Vachellia nilotica (L.) P.J.H. Hurter & Mabb.
Mimosa nilotica L., Acacia nilotica (L.) Delile.
Eng.: Acacia, Egyptian mimosa, Egyptian thorn, red thorn, arab gum tree. Spa.: Acacia. Fre.: Gommier rouge, acacia d’Arabie, acacia à gomme. Ara.: Sunut, sunt, sant, habbat aâm, gharad, gharat, amur, amuur, amurayé (Hassanía), babul, tulh; the fruit: karat. Tamahaq: Tamat, tsant, taggart, tiggaert, tugger; the fruit: agga.
Tree up to 20 m in height, spiny, hermaphrodite, deciduous, with straight trunk and dense crown, umbrella-shaped or not. Trunk and main branches with rugose and fissured bark, brown or blackish-brown, which does not peel, and with a reddish exudate resin in wounds. Young branches olive green in colour, glabrous or hairy. Stipular spines, 0.5-8(15) cm, paired, diverging, usually straight, white or pale grey. Leaves 4-10(15) cm, alternate, bipinnate, with petiole 3-6(8) cm, and rachis with 3-10(14) pairs of pinnae —with 1 gland at the insertion of the pinnae—, each with 10-27(30) pairs of leaflets 1.5-7 × 0.5-1.5(2) mm, oblong, rounded at the apex, subsessile, glabrous or hairy, green. Inflorescences in spherical capitula, (6)12-15 mm in diameter, axillary, solitary or in fascicles of 2-4, pedunculate —peduncle 1.2-4.5 cm—, with numerous minute flowers, bright yellow. Calyx 1-2 mm, with puberulous teeth. Corolla 2.5-4 mm, with oblong lobes. Stamens numerous. Pod (8)10-15(20) cm × (12)15-22 mm, linear and compressed, or torulose —constricted and strangled between the seeds—, pendulous, straight or curved, from dark brown to greyish, glabrous or hairy, indehiscent, with 4-10(16) seeds. Seeds 6.5-9 × 5-8mm, ellipsoid, compressed, brown-blackish, smooth.
Flowering:
June to December.
Fruiting:
October to March (3-4 months after flowering).
Habitat:
Desert and semi-desert areas, in close proximity to watercourses and wadis.
Distribution:
The species is distributed throughout tropical and subtropical Africa, and the SW and southern Asia (up to India), but the 9 recognised subspecies have an unequal Distribution.
Observations:
Within the study area 4 subspecies are recognised.
V. nilotica subsp. nilotica, known from Mauritania and Egypt, has torulose pods —strongly constricted between the seeds—, glabrous (while they are hairy in the other subspecies), green at first, then yellowish, and finally balck.
V. nilotica subsp. tomentosa (Benth.) Kyal. & Boatwr. [Acacia arabica var. tomentosa Benth., A. nilotica subsp. tomentosa (Benth.) Brenan, Mimosa scorpioides L., A. scorpioides (L.) W.Wight, A. arabica (Lam.) Willd.] includes plants with pods also torulose, ± straight, brown or greyish. Central and southern Sahara, from the Atlantic to the Red Sea, the Sahel and tropical Africa to the 10th parallel.
V. nilotica subsp. adstringens (Schumach.) Kyal. & Boatwr. [M. adstringens Schumach., A. nilotica subsp. adstringens (Schumach.) Roberty], has pods that are ± curved and flattened, and are slightly constricted between the seeds, greyish. This subspecies has a similar distribution area to the latter, but in the studied area it is only known from the central Sahara (Algeria and Libya).
V. nilotica subsp. kraussiana (Benth.) Kyal. & Boatwr. [A. arabica var. kraussiana Benth., A. nilotica subsp. kraussiana (Benth.) Brenan], presents pods slightly constricted between the seeds, pubescent at first and then glabrescent, shinny black when mature in the part of the seeds, the rest of the pod dark grey or matt black. It was considered native to southern Africa but the population of V. nilotica in the Zag (Morocco), S of the Draa River, could be assigned to this subspecies.
Before deforestation accelerates, a profound revision of the African distribution of the different species of V. nilotica should be conducted. Brenam (1983) presented a good bio-geographic synthesis, but it is difficult to apply to current data.
Conservation status:
A relatively common and widespread species, not considered threatened. In the IUCN Red List of Threatened Species, it is listed as Least Concern (LC) at global level. In Algeria ti is included (as subsp. tomentosa) in the List of protected non cultivated flora (Executive Decree 12-03 on 4-Jan-2012). In Mali it is included in its List of species that need authorization for commercial use (Decree 07-155/P-RM of 2007).