Eucalyptus camaldulensis

Eucalyptus camaldulensis, commonly known as river red gum, is a flowering plant in the family Myrtaceae, and is endemic to Australia. It is a tree with smooth white or cream-coloured bark, lance-shaped or curved adult leaves, flower buds in groups of seven or nine, white flowers and hemispherical fruit with the valves extending beyond the rim. A familiar and iconic tree, it is seen along many watercourses across inland Australia, providing shade in the extreme temperatures of central Australia and elsewhere.

thumb|225px|Trunk and bark

thumb|Flower buds

thumb|225px|Flowers

thumb|225px|Fruit

Description

Eucalyptus camaldulensis is a tree that typically grows to a height of but sometimes to 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, long and wide. Adult leaves are lance-shaped to curved, the same dull green or greyish green colour on both sides, long and wide on a petiole long. The flower buds are arranged in groups of seven, nine or sometimes eleven, in leaf axils on a peduncle long, the individual flowers on pedicels long. Mature buds are oval to more or less spherical, green to creamy yellow, long and wide with a prominently beaked operculum long. Flowering mainly occurs in summer and the flowers are white. The fruit is a woody, hemispherical capsule long and wide on a pedicel long with the valves raised above the rim. The plant's flowers bloom for a long time throughout the year.

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.

Taxonomy and naming

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

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: has mature flower buds with a pointed operculum long and erect stamens and broadly lance-shaped or egg-shaped juvenile leaves;

Eucalyptus camaldulensis subsp. arida Ian Brooker & M.W.McDonald has bluish green adult leaves with only a few veins and mature flowers buds with a curved to rounded operculum long;
Eucalyptus camaldulensis Dehnh. subsp. camaldulensis 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 has mature flower buds that are small with a conical operculum long and broad juvenile leaves that are usually covered with a powdery bloom;
Eucalyptus camaldulensis subsp. obtusa (Blakely) Ian Brooker & M.W.McDonald has white, powdery bark in some months and mature flower buds with a curved, conical operculum long;
Eucalyptus camaldulensis subsp. refulgens Ian Brooker & M.W.McDonald has very glossy green adult leaves with a dense network of veins;
Eucalyptus camaldulensis subsp. simulata Ian Brooker & Kleinig. has a horn-shaped operculum 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. and was grown there for about one hundred years before being removed in the 1920s.

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). 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. Finally in 1934, William Blakely recognised Dehnhardt's priority and the name E. camaldulensis for river red gum was accepted.

Northern Territory Aboriginal names for this species are:

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).

is the name of this tree in the Miriwoong language of the Kimberley.

Distribution and habitat

thumb|upright|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.

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.
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.
Subspecies minima is endemic to South Australia, where it grows in the northern Flinders Ranges and the northern Eyre Peninsula.

Eucalyptus camaldulensis grows under a wide range of climatic conditions from tropical to temperate, but the main areas are characterised by 5 to 20 frosts in winter and high summer temperatures. Temperature conditions may vary from a minimum of -6°C to a maximum of 54°C with a diurnal range up to 21°C.

Ecology

thumb|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. 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.

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.

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. lists E. camaldulensis as a weed in Portugal, Canary Islands, South Africa, Spain, Bangladesh, the United States, Ecuador, the Galapagos and other countries.

Reproduction and dispersion

The flower begins as an "invaginated receptacle". The operculum, or cap, protects the interior of the flower bud, as the male and female parts develop.

The male parts of the flower consist of the stamen, a slender filament, and the anther, two pollen sacs located at the top of the stamen. The anther sacs open into longitudinal slits to release their pollen. These filaments will extend to encircle the receptacle during flowering.

The female parts of the flower, the ovaries, are contained in ovary chambers. These chambers are separated from the receptacle containing the male parts by a disc. From the top of the ovaries a structure called the style extends into the receptacle, to form the stigma.

During flowering, pollen from the anthers can fall onto the stigma. This can occasionally lead to self-pollination, although the stigma does not become receptive until a few days after the operculum has been detached by the expanding stamens, and the flower's pollen has already been released. Fertilisation will therefore occur with other flowers on the same tree or other flowers on a different tree. Insects, birds, and small mammals help in the pollination of other flowers. while natural flooding occurs during winter and spring. and is widely recognised due to its widespread range. The use of the waterways for seasonal recreation also occurs within the habitat of the river red gum, again due their fundamental link to watercourses and floodplains.

Population management

The predilection of the river red gum for waterways has been a successful evolutionary niche. This has resulted in a large population and range for the species, and so it is not considered endangered. Changes in its habitat, however, could be detrimental not just for the tree, but also for species that depend on the tree for their own survival. These changes include grazing, and water regulation for irrigation purposes. For example, grazing reduces the ability of the species to regenerate, as stock eat or trample the seedlings. However, grazing may aid regeneration by removing thick ground cover.

Cazneaux TreePhotographed by Harold Cazneaux in the Spirit of Endurance;
Separation TreeWhere celebrations were held when Victoria became a separate colony to New South Wales;
The Old Gum TreeWhere the colony of South Australia was proclaimed;
The Queen's TreePlanted in Kings Park, Perth Western Australia in 1954 by Queen Elizabeth II on her first visit to Australia.

Galleries

File:River Red Gum Bolin Bolin Billabong.JPG|A river red gum near Bolin Bolin Billabong on the Yarra River.

File:Murray River redgums at Echuca.jpg|A view down the Murray River every tree pictured is a river red gum.

File:700 yr red river gum02.jpg|A 700-year-old tree at the Wonga Wetlands, NSW.

File:Barcoo river, Tambo.JPG|Many river red gums on the banks of the Barcoo River, south-west Queensland.

File:Eucalyptus camaldulensis DSC 5750 (29086898504).jpg|River red gums; the Murrumbidgee River in flood.

File:CSIRO ScienceImage 4682 Casneauxs Tree with the ramparts of Wilpena Pound in the background Flinders Ranges SA 1992.jpg|The Cazneaux Tree, near Wilpena Pound in Flinders Ranges National Park.

File:Eucalyptus camaldulensis - Queen's Tree - Kings Park.jpg|"The Queen's Tree", Kings Park, Perth, WA.

File:RiverRedGum_Hay_NSW.jpg|A river red gum in a bend of the Murrumbidgee River near Hay, NSW.

File:Grampians NP Chatauqua Peak Walk Eucalyptus camaldulensis.jpg|In Grampians National Park, Victoria.

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References

General references

CSIRO, 2004. Eucalyptus camaldulensis Dehnh. River Red Gum. [https://web.archive.org/web/20060815035031/http://www.cmis.csiro.au/healthycountry/CCScience/TB/eucalyptus-camaldulensis/index.html]
Mackay, Norman and David Eastburn (eds) 1990. The Murray. Murray-Darling Basin Commission, Canberra. .

External links

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