Vachellia tortilis (Forssk.) Galasso & Banfi
Mimosa tortilis Forssk., Acacia tortilis (Forssk.) Hayne
Eng.: Karamoja, acacia, umbrella thorn. Spa.: Acacia. Fre.: Acacia, gommier, faux gommier. Ara.: Talha, talh, talihe, talhaya, hares, amrād, tahi, salam, (Egypt): seyal, sayyal. Tam./Tamahaq: Tamat, talha, tadjdjart, absor, abzac, abser, absegh, abzec, afagag, tafagak; the fruit: amalaga, tahasha. Spiny acacias of the género Vachellia in general issarher (in the Ahaggar massif) and kinba (in the Aïr).
Tree up to 14(20) m in height, spiny, hermaphrodite, deciduous, branched from the base and ± umbrella-like, or with a well defined, straight or somewhat tortuous trunk, and slightly irregular crown. Trunk with a greyish-brown bark, fissured longitudinally, that peels into elongated scales. Branches extended, highly branched, smooth, older branches brown-greyish, younger branches reddish-brown, and branchlets of the current year greenish-reddish, glabrous or hairy, with lenticels. Stipular spines (0.5)2-10 cm, paired, divergent, straight or slightly curved backwards, at first of the same colour as the branchlets turning whitish or white. Leaves 1-4.5 cm, alternate or in fascicles at the nodes, bipinnate with petiole 2-15 mm, and rachis with 2-8(10) pairs of pinnae -with 1 gland at the insertion of the pinnae-, each with 4-15(20) pairs of leaflets (1)2.7 × 0.6-1.2 mm, oblong or oblong-linear, with rounded apex and base, subsessile, entire, glabrous or hairy, dull green in colour, glaucescent on both sides. Inflorescences in spherical capitula, (4)7-12 mm in diameter, axillary, solitary or in groups of 2-5, pedunculate -peduncle 1.5-3 cm, glabrescent-, with numerous minute flowers, white or whitish-yellow. Calyx 1.5-2 mm, with glabrous teeth. Corolla 1.5-3 mm, with 5 ovate lobes. Stamens very numerous. Pod 3-15 cm × 5-9 mm, linear, highly compressed, slightly constricted between the seeds, glabrous or hairy, green at first turning a pale orange, brown or blackish, with irregular longitudinal striations, twisted into a spiral at maturity -sometimes making a full circle, sometimes more than one- with 6-12 seeds. Seeds 3-7 × 2-6 mm, ellipsoid, compressed, brown-blackish, smooth.
Flowering:
Late summer (August to October) and sometimes in winter (December to May).
Fruiting:
About 3-4 months after Flowering.
Habitat:
Plains, gentle slopes and depressions in semidesert and desert areas, in not very extreme climates, and in savannahs. From almost sea level to 2,000 m altitude in the Saharan mountain ranges.
Distribution:
The species is distributed across northern, eastern and southern Africa. The subspecies represented in the territory are distributed in the Sahara and the Sahel, while the other subspecies without representation therein are those with an eastern distribution [subsp. spirocarpa (Hochst. ex A.Rich.) Kyal. & Boatwr. (Acacia spirocarpa Hochst. ex A.Rich.)] and a southern distribution [subsp. heteracantha (Burch.) Kyal. & Boatwr. (A. heteracantha Burch.)].
Observations:
In the territory 2 subspecies can be recognised. V. tortilis (Forssk.) Galasso & Banfi subsp. tortilis, which are trees branched from the base, umbrella-like, with branches, leaves and pods hairy, leaves with (4)5(8) pairs of pinnae, each with (4)10(12) pairs of leaflets 1-2(3) mm, and spines (0.5-)2.5(5) cm, hairy, inflorescences 4-7 mm in diameter and pods 3-9 cm × 5-6 mm, with seeds 3-4 × 2-3 mm. In the territory of this project it occurs in Egypt (including the Sinai Peninsula) and Sudan, as it is a native species from eastern Africa and the Arabian Peninsula. Much more abundant and distributed throughout the territory is V. tortilis subsp. raddiana (Savi) Kyal. & Boatwr. [A. raddiana Savi, A. tortilis subsp. raddiana (Savi) Brenan]. A tree with distinct trunk and irregular crown, branches, leaves and pods glabrous, leaves with 2-6 pairs of pinnae, each with 6-15 pairs of leaflets 2-7 mm, and spines (0.5)2-10 cm, white, sometimes slightly recurved, with inflorescences 4-12 mm in diameter and pods 6-15 cm × 6-9 mm, with seeds 5-6 × 3.5-4 mm. This subspecies is broadly distributed throughout the entire Sahara and the Sahel. In large areas of the Sahara, this is the dominant tree species; it is of great importance as a protector of soils, humidity and biodiversity. However, at least during the past century, it has been disappearing, with little regeneration, not so much due to climate change, but as a direct consequence of human action. Trees are cut or pulled out because they are considered a nuisance for projects of alleged “progress”. Or they have been slowly and progressively eliminated for decades because their roots and bark have numerous medicinal properties and are used for their tannins. Also, their wood is used for coal and as fuel, and their branches, being very spiny, are cut to build fences. However, the main cause for the decline of the species is overgrazing, which hampers regeneration.
Its protection is much needed and its natural regeneration should be promoted, in the medium and long term, to stop desertification. In reforestation projects in the less arid areas of the northern and central belts of the Sahara, this should always be the most used species (although not the only one, since there are other native arboreal species of unquestionable importance, such as V. flava). In the southern belt of the Sahara, it should also be planted on a large scale, but here it should share its central role with other tree species that are native to the Sahel.
Conservation status:
A relatively common and widespread species, but becoming every day scarcer in spite of its unquestionable economic and ecological value. In the IUCN Red List of Threatened Species, it is listed as Least Concern (LC) at global level. In Algeria it is included in the List of protected non cultivated flora (Executive Decree 12-03 on 4-Jan-2012). In Tunisia it is included as Acacia raddiana in its List of native species that are rare and threatened with extinction (Order of the Ministry of Agriculture and Water Resources, 19-July-2006). In Mali it is included in its List of species that need authorization for commercial use (Decree 07-155/P-RM of 2007).