Eucalyptus camaldulensis

Eucalyptus camaldulensis is a tree that typically grows to a height of 20 metres (66 ft) but sometimes to 45 metres (148 ft) and often does not develop a lignotuber. The bark is smooth white or cream-coloured with patches of yellow, pink or brown. There are often loose, rough slabs of bark near the base. The juvenile leaves are lance-shaped, 80–180 mm (3.1–7.1 in) long and 13–25 mm (0.51–0.98 in) wide. Adult leaves are lance-shaped to curved, the same dull green or greyish green colour on both sides, 50–300 mm (2.0–11.8 in) long and 7–32 mm (0.28–1.26 in) wide on a petiole 8–33 mm (0.31–1.30 in) long. The flower buds are arranged in groups of seven, nine or sometimes eleven, in leaf axils on a peduncle 5–28 mm (0.20–1.10 in) long, the individual flowers on pedicels 2–10 mm (0.079–0.394 in) long. Mature buds are oval to more or less spherical, green to creamy yellow, 6–9 mm (0.24–0.35 in) long and 4–6 mm (0.16–0.24 in) wide with a prominently beaked operculum 3–7 mm (0.12–0.28 in) long. Flowering mainly occurs in summer and the flowers are white. The fruit is a woody, hemispherical capsule 2–5 mm (0.079–0.197 in) long and 4–10 mm (0.16–0.39 in) wide on a pedicel 3–12 mm (0.12–0.47 in) long with the valves raised above the rim.[3][4][5][6][7]

The limbs of river red gums, sometimes whole trees, often fall without warning so that camping or picnicking near them is dangerous, especially if a tree has dead limbs or the tree is under stress.[8]

Eucalyptus camaldulensis was first formally described in 1832 by Friedrich Dehnhardt who published the description in Catalogus Plantarum Horti Camaldulensis.[9][10]

Seven subspecies of E. camaldulensis have been described and accepted by the Australian Plant Census. The most variable character is the shape and size of the operculum, followed by the arrangement of the stamens in the mature buds and the density of veins visible in the leaves. The subspecies are:[4]

• Eucalyptus camaldulensis subsp. acuta Ian Brooker & M.W.McDonald[11] has mature flower buds with a pointed operculum 6–9 mm (0.24–0.35 in) long and erect stamens and broadly lance-shaped or egg-shaped juvenile leaves;
• Eucalyptus camaldulensis subsp. arida Ian Brooker & M.W.McDonald[12] has bluish green adult leaves with only a few veins and mature flowers buds with a curved to rounded operculum 3–7 mm (0.12–0.28 in) long;
• Eucalyptus camaldulensis Dehnh. subsp. camaldulensis[13] has a strongly beaked operculum, incurved or irregularly bent stamens and narrow lance-shaped juvenile leaves;
• Eucalyptus camaldulensis subsp. minima Ian Brooker & M.W.McDonald[14] has mature flower buds that are small with a conical operculum 2–4 mm (0.079–0.157 in) long and broad juvenile leaves that are usually covered with a powdery bloom;
• Eucalyptus camaldulensis subsp. obtusa (Blakely) Ian Brooker & M.W.McDonald[15] has white, powdery bark in some months and mature flower buds with a curved, conical operculum 4–7 mm (0.16–0.28 in) long;
• Eucalyptus camaldulensis subsp. refulgens Ian Brooker & M.W.McDonald[16] has very glossy green adult leaves with a dense network of veins;
• Eucalyptus camaldulensis subsp. simulata Ian Brooker & Kleinig.[17] has a horn-shaped operculum 9–16 mm (0.35–0.63 in) long.

The specific epithet (camaldulensis) is a reference to a private estate garden (L'Hortus Camaldulensis di Napoli) near the Camaldoli monastery in Naples, where Frederick Dehnhardt was the chief gardener.[4] The type specimen was grown in the gardens from seed presumably collected in 1817 near Condobolin by Allan Cunningham,[18] and was grown there for about one hundred years before being removed in the 1920s.[19] Herbarium specimen of the holotype is deposited in the herbarium of Natural History Museum of Vienna.[20]

Although Dehnhardt was the first to formally describe E. camaldulensis, his book was largely unknown to the botanical community. In 1847 Diederich von Schlechtendal gave the species the name Eucalyptus rostrata but the name was illegitimate (a nomen illegitimum) because it had already been applied by Cavanilles to a different species (now known as Eucalyptus robusta).[21] In the 1850s, Ferdinand von Mueller labelled some specimens of river red gum as Eucalyptus longirostris and in 1856 Friedrich Miquel published a description of von Mueller's specimens, formalising the name E. longirostris.[22] Finally in 1934, William Blakely recognised Dehnhardt's priority and the name E. camaldulensis for river red gum was accepted.[19]

Northern Territory Aboriginal names for this species are:[23]

• aper (Alyawarr, Anmatyerr), aper or per (Eastern Arrernte), apere (Kaytetye), aylpele (Pintupi Luritja), itara, ngapiri, pipalya, yitara (Pitjantjatjara) apara, itara, piipalya, (Waramangu), kunjumarra (Warlpiri), kunjumarra and ngapiri (Western Arrernte).

Dimilan is the name of this tree in the Miriwoong language of the Kimberley.[24]

The dry river beds of central Australia have sufficient underground water flow to sustain the trees.

Eucalyptus camaldulensis has the widest natural distribution of any eucalyptus species. It is commonly found along waterways and there are only a few locations where the species is found away from a watercourse.[25][26]

• Subspecies acuta is common along rivers from south of Cape York Peninsula in Queensland to the north west slopes and plains of New South Wales but is absent from coastal areas and the arid inland.
• Subspecies arida has the widest distribution of the subspecies and is found in all mainland states except Victoria. It grows in arid regions but only where there is sufficient subsoil moisture.[4][27]
• Subspecies camaldulensis is the dominant eucalypt along the Murray-Darling river system and its tributaries. It also occurs on the Eyre and Yorke Peninsulas and Kangaroo Island in South Australia and in some locations along the Hunter River in New South Wales. It is the only subspecies in coastal Victoria.[4][28]
• Subspecies minima is endemic to South Australia, where it grows in the northern Flinders Ranges and the northern Eyre Peninsula.[4]
• Subspecies obtusa is endemic to tropical northern Australia, including parts of the Kimberley, the Top End and the Gulf of Carpentaria hinterland as far east as the Gilbert River, Queensland in Queensland.[4]
• Subspecies refulgens is endemic to the Pilbara-Gascoyne-Carnarvon region, along rivers flowing westwards, including along some of the tributaries of the upper Murchison River.[4]
• Subspecies simulata is mainly restricted to some rivers on Cape York Peninsula, but with some populations further south.[4]

Eucalyptus camaldulensis, Edward River, NSW

The species can be found along the banks of watercourses, as well as the floodplains of those watercourses. Due to the proximity to these watercourses, river red gum is subject to regular flooding in its natural habitat. River red gum prefers soils with clay content. The trees not only rely on rainfall but also on regular flooding, since flooding recharges the sub-soil with water.[29]

The association of the river red gum with water makes the tree a natural habitat choice, indeed sometimes the only choice in drier areas, for other species. The trees provide a breeding habitat for fish during the flooding season, which also benefits aquatic bird life that depend on fish as a food source during their own breeding season. Wilson,[26] who examined the management of river red gums in NSW, suggests shelter is provided for fish in rivers and streams by fallen branches from the river red gum. The "snags" formed when river red gums fall into rivers such as the Glenelg, are an important part of river ecosystems, and vital habitat and breeding sites for native fish like river blackfish. Unfortunately most snags have been removed from these rivers, beginning in the 1850s, due to river-improvement strategies designed to prevent hazards to navigation, reduce damage to in-stream structures, rejuvenate or scour channels, and increase hydraulic capacity to reduce flooding.[30] However, the Murray–Darling Basin Commission has recognised the importance of snags as aquatic habitat, and a moratorium on their removal from the Murray River has been recommended.[31]

Hollows start to form at around 120–180 years of age, creating habitat for many wildlife species, including a range of breeding and roosting animals such as bats, carpet pythons, and birds.[26] The dense foliage of the tree also provides shade and shelter from the sun in drier areas.

The superb parrot, a threatened species, is amongst the bird species that nest in the river red gum.[32]

River red gums contribute to the provision of nutrients and energy for other species through leaf and insect fall. This is especially important to the ecology in areas of low nutrients.[26] The tree's preferred habitat of floodplains and watercourses also gives it the role of flood mitigator, which slows silt runoff.

The formation of the noted Barmah red gum forests is due to a relatively recent geological event in the Murray-Darling Basin involving the Cadell Fault.

River red gum seeds germinate readily after floods and require regular spring floods throughout their life to survive. In the Murray-Darling Basin, such floods are now rare due to river regulation for irrigation, and as a result, 75% of River red gums in the lower Murray are stressed, dead or dying.

The largest remaining stand of river red gum is the 65,000 ha (160,000 acres) Barmah-Millewa forest straddling the border of Victoria and New South Wales, due north of Melbourne. It retains enormous cultural significance to the Indigenous traditional owners, the Yorta Yorta Nation. Like many stands of river red gum, the Barmah-Millewa has been drastically altered by over 100 years of timber harvesting. There is a paucity of old hollow-bearing trees which provide habitat for rare and threatened fauna such as the superb parrot, brush-tailed phascogale and inland carpet python. (Though these species are currently not under threat.) The increasing scale of logging machinery is creating large areas of intensive soil disturbance and bare earth, which is likely to increase weed invasion and increase the likelihood of the extinction of rare understorey plants.

About 25,000 years ago, displacement occurred along the Cadell fault, raising the eastern edge of the fault (which runs north-south) 8–12 metres (26–39 ft) above the floodplain. This created a complex series of events. A section of the original Murray River channel immediately behind the fault was abandoned, and exists today as an empty channel known as Green Gully. The Goulburn River was dammed by the southern end of the fault to create a natural lake. The Murray River flowed to the north around the Cadell Fault, creating the channel of the Edward River which exists today and through which much of the Murray River's waters still flow. Then the natural dam on the Goulburn River failed, the lake drained, and the Murray River abruptly deviated to the south and started to flow through the smaller Goulburn River channel, creating "The Barmah Choke" and "The Narrows" (where the river channel is unusually narrow), before entering into the proper Murray River channel again.

The primary result of the Cadell Fault however is that the west-flowing water of the Murray River strikes the north-south running fault and diverts both north and south around the fault in the two main channels (Edwards and ancestral Goulburn) as well as a fan of small streams, and regularly floods a large amount of low-lying country in the area. These conditions are perfect for river red gums, which rapidly formed forests in the area. Thus the displacement of the Cadell Fault 25,000 years BP led directly to the formation of the Barmah river red gum forests.

Placard for "The Queen's Tree", Kings Park, Perth, WA

Examples of river red gums include:

• The Big Tree near Moulamein - one of the largest river red gums in the Riverina, with a circumference of 11.6 metres;[40]
• Cazneaux Tree - Photographed by Harold Cazneaux in the Spirit of Endurance;
• Separation Tree - Where celebrations were held when Victoria became a separate colony to New South Wales;
• The Old Gum Tree - Where the colony of South Australia was proclaimed;
• The Queen's Tree - Planted in Kings Park, Perth Western Australia in 1954 by Her Majesty Queen Elizabeth II on her first visit to Australia.

• Examples of river red gums
• 
  A river red gum near Bolin Bolin Billabong on the Yarra River.
• 
  A view down the Murray River – every tree pictured is a river red gum.
• 
  A 700-year-old tree at the Wonga Wetlands, NSW.
• 
  Many river red gums on the banks of the Barcoo River, south-west Queensland.
• 
  River red gums; the Murrumbidgee River in flood.
• 
  The Cazneaux Tree, near Wilpena Pound in Flinders Ranges National Park.
• 
  "The Queen's Tree", Kings Park, Perth, WA.
• 
  A river red gum in a bend of the Murrumbidgee River near Hay, NSW.

• List of Eucalyptus species
• List of named Eucalyptus trees
• Mountain ash
• Alpine ash
• Snow gum
• Barmah National Park

• CSIRO, 2004. Eucalyptus camaldulensis Dehnh. River Red Gum.
• Mackay, Norman and David Eastburn (eds) 1990. The Murray. Murray-Darling Basin Commission, Canberra. ISBN 1-875209-05-0.

Wikimedia Commons has media related to Eucalyptus camaldulensis.

Wikispecies has information related to Eucalyptus camaldulensis.

• Atlas of Living Australia: Eucalyptus camaldulensis
• Center for New Crops & Plant Products, Purdue University
• Invasive species compendium: Eucalyptus camaldulensis