| Black wattle | |
|---|---|
 | |
| OnMaui | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Rosids |
| Order: | Fabales |
| Family: | Fabaceae |
| Subfamily: | Caesalpinioideae |
| Clade: | Mimosoid clade |
| Genus: | Acacia |
| Species: | A. mearnsii |
| Binomial name | |
| Acacia mearnsii | |
 | |
| Occurrence data fromAVH | |
| Synonyms[1] | |
| |
Acacia mearnsii, commonly known asblack wattle,late black wattle orgreen wattle,[2] is a species of flowering plant in the familyFabaceae and isendemic to south-eastern Australia. It is usually an erect tree with smooth bark,bipinnate leaves and spherical heads of fragrant pale yellow or cream-coloured flowers followed by black to reddish brownpods. In some other parts of the world, it is regarded as aninvasive species.
Acacis mearnsii is a spreading shrub or erect tree that typically grows to a height of 10 m (33 ft) and has smooth bark, sometimes corrugated at the base of old specimens. The leaves are bipinnate with 7 to 31 pairs ofpinnae, each with 25 to 78 pairs ofpinnules. There is a sphericalgland up to 8 mm (0.31 in) below the lowest pair of pinnae. The scented flowers are arranged in spherical heads of 20 to 40, pale yellow or cream-coloured, with the heads on hairypeduncles 2–8 mm (0.08–0.31 in) long. Flowering mainly occurs from October to December and black to reddish-brown pods, 30–150 mm (1.2–5.9 in) long and 4.5–8 mm (0.18–0.31 in) wide develop from October to February.[2][3][4]
Belgian naturalistÉmile Auguste Joseph De Wildeman described the black wattle in 1925 in his bookPlantae Bequaertianae.[5] The species is named after American naturalistEdgar Alexander Mearns, who collected the type from a cultivated specimen in EastAfrica.[6] Along with other bipinnate wattles, it is classified in the sectionBotrycephalae within the subgenusPhyllodineae in the genusAcacia. An analysis of genomic and chloroplast DNA along with morphological characters found that the section is polyphyletic, though the close relationships of many species were unable to be resolved.Acacia mearnsii appears to be most closely related toA. dealbata,A. nanodealbata andA. baileyana.[7]
A. mearnsii is native to south-easternAustralia andTasmania, but has been introduced toNorth America,South America,Asia,Europe,Pacific andIndian Ocean islands,Africa, andNew Zealand.[8][9][10][11][12] In these areas it is often used as a commercial source oftannin or a source of firewood for local communities.
In some regions, introduced plants of this species are considered a weed. This is because they threaten nativehabitats by competing with indigenous vegetation, replacing grass communities, reducing nativebiodiversity and increasing water loss fromriparian zones. In Africa,A. mearnsii competes with local vegetation for nitrogen and water resources, which are particularly scarce in certain regions, endangering the livelihoods of millions of people.[13]
In its native rangeA. mearnsii is a tree of tall woodland and forests in subtropical and warm temperate regions. In Africa the species grows in disturbed areas, range/grasslands, riparian zones, urban areas, water courses, andmesic habitats at an altitude of between 600 and 1,700 metres (2,000 and 5,600 ft). In Africa it grows in a range ofclimates including warm temperate dry climates and moist tropical climates.A. mearnsii is reported to tolerate an annualprecipitation of between 66 and 228 cm (26 and 90 in), an annual mean temperature of 14.7 to 27.8 °C (58.5 to 82.0 °F), and a pH of 5.0–7.2.[14]A. mearnsii does not grow well on very dry and poor soils.[15]
A. mearnsii plays an important role in the native ecosystem of Australia. As apioneer plant it quickly binds theerosion-prone soil following thebushfires that are common in its Australian habitats. Like otherleguminous plants, itfixes atmospheric nitrogen in the soil. Other woodland species can rapidly use these increased nitrogen levels provided by the nodules of bacteria present in their expansive root systems. Hence they play a critical part in the natural regeneration of Australian bushland after fires.
Mycorrhizal fungi attach to the roots to produce food formarsupial animals, and these animals in turn disperse the spores in their droppings to perpetuate the symbiotic relationship between the wattle's roots and mycorrhizal fungi.
The cracks and crevices in the wattle's bark are home for many insects and invertebrates. The rareTasmanian hairstreak butterfly lays her eggs in these cracks, which hatch to produce caterpillar larva attended by ants (Iridomyrmex sp.) that feed off the sweet exudates from the larva.[citation needed]A. mearnsii is used similarly as a larval host plant and food source by the imperial hairstreak,Jalmenus evagoras.[20]
The tree is home to various grubs, such as wood moths, which provide a food source to black cockatoos, which strip the bark for access to these borers.
During winter insects, birds and marsupials are hosted by the black wattle with the aid of their supplies ofnectar in their leaf axials. These creatures provide an important predatory role to deal with tree dieback caused by scarab beetles and pasture pests.
Black wattles, along with gums, native box and native hop form the framework vegetation on so-called "hill-topping" sites. They are often constitute isolated remnant pockets of native vegetation amongst a lower sea of exotic pasture. These "hill-topping" sites are critical habitat for male butterflies to attract females for mating, which then lay their eggs under the wattle's bark elsewhere but still within close proximity. It's the only acceptable mating site in the area for these butterflies.
Black wattle flowers provide verynitrogen-rich pollen with no nectar. They attract pollen-feeding birds, such aswattlebirds,yellow-throated honeyeaters andNew Holland honeyeaters. The protein-rich nectar in the leaf axials is very sustaining for nurturing the growth of juvenile nestlings and young invertebrates, e.g. ants.
Ants harvest the seed, attracted by the fleshy, oil-richelaiosome (or seed stalk), which they bury and store in widely dispersed locations. These seeds are buried ready for germinating with the next soaking rains. However, a "wattle seed-eating insect" which enjoys liquid meals using its proboscis-like injector to pierce thetesta and suck out the embryo, often reduces the seed's viability.[21]
In some parts of the world,A. mearnsii is considered to be an invasive species. Its invasiveness is due to its production of large numbers of seeds each year and to its largecrown that shades other species.[22]
InSouth Africa it is listed as a Category 2 invader in the National Environmental Biodiversity Management Act. This means a permit is required to handle a species and ensure it does not spread beyond the area of the permit.[23]
TheNgunnawal people of theAustralian Capital Territory use the gum as food and to make cement (when mixed with ash), and to ensure a supply of sap, the bark was cut in the autumn.[24] The bark was also used to make coarse rope and string, and used to be infused in water to make a medicine for indigestion.[24]
A. mearnsii produces copious numbers of small seeds that are not dispersed actively. The species may resprout from basal shoots following a fire.[8] It also generates numerous suckers that result in thickets consisting of clones.[8] Seeds may remain viable for up to 50 years.[25]
Leuco-fisetinidin, a flavan-3,4-diol (leucoanthocyanidin) and a monomer of the condensed tannins calledprofisetinidins, can be extracted from the heartwood ofA. mearnsii.[26]
{{cite book}}: CS1 maint: others (link){{cite web}}:|archive-url= is malformed: timestamp (help)CS1 maint: url-status (link)
Authority control databases: National |
|---|