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Conservation status

Juniperus procera

Hochstetter ex Endlicher 1847

Common names

African pencil cedar.

Taxonomic notes

Syn.: Juniperus hochstetteri Ant. 1857; Sabina procera (Hochst. ex Endlicher) Ant. 1857 (Farjon 1992).

Description

"Habit: tree, max. height 30-40 m, dbh 1.5 m, usually monopodial, exposed trees sometimes multistemmed or branching very low; branches of first order thick and long, ascending and crooked in old trees; branches of higher orders assurgent in young trees, but spreading and finally pendulous in old trees; crown pyramidal in young trees, mature trees soon broad, irregular and open, domed or flat-topped in savannahs and on windswept sites; bark at first smooth, very soon with papery flakes, purplish, on older trees fibrous, deeply longitudinally furrowed, peeling in long, narrow strips, pale brown or grey-brown. Foliage: branchlets in dorsiventral sprays (young trees) or more irregular, ultimate branchlets sometimes pinnately arranged, slender, quadrangular, 0-.6-1 mm diam., orange, but covered by light green leaves. Leaves: juvenile leaves temate or more or less decussate but remote, on seedlings and young trees, rarely on mature trees (but returning on coppiced trees!), acicular, widest at base, keeled, acute to pungent, 8-10 x 1 mm, epistomatic; mature leaves scale-like, decussate, imbricate, appressed at base only, (ob)lanceolate on older branchlets, up to 6 mm long, on ultimate branchlets triangular, 0.5-l mm long, acute, incurved but with free apices, margins entire; scale leaves amphistomatic, stomata in 2 or more inconspicuous tapering lines; glands linear-elliptic, conspicuous and active; a single resin cavity in each leaf; colour light green or yellowish-green. Male strobili: numerous on ultimate branchlets, solitary, terminal or subterminal, 3-5 x 2-3 mm, greenish, turning orange-brown; microsporophylls 10-12, peltate, with round, denticulate margins, bearing 2-3 pollen sacs. Female cones: solitary, subterminal and axillary on ultimate branchlets, sessile or short pedunculate; young strobili stellate-spheroid, c. 2 mm diam., bluish-green; mature cones globose, 3-7 mm diam., smooth, waxy, brown to purplish-black, bluish or pruinose; seed scales 4(-6), decussate, entirely fused, the two meeting at the distal pole the largest (2-5 mm long), with the bract entirely fused except for a minute dorsal triangular umbo (0.3 mm), interior of scales more or less woody, yellow. Seeds: ovules 1-2 per fertile scale; seeds (l-)2-3(4), angular-ovoid, 4-5 x 3-3.5 mm in largest cones, yellowish-brown" (Farjon 1992).

Distribution and Ecology

E Africa: NE Sudan near the Red Sea, the Ethiopian Highlands, in Djibouti, Somalia, Kenya, Uganda, Tanzania, in extreme eastern Congo Republic (Haut Katanga), Malawi, northeastern Zimbabwe; also in the mountains adjoining the Red Sea in Saudi Arabia and Yemen (Farjon 1992).

"Juniperus procera occurs in the mountainous regions and highlands of East Africa. ... This distribution coincides largely with the Eritreo-Arabian Subregion of Takhtajan (1986). The southernmost occurrence of the genus is in the Inyanga Mountains of Zimbabwe, but it is represented by a single (protected) tree only. Its altitudinal range in Africa is between 1050-3600 m, it occurs most commonly between 1800-2700 m. Rainfall is the predominant factor determining growth and occurrence; in East Africa it is most luxuriant where the rainfall averages 1000-1200 mm annually. Stunted trees are still found in savannahs with annual precipitation of only 400 mm. There is a dry season of at least five months duration. Conditions on the Arabian Peninsula are similar, but there is a more pronounced Mediterranean element in the pattern of moisture distribution; most rain falls in the cold season. J. procera is mostly a constituent of open evergreen sclerophyllous mountain forest, forming pure stands or more commonly mixtures with Podocarpus gracilior and with angiosperms (Olea, Nuxia, Erythrina, Agauria (tall Ericaceae), Afrocrania volkensii, Cussonia spicala, Xymalos monospora etc.). The broadleaf species become more dominant with increasing precipitation levels and above 1300 mm annual rainfall Juniperus is usually absent" (Farjon 1992).

Zone 9 (cold hardiness limit between -6.6°C and -1.1°C) (Bannister and Neuner 2001).

Big tree

Oldest

Dendrochronology

Not suitable. Although J. procera can produce annual growth rings, crossdating and radiocarbon dating of stem sections from a site in central-northern Ethiopia found that the growth rings are neither annual nor represent a common periodicity (Wils et al. 2009).

Ethnobotany

Observations

Raf Aerts (e-mail, 2002.01.03) reports that J. procera used to be a dominant species in the Tigray highlands of Northern Ethiopia (along with Olea europaea subsp. africana). Due to logging, very few stands remain. Some remnants can be found in the Dese'a state forest on the border between the Tigray and Afar regional states in Northern Ethiopia. Large individuals can be found scattered through the region in sacred groves or 'church forests'.

Remarks

"In Eurasia, an increased adaptation to continentality can be observed through the taxa J. excela subsp. excelsa, J. foetidissima, J. excelsa subsp. polycarpos and J. semiglobosa. The more equatorial distribution of J. procera ensures a less extreme range of seasonal temperatures, as well as a climate where more moisture is generally available. The distribution of at least two species is also generally connected with major orogenetic events. The East African distribution of J. procera concurs largely with the volcanic uplands adjacent to and associated with the Great Rift systems, along which this species has reached 18°08' S. J. semiglobosa, the most distinct species taxonomically, is a true high altitude species of the mountains in Central Asia. While it crosses a relatively important floristic barrier to the SE, its limit in that direction is nevertheless climatically determined. Increased precipitation levels prevent its eastward expansion, which may be of relatively recent date connected with the rapid uplift of the Karakoram Range (1500 m since the last ice age and still in progress); it is not known from Nepal. For the most part, the geographical ranges found for [these] taxa ... coincide well with the floristic (sub-)regions and provinces as defined by Takhtajan (1986)" (Farjon 1992).

Citations

Takhtajan, A. L. 1986. Floristic regions of the world (trans. T. Crovello). Berkeley: University of California Press.

Wils, Tommy H.G., Iain Robertson, Zewdu Eshetu, Ute G.W. Sass-Klaassen, and Marcin Koprowski. 2009. Periodicity of growth rings in Juniperus procera from Ethiopia inferred from crossdating and radiocarbon dating. Dendrochronologia 27(1):45-58.

See also

Farjon (2005) provides a detailed account, with illustrations.

Last Modified 2012-11-23