Since this is one of the few timber species of the Arabian deserts, it is suspected as being the wood from which the Biblical Ark of the Tabernacle was made. Kaplan (1979) says rather emphatically it is the Shittim of the Bible, which provided the Israelites with the large-size timbers for the Ark. The timber is also used for fenceposts, firewood, furniture, and wagonwheels. The prolific pods made good fodder for desert grazers and the foliage is also palatable, being one of the major dry season fodder trees for the Sahara-Sahelian belt. Bark, used for string in Tanganyika. Gum used as a poor man's gum arabic, said to be edible. It is the tree most recommended for reclaiming dunes in India and Africa (Roy et al, 1973). The thorny branches are used to erect temporary cages and pens. Bark said to be a good source of tannin (Roy et al, 1973). Africans once strung the pods into necklaces. Senegalese use the roots for spear shafts, Lake Chad natives use the stems for fish spears. African nomads often use the flexible roots for frameworks of their temporary shelters.
While I find few data specific to this species, I suspect that the gum is used like that of gum arabics in folk remedies. In French Guinea, the bark is used as a vermifuge and dusted onto skin ailments (Dalziel, 1937).
Pods contain close to 19% protein (Palmer and Pitman, 1972). NAS (1979) reports unconfirmed allegations that the foliage can be toxic to livestock. Certainly HCN has been reported in several Acacias. The following tables are reproduced, with permission, from FAO's Tropical Feeds (1981):
Nutritive tables (Gohl, 1981)
|
| As % of dry matter |
| DM | CP | CF | Ash | EE | NFE | Ca | P | Ref. |
| Fresh leaves, South Africa |
| 19.2 | 11.6 | 8.7 | 6.1 | 54.4 | 2.27 | 0.17 | 213 |
| Pods, South Africa |
| 17.3 | 24.8 | 5.7 | 3.1 | 49.1 | 0.79 | 0.34 | 213 |
| Seeds, South Africa |
| 37.8 | 10.9 | 5.9 | 6.0 | 39.7 | 0.56 | 0.73 | 213 |
| Pod husks, South Africa |
| 8.7 | 34.3 | 6.2 | 1.6 | 49.2 | 1.10 | 0.14 | 213 |
Acacia tortilis (Forsk.) Hayne subsp.
heteracantha (Burch.) Brenan
|
| As % of dry matter |
| DM | CP | CF | Ash | EE | NFE | Ca | P | Ref. |
| Fresh leaves, Sudan | 90.9 | 13.3 | 9.4 | 9.6 | 8.3 | 59.4 | 4.00 | 0.15 | 64 |
| Pods, Tanzania |
| 12.3 | 22.4 | 5.6 | 1.8 | 57.9 | 0.98 | 0.24 | 166 |
| Pods, Kenya |
| 17.8 | 17.5 | 8.4 | 1.7 | 54.6 | 1.34 | 0.36 | 129 |
|
| Digestibility (%) |
| Animal | CP | CF | EE | NFE | ME | Ref |
| Pods | Cattle | 46.2 | 42.0 | 74.0 | 76.6 | 2.30 | 166 |
Acacia tortilis (Forsk.) Hayne subsp.
spirocarpa (Hochst. ex A. Rich) Brenan
Medium umbrella-shaped tree 4–15 m tall, often with several trunks, reduced to a small wiry shrub less than 1 m tall under extremely arid conditions. Two types of thorns abound (1) long, straight, and white, and (2) small, hooked, and brownish. Leaves up to 2.5 cm long with 4–10 pairs of pinnae, each with ca 15 pairs of minute leaflets. Flowers white, aromatic, in small clusters. Pods flat, glabrose, coiled into a spring-like array.
Reported from North African and Middle Eastern Centers of Diversity, Umbrella Thorn, or cvs thereof, is reported to tolerate alkalinity, drought, heat, sand, slope, and stony soils. It seems to be more frost tolerant than
Prosopis juliflora, still plants less than 2 years old are easily damaged by frost. Four subspecies are known in different ecological zones: subspecies
tortilis—Sahel, Middle East; subspecies
raddiana—Sudan, Middle East, Sahel(2n=104); subspecies
spirocarpa—Eastern Africa, Sudan; and subspecies
heteracantha—Southern Africa (2
n= 52). The different subspecies seem to have different ecological tolerances, which is important to consider when choosing a subspecies for plantations. (2
n= 52, 104)
Native to much of Africa and the Middle East, this species has been introduced in many arid parts of the world. Ironically, it grows faster in the Rajastan Desert of India, where used for charcoal, firewood, and fodder, than in its native Israel (Kaplan, 1979). In Malawi, this species is already scorned by the rural public because it is thorny and difficult to work with. It is being tried for fencings (Nkaonja, 1980).
Deemed the most promising of 56 Acacia species tried at Jodhpur, India. Probably ranging from Subtropical Desert to Dry through Tropical Desert Scrub to Very Dry Forest Life Zones, umbrella tree is reported to tolerate annual precipitation of 1 to 10 dm, estimated annual temperature of 18 to 28°C, and pH of 6.5 to 8.5. This species tolerates hot, arid climates with temperatures as high as 50°C subspecies
raddiana grows where minimum temperatures are close to 0°C. It is best adapted to the lowlands. It thrives where rainfall is up to 1,000 mm. However, it is also extremely drought resistant and can survive in climates with less than 100 mm annual rainfall with long, erratic dry seasons. The tree favors alkaline soils. It grows fairly well in shallow soil, less than 0.25 m deep, though it develops long lateral roots that can become a nuisance in nearby fields, paths, and roadways. In shallow soil, the plants remain shrubby and must be widely spaced to allow for their lateral root growth.
For good seed germination, seeds should be treated with concentrated sulphuric acid for 30 minutes (Roy et al, 1973). Artificial regeneration aiming at large-scale nursery production requires full use of the germination capacity of the available seeds. This may be achieved by sulfuric acid pretreatment, which brings about the germination of all viable seeds. Treatment with boiling water is selective and mainly breaks the dormancy of bruchid-infested seeds, some of which are no longer able to germinate. Sowing of unripe seeds without pretreatment may be called for as an emergency measure in case of very severe infestation, to achieve at least partial success. Prior to storage, seeds should be fumigated to arrest progressing deterioration of seed viability by bruchids (Karschon, 1975). NAS (1980a) recommends dipping the seed in hot water to soak overnight. Seedlings require initial weeding to facilitate faster growth. Plantations can be spaced at 3 x 3 m.
Firewood harvested as needed, but 10-year rotations are suggested. In Jodhupr, flower initiation is ca May-June in 3-year old trees, fruits forming in July but ripening from November through February. Since the tree coppices well, there is no need to replant after every harvest.
Eleven-year old trees in deep sandy soils at Jodhpur averaged 6.4 m tall and 14 cm DBH. In shallow sandy loams over hardpan at Pali, India, 7-year old trees (98% survival) averaged 4.8 m tall, and 10 cm DBH. In sanddunes at Barmer, India, 5-year old trees averaged 3 m tall, 7 cm DBH. An average tree yields 6 kg pods of which 2.6 kg is clean seed. One tree is said to yield 14–18 kg pods and leaves per year in India (Muthana and Arora, 1980).
Acacia tortilis has been reported to yield giraffe forage at 5 MT/ha/yr.
A 12-year-old plantation in India yielded 54 MT fuel , suggest, annual returns of 4.5 MT, not a bad return for the desert (NAS, 1980a). The heartwood has calorific value of 4,400 kcals/kg, making superior firewood and charcoal. It is one of the main firewood and charcoal sources in parts of Africa, e.g. around Khartoum. Nitrogen-fixing nodules are reported in South Africa and Zimbabwe.
Bruchids often damage or destroy the seeds, on the tree or after collecting. Herbivores, tame and wild alike, are liable to graze seedlings and innovations. Trees attacked by beetles, mimosoid blights, and caterpillars. The wood is susceptible to termites. In Tanzania, elephants which eat the bark are wiping out some park populations. In Israel, the native Acacias host several species (>40) of mostly monophagous insects, whereas on one exotic, Australian
Acacia saligna, only a few polyphagous species occur (Halperin, 1980). Only
Microcerotermes diversus and
Kalotermes flavicollis, which feed on woody parts of both Acacias and
Apate monachus (a beetle which tunnels the stems and branches, causing them to collapse in windblow), may seriously damage the tree. In nature, regeneration and spread of Acacias are probably limited by bruchids destroying much of the seed crop. Seedlings from natural regeneration may come from damaged seeds with a still intact embryo axis, since seedcoat dormancy is removed by the effect of exit holes permitting rapid water absorption and germination. Intact seeds with hard impermeable seedcoats may require a long time to germinate, and probably function as a reserve to ensure the survival of the species (Karschon, 1975).
- Dalziel, J.M. 1937. The useful plants of west tropical Africa. The Whitefriars Press, Ltd., London and Tonbridge.
- Gohl, B. 1981. Tropical feeds. Feed information summaries and nutritive values. FAO Animal Production and Health Series 12. FAO, Rome.
- Halperin, J. 1980. Forest insects and protection in the arid zones of Israel. J. Israel For. Assoc. 30(3/4):68–72.
- Kaplan, J. 1979. Some examples of successful use of Acacia for afforestation. J. Israel For. Assoc. 29(3/4):63–64.
- Karschon, R. 1975. Seed germination of Acacia raddiana Savi and A. tortilis Rayne as related to infestation by bruchids. Ag. Res. Org. Leaflet 52. Bet Dagan.
- Muthana, K.D. and Arora, G.D. 1980. Performance of Acacia tortilis (Forsk) under different habitats of the Indian arid zone. Ann. Arid Zone 19(1/2):110–118.
- N.A.S. 1979. Tropical legumes: resources for the future. National Academy of Sciences, Washington, DC.
- N.A.S. 1980a. Firewood crops. Shrub and tree species for energy production. National Academy of Sciences, Washington, DC.
- Nkaonja, R.S.W. 1980. Dryland afforestation problems in Malawi. J. Israel For. Assoc. 30(3/4):100–105.
- Palmer, E. and Pitman, N. 1972. Trees of Southern Africa. 3 vols. A.A. Balkemia, Cape Town.
- Roy, A.D., Kaul, R.N., and Gyanchand. 1973. Israeli babool a promising tree for arid and semiarid lands.
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