The paperbark is a very successful tree in temperate eastern Australia. In pre-European times it formed vast forests on coastal swampy land. It replaces eucalypts on seasonally-inundated alluvial soil, forming monotypic forests or woodlands. It also grows within swamps and along the banks of streams in the lower reaches of catchments.
Paperbark forests are not a diverse habitat. Often there are no other tree species present. Where the ground is slightly elevated, eucalypts grow as emergents, especially the forest red gum (Eucalyptus tereticornis), and also the swamp mahogany (Lophostemon suaveolens). Where the soil becomes saline, paperbarks are replaced by swamp oak (Casuarina glauca).
In paperbark forests, the ground cover is usually blady grass (Imperata cylindrica). This grass is very widely distributed in Australia, Asia, and Africa, and it has spread to the United States to become a serious weed. Very few shrubs grow within paperbark forests, and only one vine is common, strawpod (Parsonia straminea).
The fauna of paperbark forests is limited. Frogs are usually well-represented by about 8-12 species, and these are preyed upon by the keelback (Tropidonophis mairii), a harmless colubrid snake sometimes found in large numbers. Kangaroos and wallabies are largely confined to areas supporting blady grass (Imperata cylindrica), or other palatable species. Paperbarks do not develop hollow limbs so they do not provide shelter for possums, gliders, parrots, and other hole-nesting birds. These species will occur where emergent eucalypts are present, but a monotypic stand of paperbarks is very poor habitat for mammals and most birds.
Paperbarks flower prolifically and the blossoms attract large numbers of nectar-feeding birds and bats. The birds include several species of honey eater and lorikeet, and there are four species of temperate nectar-feeding bat, ranging in weight from 15 grams up to a kilogram. When a paperbark forest is in bloom, it becomes very noisy, with squawking birds by day, and squabbling bats by night. Feral and domesticated honeybees take much of the honey and nectar. Most of the coastal paperbark forests were cleared in the past for pasture. The remaining stands are threatened by real estate development. In Brisbane, Australia's third largest city, the conservation of remaining paperbarks has become a conservation issue. The Brisbane City Council opposed development of one paperbark stand as a shopping centre, and the site has now become a bushland park called Deagon Wetlands.
In a recent book, Wild Places of Greater Brisbane (1996), Brisbane City Council Officer Stephen Poole had this to say about Deagon: "Paperbark forest has the highest loss rate and is under the most threat of any vegetation type in South-East Queensland. This, and its relatively undisturbed nature, make the Deagon Wetlands one of the most important bushland sites within the metropolitan area. The wetlands are administered by Brisbane City Council as a Conservation Reserve, specifically established to protect this fast disappearing habitat."
Paperbarks germinate prolifically and grow quickly, and when given the chance, they soon reclaim cleared swampy ground. The species remains very common on disturbed swampy land despite the broad-scale clearing of the past. It is the habitat type that is under threat, not the species.
Paperbark remnants are very prone to weed invasion. On one side of the Deagen Wetlands, adjacent to housing, a wide range of garden plants is invading the forest, by courtesy of garden dumping. The worst invader is probably groundsel bush (Baccharis halimifolia), a declared noxious weed originally introduced from North America as an ornamental. Another weed is broad-leaved pepper tree (Schinus terebinthifolius), which forms a tall shrub layer along swampy watercourses. This shrub or small tree is widely grown as an ornamental, and its spread as a weed appears to be relatively recent. I have seen lorikeets eating the fruits and birds are apparently spreading the seeds. Another invasive weed is morning glory (Ipomoea indica).
I am aware that Australian insects have been introduced to Florida in a bid to control the spread of melaleuca. I would question whether this is likely to succeed. Melaleucas in Australia are attacked by a very large number of insects yet they still grow naturally in vast monocultures, representing one of the most common trees in the region. In pre-European times it was almost certainly the most common tree along the coastal strip of southern Queensland and northern New South Wales. From the few pictures I have seen, the paperbark forests of Florida look much like the paperbark forests here. However, in Australia, the insect predators are heavily controlled by parasites, and perhaps by birds. For example, the larvae and eggs of the pergid sawfly (Lophyrotoma zonalis) which is being studied for possible introduction into Florida, are heavily parasitised in Australia. One can only hope that in Florida, free from their controlling agents in Australia, the insects will be dramatically successful in controlling Melaleuca.
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