Australasian tree forming large monospecific stands in swampy areas of southern Florida. The tree is compressing the distribution of a poorly-adapted swamp tree to wetter areas.
Evergreen tree to 20-25 m tall.
M. quinquenervia is one of a group of several closely related species. It has frequently been confused with M. viridiflora and intermediates between the two have been reported.
The tree reaches sexual maturity within two years. Spikes bear white malodorous flowers with large stamens. The flowers produce large quantities of pollen and nectar and are pollinated by bees. The fruit is a woody capsule (4 mm) containing many minute seeds (<1.5 mm, 30,000 seeds g-1). Seeds have no special buoyancy structures and are usually poorly dispersed but in hurricane winds seeds can spread up to 7 km. Seeds may be retained in the seed capsule for several years, with up to 20 million seeds stored per tree. They are generally released when flow of moisture from the tree to the capsule is interrupted by the death of the branch usually as a result of fire or frost. However, some continuous seedfall has been observed with seasonal peaks. In Florida 10-20% of released seeds germinate. Seedlings grow up to 2 m per year.
Resistant to wind, drought, fires and salt water. It has only slight resistance to frost although rootstock survives and sprouts. Coppices from cut stumps. The thick spongy bark of the trunk is fire proof but the outer layer highly flammable. The leaves and branches are killed during fires but are rapidly replaced by sprouts. Under flooded conditions fibrous roots are formed at the base of the trunk.
Species becomes locally dominant in swampy areas over a wide geographical area. It successfully competes with and outgrows other vegetation.
The wood is used for a number of purposes in Australia. It is suitable for windbreaks and beach planting. The papery bark is used as fruit packing material and torches.
Native to eastern Australia, Papua New Guinea and Irian Jaya and often forms pure stands. It is relatively common throughout its range. Formerly thought to occur in New Caledonia, where the tree is now considered to be a distinct species.
Grows at an altitude of 5 - 100 m. It has broad mean annual temperature (18° C to 34° C) and rainfall (1000 mm to 5000 mm) requirements. Climate is monsoonal in the tropical part of its distribution.
In Australia the tree is sometimes considered to be fire intolerant and natural stands, which are often pure, are confined to wetlands. It occurs most frequently on peaty humic gleys, sandy at the surface but with silt or clay below and with a high organic component.
Not reported in Australia.
In Australia insects significantly reduce girth, height and biomass increment in saplings.
Introduced to Florida as an ornamental in 1906 in at least two coastal locations. Seeding from airplanes was carried out in the 1930s and in the 1940s trees were planted inland. In Hawai'i over 1.7 million trees have been planted in forestry plots and species is now naturalized in undisturbed mesic forest (altitude 30-890 m). First cultivated in 1920 using seeds from Florida.
The seasonal water regime and frequency of fire are the major factors determining the suitability of sites for M. quinquenervia establishment. The rate of spread of the tree increased dramatically with increased fire regime and the creation of new invasion foci resulting from natural seed dispersal. For many years M. quinquenervia caused no problems in Florida.
Southern Florida consists of a large swampy lowland region where slight changes in elevation alter the water regime which affects drainage, fire and salinity. The climate is sub-tropical with an annual rainfall of 1600 mm falling mostly between May and October. Occasional frosts occur.
The slight difference in elevation and associated variation in water regime result in a number of vegetation types including mangroves, marshes and forests. The Florida vegetation is isolated from other sub-tropical regions of northern America and is rich in endemics but prone to invasions.
Free from insect herbivory.
M. quinquenervia displaces native vegetation particularly Taxodium distichum var. nutans, a temperate tree at the limit of its range. Its dense canopy casts deep shade, and in association with its likely allelopathic properties, restricts ground vegetation. It is poorly utilized by wildlife. By increasing the forest cover it could result in higher demand for ground water and lowering of the water-table.
Was considered to be a worthwhile and beneficial plant prior to its spread. Presently has no commercial uses but could be used for cellulose or as a fuel. As a nectar and pollen source it is important to the beekeeping industry. It appears to be a respiratory irritant when found close to human habitations and seems to repel mosquitos.
In Florida current management programmes include a mixture of manual, mechanical and herbicidal control. Biological control is under study and a number of insect species are being evaluated in Australia. Since fire frequency is determined by water regime and water regime can be altered in large areas of southern Florida, water management is a possible means of limiting the spread.
M. quinquenervia becomes dominant on the ecotone between dry pine forests and swamp forest where the conditions are either too wet for pine or too dry for Taxodium distichum var. nutans. There appear to be few fire-tolerant tree species particularly suited to the south Florida environment, including T. distichum which phenology is out of phase with the local environment.
It has been suggested that in Florida trees are quite different in appearance from those observed in Australia. They are generally taller, straighter and form very dense populations and grow much faster. This appears to result from the absence of herbivory. Differences in fire tolerance between Florida and Australia may also be attributable to differences in herbivory. Climatic conditions in Florida and in New South Wales, where the seed source originated, are similar.