Melaleuca forests and woodlands

The bioregion supports a large number of Melaleuca

formations ranging from tall open forests to sparse

shrublands. The genus displays a broad range of edaphic

tolerances, with the majority of species being well

adapted to soils with impeded drainage.

Associations dominated by Melaleuca leucadendra,Melaleuca dealbata and Melaleuca fluviatilis (to a lesserextent) in moist to very wet coastal lowland situationsrepresent the optimal structural development in the WetTropics. Associations formed by the two former speciesoccur in a range of landscape positions including riparianfringes, swampy alluvial flats, dune swales and broaderloamy coastal alluvial plains. These often tall open forestcommunities can vary considerably in the composition oftheir lower strata, ranging from extremely sparse shruband ground covers in swampy dune swales to welldeveloped scrub in habitats formed on well drained, loamysoils. Melaleuca fluviatilis is restricted to well drained,riparian levees on major streams where it mixes with arange of rainforest and sclerophyll species.

Melaleuca quinquenervia has a wide range of edaphictolerances. Structural and floristic variability within thealliance is often a response to variations in geologicalsubstrate and soil drainage. Representative associationsoccur in a range of landscape positions although itsmaximum development is as an open forest associatedwith permanently wet swamps on the coastal lowlands. Arestricted alliance dominated by Melaleuca cajuputi openforest (51a) occupies a similar ecological niche, which cancause some confusion in terms of species identification insome locations. Lesser developed Melaleucaquinquenervia associations occur on prograding coastaldune systems (with shallow organic hardpan layers), onmetamorphic footslopes (quartzites) and on brackish soilswhere the species mixes with a range of salt tolerantsedges and forbs.

Melaleuca viridiflora dominated alliances are found in arange of topographic positions with variations controlledlargely by soil physical properties. Minor variations in soildrainage are a particularly important regulator ofvegetation structure and floristics. On poorly drainedalluvial flats, (extensive in the southern coastal portions ofthe bioregion), Melaleuca viridiflora dominates shrublandcommunities (association 59a), mixing with Lophostemonsuaveolens (association 59d) and a range of eucalyptspecies (Association 59b) as soil drainage improves. Landmanagement history plays a major role in determiningvegetation structure given a long period in the absence offire, species including Allocasuarina littoralis and Grevillea

pteridifolia may become locally abundant or even becomeco-dominant species. The alliance also includes a numberof unusual variations including an association with Banksiarobur (59c) and a mixed shrubland variation whichoccupies metamorphic hillslopes in upland areas to thewest of Kuranda (59f).

The remaining alliances within this formation are highlyrestricted in the Wet Tropics, being more typical of theCape York Peninsula bioregion. These include lowMelaleuca argentea forests along swampy drainage lines(50a) and low mixed swamp forest with Melaleuca saligna(57a). These species occupy similar niches to Melaleucaquinquenervia; however they may displace this species inthe far northern coastal portions of the bioregion.Melaleuca foliolosa forms a low shrubland on the marginsof saline flats near the Annan River in the far north of thebioregion. Melaleuca stenostachya shrubland (Association58a) occupies areas of infertile, poorly drained alluvialwash to the west of Mt Molloy, representing perhaps themost adverse habitat conditions within the bioregion forthe Melaleuca formation.

Facts and figures

Vegetation alliances

Melaleuca argentea forests andwoodlandsMelaleuca cajuputi woodlandsMelaleuca dealbata forests andwoodlandsMelaleuca fluviatilis forests andwoodlandsMelaleuca foliolosa forests andwoodlandsMelaleuca leucadendra forests andwoodlandsMelaleuca quinquenervia forestsand woodlandsMelaleuca saligna forests andwoodlandsMelaleuca stenostachya forests andwoodlandsMelaleuca viridiflora forests andwoodlands

Current extent in the

bioregion 42,946haArea protected 12,217ha (28%)

SCLEROPHYLL FORESTS AND WOODLANDS

OF THE WET TROPICS BIOREGIONMelaleuca forests and woodlands (vegetation codes 50a-59g)

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Geography

Melaleuca forests and woodlands are extensive, occupyingsignificant portions of the landscape across a range oftopographic and climatic zones. The most extensiveremaining occurrences are associated with poorly drainedalluvial flats on the coastal plain south of Cardwell. Swampforests formed by alliances of Melaleuca quinquenervia,Melaleuca cajuputi, Melaleuca leucadendra and Melaleucadealbata are relatively extensive on the very wet portions ofthe coastal plain from Ingham northwards to CapeTribulation. A rare highland example of Melaleucaquinquenervia swampland is also found in theKoombooloomba area.

Drier Melaleuca associations are common on the westernmargins of the bioregion with mixed shrublandassociations formed by Melaleuca viridiflora and Melaleucastenostachya common on metamorphic hillslopes and siltyoutwash plains between Myola (Kuranda map sheet) andMt Carbine (Rumula map sheet).

Impacts and changes

Melaleuca quinquenervia forest dominated the coastallowlands in what was known as the Babinda Swamp. Noremnants of this swamp now remain and the area isoccupied by an extensive drainage system. Large areas ofpeaty soil within this former swamp have proved totallyunsuitable for sugar cane cultivation and remainessentially as wastelands. Changes to the structure ofMelaleuca quinquenervia dominated communities mayoccur over time as a result of intense fire events whichresult in the reduction of previously tall open forest areasto whipstick shrubland. These whipstick shrublands formextremely dense stands of thin-stemmed melaleucas up toseveral metres high, often interspersed amongst tall forestor woodland.

Key values

• Seasonal wetland habitat for a range of fauna species

• Major seasonal resource for nomadic nectar seekingbirds and mammals

• Swampland habitats have an important hydrologicalfunction. These habitats provide an important source ofnutrient that is exchanged during period of overbankflow. Also provide pathways for overbank flow duringflood events

• Melaleuca viridiflora communities host a number of rareand threatened plant species including Calochiluspsednus, Genoplesium tectum, Eulophia bicallosa,Pachystoma pubescens, and Myrmecodia beccarii.

Threatening processes

• Alteration to floodplain hydrology including constructionof drains

• Land clearing and reclamation

• Altered fire regimes

• Fragmentation of habitat and invasion by exotic shrub,grass and herb species.

Tenure

Represented within reserve system, including: NgalbaBulal NP, Daintree NP, Girramay NP, Girringun NP, HalifaxBay Wetlands NP, Hinchinbrook Island NP, Hull River NP,Kuranda NP, Maria Creek NP, Mount Mackay NP, MowbrayNP, Paluma Range NP, Russell River NP, Djiru NP andOrpheus Island NP.

Management considerations

• Appropriate fire management and prescribed burning isimportant for the maintenance and dynamics of thisextensive formation

• Control of Pond Apple (Annona glabra) in wetlandhabitats

• Return of natural hydrological regimes to swamplandcommunities affected by drainage

• Invasion and replacement of groundcovers by exoticgrass and herb species.