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Acacia auriculiformis A. Cunn.

Mimosaceae
Darwin Black Wattle

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 unpublished.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

Used for fuelwood plantations as an ornamental and shade tree, quite tolerant of heat, the Australian species is widely planted in Oceana and southeast Asia. The wood is also employed for making farm tools and furniture (NAS, 1983a). Recent Australian tests suggest that 10-year old trees can be pulped readily by the sulfate process, giving high pulp yields, with good strength properties. Also produces high quality pulp by the neutral sulfite semichemical process. The tannin produces a good quality leather, inclined to redden upon exposure to sunlight (NAS, 1980a). The plant is amazing in its ability to recolonize wastes, papermill sludge, pH ca 9.5; even uranium spoils, pH ca 3.0; the only tree found on 20-year old uranium spoil. Used for the cultivation of the lac insect in India.

Folk Medicine

No data available.

Chemistry

The gum contains 5.3% ash, 0.92% N, and 1.68% methoxyl, and ca 27.7% uronic acid. The sugar from the gum after hydrolysis, contained 10.1% 4-0-methylglucuronic acid, 17.6% glucuronic acid, 59% galactose, 8% arabinose, and 5% rhamnose (Anderson, 1978). Bark contains ca 13% water.

Description

Resilient, vigorously growing, crooked or gnarled deciduous or evergreen tree, possibly attaining 30 m height, 60 cm DBH. Leaves alternate, simple flattened phyllodes, lanceolate or oblong, arcuate, long-attenuate at both ends, 10–16 cm long, ca 1.5–2.5 cm broad, thick coriaceous, glabrous with several long parallel veins from the base. Spikes 5–8 cm long, paired at the leaf bases. Flowers sessile, ca 3 mm long, the calyx glabrous, 5-toothed, the 5 petals ca 2 mm long. Stamens numerous, filiform, ca 3 mm long. Ovary pubescent, the style filiform. Pods 6–8 cm long, 1–1.5 cm broad, flattened but coiled. Seeds several, flattened-ellipsoid, ca 5 mm long, with a reddish or orangish aril (Little, 1983). Seeds 53,000–62,000/kg.

Germplasm

Reported from the Australian Center of Diversity, Acacia auriculiformis, or cvs thereof, is reported to tolerate alkalinity, desiccation, drought, fire, high pH, laterite, poor soil, sand dunes, and savanna. It is intolerant of hurricane, shade, and weeds, at least in early stages. Once established, the tree is quite competitive with weeds. Though somewhat tolerant of fire, it is not so resistant as Eucalyptus. (2n = 26)

Distribution

Native to the savannas of New Guinea, islands of the Torres Strait, and northern Australia, it has been widely introduced, e.g. in Fiji, India, Indonesia, Java, Malaysia, Niger, Nigeria, Philippines, Tanzania, Thailand, the Soloman Islands, Uganda, and Zanzibar.

Ecology

Estimated to range from Subtropical Moist to Wet through Tropical Dry to Wet Forest Life Zones, Acacia auriculiformis is reported to tolerate annual precipitation of 7.5 to 27 dm, annual temperature of 26 to 30°C, and pH of 3.0 to 9.5. With practically no maintenance it will grow on a wide range of deep and shallow soils, compacted clays, coral soils, laterites, limestone, mica schist, mine spoil, podzols, even sand dunes and unstable slopes.

Cultivation

It has been suggested as an interplant with long-term timber Dalbergias, itself serving as a short-term but renewable firewood source. Seeds, storable for 18 months in airtight containers, should be soaked in hot water for 24 hours. Sow in full light, allowing 6 days for germination (ca 80% germination after 2–4 weeks). To reforest grassland, burn and plant in holes ca 36 x 30 x 30 cm, spaced at 1–2.5 or 1–3 m if intercropped with Cassia siamea. Recent spacings have been 2.5 x 2.5 m.

Harvesting

In Indomalaysia, stands are operated on 10–12 year rotations. Trees coppice poorly. Indonesians have gotten some coppice when trees are cut at least 50 cm above the ground. When trees are felled, there is usually a swarm of seedlings, so cutover stands regenerate readily.

Yields and Economics

With rainfall at 2700 mm, at 3 years, average height of a stand with 1010 trees/ha was 12.4 m, average diameter 12.2 cm, standing wood volume 73.2 m3/ha; at age 4, 13.1 m, 13.6 cm, and 96.1 m3/ha. Stemwood volume is ca 60% of total above ground biomass. Leaf biomass is important, the LAI being 7–8, good for shading out weeds. Average amount of dead litter is 4800 kg/ha. In Java, there may be 3 MT/ha leaves and 2 MT/ha twigs and branches beneath the trees (NAS, 1982a). On infertile abandoned sites in Papua, trees grew 6 m in 2 years, 17 m in 8 years. On shallow arid soils in West Bengal, yields were only 5m3/ha/yr at the 15th year. Under moister conditions 10 m3 is reported, 17–20 in Indonesia and Malaysia.

Energy

Wiersum and Ramlan report that yields can run higher than 20 m3/ha/yr on a 10–20 year rotation. On poor soils yields drop to 8–12 m3. On the Island of Madura, with annual rainfall 1700–1900 mm, 7–12 year old rotations run 7.6–9 m3/ha/yr, but on West Bengalese laterites with annual precipitation 1,000–14,000 mm, yields are only 2–6 m3/ha/yr in 10–20 year rotations. With its capacity to produce good fuelwood on poor soils, even where there are extended dry seasons, the species "merits large scale testing as a fuelwood species" (NAS, 1980). Wood has specific gravity of 0.6–0.75 and calorific value of 4,800–4,900 kcal/kg. Wood yields excellent charcoal that glows well and burns without smoke or sparks. Litter beneath the trees, both branches and dried leaves, annually adds up to 4.5–6 MT/ha, all used for fuel in China. Hawaiian grown material possesses N-fixing nodules.

Biotic Factors

While no pest or disease problems are reported in Indonesia, insects and nematodes have been reported to attack seedlings in Zanzibar. The rust Uromyces digitatus has been a problem in Java, where it is also occasionally infested with a rather inocuous black mildew, Meliola adenanphererae. In India, the root rots are Ganoderma lucidum and Ganoderma applanatum. Hypothenemus dimorphus has caused shoot fatality in Malaysia. The weevil Hypomeces squamosus can be a pest in India and Malaysia. Used to cultivate Kerria lacca in India. On Java, the ant Iridomyrmex rufoniger may protect the plant from some phytophagous insects.

References

Complete list of references for Duke, Handbook of Energy Crops
Last update Tuesday, January 6, 1998 by aw