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Acacia cyclops A. Cunn. ex G. Don

Mimosaceae
Rooikrans

Source: James A. Duke. 1983. Handbook of Energy Crops. unpublished.


  1. Uses
  2. Folk Medicine
  3. Chemistry
  4. Description
  5. Germplasm
  6. Distribution
  7. Ecology
  8. Cultivation
  9. Harvesting
  10. Yields and Economics
  11. Energy
  12. Biotic Factors
  13. References

Uses

Producing a dense high quality firewood, this species has been recommended for stabilization of coastal dunes. Goats and antelope browse the phyllodes. The seeds and their oily funicles are eaten by birds, primates, and rodents, and if crushed, might be suitable for cattle.

Folk Medicine

With its high tannin content, the species could serve as an astringent.

Chemistry

Bark has yielded 6.5% tannin, or in Natal, up to 12.1%. Seed contains 10% of fixed oil, the aril or funicle 40%.

Description

Dense, evergreen bushy shrub, often multistemmed, or small tree 3 to 8 m tall, with a rounded crown . In windy coastal sites it forms a hedge less than 0.5 m high. The foliage comprises light green phyllodes, varnished when young, and growing in a downward vertical position. Pods, maturing in summer, are not shed, but remain on the tree, exposing the seeds to predators and dispersers.

Germplasm

Reported from the Australian Center of Diversity, Acacia cyclops is reported to tolerate drought, salt, sand, weed, and wind.

Distribution

Native to southwestern Australia, where it grows mostly on coastal sand dunes. Used for stabilization in South Africa, it is spreading on sand and sandstone into coastal bush and heathland. This is an extremely weedy species spread by birds into indigenous vegetation. Once established, it is difficult to remove or replace. There is little vegetation cover beneath an Acacia cyclops thicket. The seeds remain viable in the soil for many years. It is relatively slow growing.

Ecology

Acacia cyclops can grow in dry areas with annual precipitation less than 300 mm. Tolerating salt spray, wind, sand-blast, or salinity, it is useful for dune stabilization. This species has a high light demand; it will not survive in deep shade. Monthly temperature means within the distribution range of this species vary from 5°C in winter to 31°C in summer. It is slightly resistant to frost. The species is generally found below 300 m altitude where annual rainfall is 200 to 800 mm. It grows on quartzitic or calcareous sand or limestone. It also is found in drier sites such as dune crests (NAS, 1980a).

Cultivation

Direct sowing of pretreated seed is recommended (NAS, 1980a). Seed are treated with abrasion, acid, and hot water treatment.

Harvesting

Trees may be harvested as needed. This species rarely coppices, and mature trees do not survive felling. The pods are nondeciduous and are therefore not easily gathered. Unlike many Acacia species, it is not considered a valuable tannin or gum producer (NAS, 1980a).

Yields and Economics

Standing biomass of Acacia cyclops in the southwestern cape of Africa, where it is replacing indigenous Fynbos vegetation and coastal shrub communities, was 131 MT/ha. Of this, the litterfall was said to represent 7.4% of the total biomass, 21.2% of the canopy mass.

Energy

Recommended by the NAS (1980a) as a firewood source. The wood is dense, the logs rarely exceeding 20 cm in diameter. It is a very popular firewood in South Africa, sold regularly in Cape Town. The annual litterfall of four Acacia species naturalized in the South African Cape, comprising 60% foliage and 30% reproductive structures, averages 7 MT/ha, double the value expected in evergreen scrub communities in winter rainfall regions. Standing biomass in the Acacia thickets is ca 10 times greater than that of mature Fynbos (11–26 MT/ha) and shrublands in other Mediterranean climates (15–30 MT/ha). Acacias lose ca 10% of their standing crop annually as litter, at a rate 3–4 times that of the Mediterranean heath and shrub communities. The litter accumulates on the ground. In a mature thicket, the dry mass of the ground litter per unit area exceeds that of the living canopy. The ground litter layer runs 14–28 MT/ha, which is fairly average by world standards. "The annual nitrogen and phosphorus input by Acacia litter should be about nine times as great per unit area as that of Fynbos." Assuming an N content of 1.5% and a P content of 1.13%, Acacia litter would contribute 105 kg N/ha and 92 kg P. In an area where the annual precipitation averages between 500 and 750 mm/yr and the annual temperature average ranges between 16 and 18°C, with radiation averaging 450–500 Langleys/day (Capetown has an average annual precipitation of ca 600 mm, average temperature approaching 18°C), the total annual litterfall is 9,680 kg/ha, with 1.4% as flowers, 35.5% as pods, 5.3% as seed, 11.3% as twigs, 39.0% as phyllodes, and 7.7% unidentified fragments. The total standing biomass was 131 MT/ha DM, ˜±4% (Milton, 1981).

Biotic Factors

Most African Acacias are thought to be cross pollinated. Pests and diseases are not an important factor in South Africa; in fact, the lack of seed destroyers is partly responsible for the weediness of the species. Grazers may damage seedlings.

References

Complete list of references for Duke, Handbook of Energy Crops
Last update December 16, 1997