during the 1960s. Recently, however, interest in J.procera has revived and new plantings are under way in Tanzania; unlike the earlier plantings, there is more interest today in trying to identify good provenances.

Seed is readily available (Mugasha 1978) but has short viability: 6 to 12 months. 1 kg of seeds contains 42 750 kernels; the germination 6 weeks after collection is around 40% (von Breitenbach 1963).

Phenological information is limited but Mugasha (1978) reports seed available at Shume in the Usambaras (4°42'S, 38°12'E; 1860m) from January to May (i.e. the latter half of the rainy season) and on Mount Kilimanjaro, at Rongai (2°58'S, 37°27'E; 2130m) towards the end of July (i.e. the first half of the dry season).

Seedlings are ready to plant out after 1–2 years in the nursery (von Breitenbach 1963; Mugasha 1978). In the field, close initial spacing (2m × 2m) is advocated (von Breitenbach 1963) to limit low crown development, and form is further improved by a series of early prunings; in Tanzania these have been undertaken at 2.5, 5 and 6 years (Borota 1971b). Initial thinning in Tanzania has been 50% at 5 years. It is essential that weedings be carried out at least once a year during the establishment phase.

Borota (1971 a, b, 1975) and Mugasha (1978) have reported the following yield figures, registered in plantations in Tanzania at Kigogo (8°45'S, 35°15'E; 1800m a.s.l.) and Lushoto (4°47'S, 38°17'E; 1560m a.s.l.):

¹ Figures in parentheses are mean annual increments.

Bibliography

Borota, J. (1971a). The growth of the tree species at Kigogo arboretum. Tanzania Silviculture Research Note, 20, 1–7.

Borota, J. (1971b). The growth of tree species in Lushoto arboretum. Tanzania Silviculture Research Note, 23, 1–24.

Borota, J. (1975). Provenance studies of the major and economically important species in Tanzania. Zbornik Vedeckych Prac, 17, 99–119.

Breitenbach, F. von (1963). The Indigenous Trees of Ethiopia, 2nd edn. Ethiopian Forestry Association, Addis Ababa.

Brenan, J.P.M. & Greenway, P.J. (1949). Tanganyika territory. Check lists of the Forest Trees and Shrubs of the British Empire, 5, 1–653.

Chapman, J.D. (1957). The Indigenous Conifers of Nyasaland. Nyasaland Department of Forestry.

Chapman, J.D. & White, F. (1970). The Evergreen Forests of Malawi. Commonwealth Forestry Institute, Oxford.

Coetzee, J.A. (1967). Pollen analytical studies in East and Southern Africa. Palaeocology of Africa, 3, 1–146.

Dale, I.R. & Greenway, P.J. (1961). Kenya Trees and Shrubs. Buchanan Estates, Nairobi.

Eggeling, W.J. & Dale, I.R. (1951). The Indigenous Trees of the Uganda Protectorate, 2nd edn. Government Printer, Entebbe.

Gilliland, H.B. (1952). The vegetation of eastern British Somaliland. Journal of Ecology, 40, 91–124.

Greenway, P.J. (1955). Ecological observations on an extinct East African volcanic mountain. Journal of Ecology, 43, 544–563.

Kerfoot, O. (1964). The distribution and ecology of Juniperus procera Endl. in east central Africa, and its relationship to the genus Widdringtonia Endl. Kirkia, 4, 75–86.

Kerfoot, O. (1975). Origin and speciation of the Cupressaceae in southern Africa. Boissiera, 24, 145–150.

Lewis, J. (1960). Gymnospermae. (Flora Zambesiaca, 1, 79–88.

Melville, R. (1958). Gymnospermae. (Flora of Tropical East Africa ed. by W.B. Turrill & E. Mihne-Redhead). Crown Agents, London.

Mugasha, A.G. (1978). Tanzania natural forests' silvicultural research - review report. Tanzania Silviculture Technical Note (New Series), 39, 1–41.

Ndosi, O.M. (1980). Some factors affecting the Regeneration of Juniperus procera in Arusha National Park, Tanzania. Unpublished special project report, Division of Forestry, University of Dar es Salaam.

Ojiambo, J.A. (1978). The trees of Kenya. Kenya Literature Bureau, Nairobi.

Poulsen, G. (1975). Silviculture practices in montane forest areas. Unpublished manuscript, Division of Forestry, University of Dar es Salaam.

Robyns, W. (1946). Sur l'existence du Juniperus procera Hochst. au Congo Belge. Bulletin du Jardin Botanique de Etat, 18, 125–131.

Utilization Section (1966). Timbers of Tanganyika: Juniperus procera (African Pencil Cedar). Utilization Section, Forest Division, Moshi.

White, F. (1978). The Afromontane region. Biogeography and Ecology of Southern Africa (Ed. by M.J.A. Werger), pp. 463–513. W. Junk, The Hague.

Wild, H. & Grandvaux Barbosa, L.A. (1967). Vegetation Map of the Flora Zambesiaca area, 1:2 000 000. Supplement to Flora Zambesiaca.