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Magnoliopsida
Melaleuca Linnaeus, 1767
EOL Text
Depth range based on 4 specimens in 1 taxon.
Environmental ranges
Depth range (m): 1 - 1
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Source | http://www.iobis.org/mapper/?taxon_id=817036 |
Barcode of Life Data Systems (BOLD) Stats
Specimen Records:82
Specimens with Sequences:77
Specimens with Barcodes:25
Species:24
Species With Barcodes:22
Public Records:56
Public Species:13
Public BINs:0
Melaleuca /ˌmɛləˈljuːkə/ is a genus of plants in the myrtle family Myrtaceae. There are well over 200 recognised species, most of which are endemic to Australia.[2] A few species occur in Malesia and 7 species are endemic to New Caledonia.[2][3]
Contents
Setting[edit]
The species are shrubs and trees growing (depending on species) to 2–30 m (6.6–98.4 ft) tall, often with flaky, exfoliating bark. The leaves are evergreen, alternately arranged, ovate to lanceolate, 1–25 cm (0.39–9.84 in) long and 0.5–7 cm (0.20–2.76 in) broad, with an entire margin, dark green to grey-green in colour. The flowers are produced in dense clusters along the stems, each flower with fine small petals and a tight bundle of stamens; flower colour varies from white to pink, red, pale yellow or greenish. The fruit is a small capsule containing numerous minute seeds.
Melaleuca is closely related to the genus Callistemon; the main difference between the two is that the stamens are generally free in Callistemon but grouped into bundles in Melaleuca. Callistemon was recently placed into Melaleuca.[4]
In the wild, Melaleuca plants are generally found in open forest, woodland or shrubland, particularly along watercourses and the edges of swamps.
The best-accepted common name for Melaleuca is simply melaleuca; however most of the larger species are also known as tea tree,[citation needed] and the smaller types as honey myrtles,[citation needed] while those species in which the bark is shed in flat, flexible sheets are referred to as paperbarks.[citation needed] The Tea tree is presumably named for the brown colouration of many water courses caused by leaves shed from trees of this and similar species (for a famous example see Brown Lake (Stradbroke Island)). The name "tea tree" is also used for species in a related genus, Leptospermum, also in Myrtaceae.
One well-known melaleuca, M. alternifolia, is notable for its essential oil which is both anti-fungal and antibiotic,[citation needed] while safely usable for topical applications. This is produced on a commercial scale and marketed as Tea Tree Oil.
In Australia, Melaleuca species are used as food plants by the larvae of hepialid moths of the genus Aenetus including A. ligniveren. These burrow horizontally into the trunk, then vertically down.
Melaleucas are popular garden plants, both in Australia and other tropical areas worldwide. In Hawaii and the Florida Everglades, M. quinquenervia (Broad-leaved Paperbark) was introduced to help drain low-lying swampy areas. It has since gone on to become a serious invasive species with potentially very serious consequences because the plants are highly flammable and spread aggressively. Melaleuca populations have nearly quadrupled in southern Florida over the past decade, as can be noted on IFAS's SRFer Mapserver[5]
Uses[edit]
Traditional Aboriginal uses[edit]
Australian Aborigines have used the leaves for many medicinal purposes, including chewing the young leaves to alleviate headache and for other ailments.
Modern uses[edit]
Scientific studies have shown that tea tree oil made from M. alternifolia may have some promise for mild cases of acne and athlete's foot, however there are many health claims made for it that are not backed by medical evidence.
The oils of Melaleuca can be found in organic solutions of medication that claim to eliminate warts, including the human papillomavirus (HPV). No scientific evidence proves these claims.[6]
Melaleuca oils are the active ingredient in Burn-Aid, a popular minor burn first aid treatment.[7]
M. leucadendra oil, cajeput tree, is also used in many pet fish remedies such as Melafix and Bettafix to treat bacterial and fungal infections. Bettafix is a lighter dilution of cajeput tree oil, while Melafix is a stronger dilution. It is most commonly used to promote fin and tissue regrowth. The remedies are often associated with Betta fish (Siamese Fighting Fish) but are also used with other fish.
Invasive species in Florida[edit]
The species M. quinquenervia was introduced to Florida in the United States in the mid-1880s to assist in drying out swampy land and as a garden plant. It formed dense thickets and displaced native vegetation on 391,000 acres (1,580 km2) of wet pine flatwoods, sawgrass marshes, and cypress swamps in the southern part of the state. It is prohibited by DEP and listed as a noxious weed by FDACS.[8]
As an invasive species, M. quinquenervia raised serious environmental issues in Florida's Everglades and damaged the surrounding economy. Agricultural Research Service (ARS) scientists[9] from the Australian Biological Control Laboratory[10] suggested releasing biological controls in the form of insects that feed on this species.[11] In 1997 a weevil (Oxyops vitiosa) was released. It feeds on leaves and flower buds. The University of Florida reports that seed production has been reduced by about 50 percent "on trees they attack." Boreioglycaspis melaleucae (melaleuca psyllid) is also being released.[12]
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Melaleuca quinquenervia bark showing the papery exfoliation from which the common name 'paperbark' derives
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Paperbark trees in Tasmania after sunset
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19th century illustration of Melaleuca leucadendra
See also[edit]
- List of Melaleuca species
- Poliopaschia lithochlora, a proposed agent for eradication
References[edit]
- ^ "Melaleuca L.". Germplasm Resources Information Network. United States Department of Agriculture. 2009-01-27. Retrieved 2009-11-10.
- ^ a b Craven, Lyn. "Melaleuca group of genera". Center for Plant Biodiversity Research. Retrieved 2008-04-08.
- ^ "Genre Melaleuca L.". Endémía - Faune & Flore de Nouvelle-Calédonie (in French). Retrieved 2008-04-08.
- ^ Craven, L. (2006). "New Combinations in Melaleuca for Australian Species of Callistemon (Myrtaceae)". Novon: A Journal for Botanical Nomenclature 16 (4): 468–475. doi:10.3417/1055-3177(2006)16[468:ncimfa]2.0.co;2.
- ^ "Tea Tree Oil Information". [dead link]
- ^ "Forces of Nature: Warts No More"[unreliable source?]
- ^ "Tea tree oil (Melaleuca alternifolia [Maiden & Betche] Cheel): Related terms". Mayo Clinic. Retrieved 2012-07-03.
- ^ Langeland, K. A. "Help Protect Florida's Natural Areas from Non-Native Invasive Plants". University of Florida IFAS Extension. Retrieved 2012-07-03.
- ^ "USDA Agricultural Research Service". Retrieved 2012-07-03.
- ^ "The US Department of Agriculture's Australian Biological Control Laboratory". Csiro.au. Retrieved 2012-06-30.
- ^ "Overseas Collections Help Solve Domestic Problems". Retrieved 2012-07-03.
- ^ "Putting The Bite On Melaleuca]: UF And USDA To Release Australian Insect To Control Invasive Tree In South Florida". University of Florida News. April 19, 2002. Retrieved 2012-07-03.
Further reading[edit]
- Hammer KA et al. (2003). "Antifungal activity of the components of Melaleuca alternifolia (tea tree) oil". J. Appl. Microbiol. 95 (4): 853–860. doi:10.1046/j.1365-2672.2003.02059.x. PMID 12969301. CS1 maint: Explicit use of et al. (link)
- Hammer KA et al. (2003). "Susceptibility of oral bacteria to Melaleuca alternifolia (tea tree) oil in vitro". Oral Microbiol. Immunol. 18 (6): 389–392. doi:10.1046/j.0902-0055.2003.00105.x. PMID 14622345. CS1 maint: Explicit use of et al. (link)
- Mondello F et al. (2003). "In vitro and in vivo activity of tea tree oil against azole-susceptible and -resistant human pathogenic yeasts". J. Antimicrob. Chemother. 51 (5): 1223–1229. doi:10.1093/jac/dkg202. PMID 12668571. CS1 maint: Explicit use of et al. (link)
- Oliva B et al. (2003). "Antimycotic activity of Melaleuca alternifolia essential oil and its major components". Lett. Appl. Microbiol. 37 (2): 185–187. doi:10.1046/j.1472-765X.2003.01375.x. PMID 12859665. CS1 maint: Explicit use of et al. (link)
- Takarada K et al. (2004). "A comparison of the antibacterial efficacies of essential oils against oral pathogens". Oral Microbiol. Immunol. 19 (1): 61–64. doi:10.1046/j.0902-0055.2003.00111.x. PMID 14678476. CS1 maint: Explicit use of et al. (link)
• Brophy, J.J., Craven, L.A., Doran, J.C. (2013) Melaleucas: their botany, essential oils and uses. ACIAR Monograph No. 156, Australian Centre for International Agricultural Research, Canberra, 415pp. <http://aciar.gov.au/publication/MN156>
License | http://creativecommons.org/licenses/by-sa/3.0/ |
Rights holder/Author | Wikipedia |
Source | http://en.wikipedia.org/w/index.php?title=Melaleuca&oldid=654333857 |
More info for the terms: cohort, crown fire, fire exclusion, fire suppression, fuel, ground fire, organic soils, prescribed burn, prescribed fire, severity, top-kill, wildfire
Melaleuca invasion may result in changes in fuels and fire behavior relative to what might be expected in native communities. Melaleuca invasion presents novel challenges for fire suppression in southern Florida, mostly related to increased incidence of crown fire, spotting, and ground fire in organic soils [28,102]. Flowers [28] provides a review of fire suppression problems and tactics for melaleuca-invaded sites in southern Florida.
In communities where melaleuca is replacing sawgrass, development of dense melaleuca stands often provides substantial increases in both aerial and surface fuel loads. When fires occur in invaded areas, these changes in fuel conditions may increase incidences of fire spotting. Melaleuca invasion in sawgrass habitats is also implicated in the increased incidence and severity of ground fire in organic soils (see Fuel). Increased burning of organic soils may have serious implications for smoke management due to the volume and intensity of smoke that these ground fires can produce [28].
Fire spread rates may be greater in melaleuca invaded areas, compared with "pine/palmetto/gallberry type fires." This is attributed to a combination of lighter, more easily ignitable ground fuels, peeling melaleuca bark that acts as a ladder fuel, and the increased incidence of spotting [28].
In general, melaleuca management is made difficult by the fact that disturbance resulting in canopy damage in trees of seed-bearing age leads to a rapid purge of canopy-held seed [55]. Of particular difficulty are occasions where understory or ground layer vegetation is also disturbed, such as following fire. Ensuing seedling establishment may initiate a new, often denser melaleuca stand. However, excluding fire (or other disturbance) from established melaleuca stands is probably not a desirable alternative. Although fire exclusion may limit the spread of melaleuca, subsequent successional changes may be undesirable. Further, even with active suppression fire is probably inevitable in the long term [55].
Melaleuca-infested sites that experience wildfire should be given high priority for control, since the postfire environment is probably the most susceptible to melaleuca population increases. The quantity of seedlings established after fire is likely to be huge, and initial growth may be rapid relative to what would occur on an equivalent unburned site. In the event of a wildfire releasing vast quantities of seed, seed trees should be treated with herbicide within 1 postfire year to prevent replenishment of seed stores, then establishing seedlings should be controlled [54]. Saplings that survive the fires may also be treated with herbicides [55].
It is unclear what time interval between fires is feasible or most effective for controlling postfire seedlings. Myers and Belles [54] found a 2-year interval between fires to be effective, although they acknowledged results may differ depending on site productivity. Fuel loads may be too low to carry a 2nd fire for 2 to 3 years, perhaps limiting the effective use of fire as a means to control seedlings (see below). However, field studies did show that gulfhairawn muhly (Muhlenbergia capillaris var. filipes) prairie can be reburned within 2 years and that nearly all seedlings established after the initial seed release event could still be killed (see IMMEDIATE FIRE EFFECT ON PLANT). Follow-up inspections and treatments are likely to be needed [54].
On sites where a prescribed fire is planned, but that contain scattered seed-bearing melaleuca, these "outliers" should be dealt with prior to burning. If outliers cannot first be controlled, burning should be conducted while the soil is still wet enough to stimulate germination, but close enough to the onset of dry season to limit seedling establishment and survival. In addition to surveying for and controlling seedlings that establish after fire, seed trees should be controlled before they replenish seed stocks [54].
Stand structure and age class structure can also be important considerations for mitigating postfire seed release. Mature and emergent melaleuca trees release tremendous amounts of seed after burning, while fires in even-aged "dog hair" stands may burn without releasing many seeds because they produce less seed (see Seed production). "In control efforts where complete stand eradication is not possible in the short term, it may be useful to target mature outliers as well as emergents in dense stands. In other words, remove the trees producing the most seed first. A wildfire in the remaining stand may release relatively few seeds" [54,55].
A study by Myers and others [55] demonstrated the influence of timing, both of burn season and weather/hydroperiod, on melaleuca germination, seedling establishment, and recruitment to sapling status, in the postfire environment. Where seed-bearing trees are present, fire often results in rapid (within 5 weeks after fire) release of most (>95%) canopy-stored seed. Most germination occurs when seeds encounter moist soil. When seeds fall on dry substrate, germination is delayed until the next significant rain event. Because vast quantities of seed are released, large numbers of seedlings may result under optimum germination conditions. However, it appears that substantial seedling mortality is common when the site becomes either flooded or dries. The seasonal weather pattern in southern Florida is relatively predictable. Melaleuca seedling survival is greatest when seedlings establish during the wet season as flood waters wane. Seedling mortality is greatest for cohorts established during the transition from wet season to dry season. But more punctuated weather episodes such as brief droughts or short-lived rainy periods are common as well, and can lead to correlative periods of germination, establishment and mortality. The predictive power of weather forecasting over periods of weeks to months has obvious limits. Nevertheless, planning prescribed fires for times that put seed on the ground when it is least likely to result in newly established melaleuca cohorts is desirable [55].
Melaleuca seedling establishment can be largely controlled using prescribed fire [54]. However, determining the appropriate timing of burn treatments for seedling control can be difficult. Burns must be conducted after seed rain is complete and most germinable seeds have germinated, but before establishing seedlings are large enough to sprout following fire. A general rule governing this timing probably does not exist. Intervals between seed release and seedling establishment, and between establishment and the ability to survive fire, varies among sites, between years, and within a year depending on moisture conditions following seed rain, prefire fuels, seed rain volume and duration, and seedling growth rates [54]. Results of a study by Myers and Belles [54] suggest that seedlings <3 months old almost never sprout in response to top-killing. Also, at any given age, larger seedlings (height or diameter) were significantly (p<0.01) more likely to survive top-kill by fire or clipping, compared with smaller seedlings. Mean height at which seedlings first demonstrated sprouting following burn treatments ranged from 1.9 to 6 inches (4.7-15.2 cm), and mean basal diameter ranged from 0.07 to 0.12 inch (0.17-0.31 cm). For treatment descriptions and detailed results, see [54]. Seedling size may be a more critical metric than seedling age in predicting control effectiveness using fire. Therefore, on sites that support rapid and robust melaleuca seedling establishment and growth, the window of opportunity for controlling seedlings with prescribed fire is likely to be shorter than on less productive sites. Myers and Belles [54] "cautiously" recommended conducting fire treatments within 6 months of seedling establishment on "high quality" melaleuca sites, while suggesting that a 24-month postestablishment window is possible on sites where seedling growth is slowest. In their field studies in Big Cypress National Preserve, they found >90% of seedlings ≤2 years old were killed by fire.
Unfortunately, any seed trees that survive fire may have replenished their store of canopy-held seed by the time enough fuel has accumulated to carry a second fire. Research in Big Cypress National Preserve demonstrated that surviving melaleuca seed trees replenished stores of seed capsules within 2 years after the initial fire, and a 2nd prescribed burn resulted in an additional cohort of establishing seedlings. Depending on the site and the plant community, successive burns may largely stave off establishment of new seedlings, even though mature seed trees remain on site and producing seed [54,55].
Most evidence indicates that a single fire, and perhaps several periodic fires, are unlikely to cause any substantial mortality in mature melaleuca stands (see Fire Effects discussion above). Meskimen [48] related an anecdote about a stand of melaleuca planted as a windbreak around sugarcane (Saccharum officinarum) fields, which were burned each year. While details of fire behavior and effects were not described, he stated that trees were "exposed to extreme heat and sometimes direct fire which causes complete defoliation." These trees displayed no signs of damage other than fire scarred bark, and seemed to exhibit normal growth. Nevertheless, Myers and Belles [54] suggested that the ramifications of a prolonged program of repeated burning in melaleuca stands are unknown.
Disturbances that release the canopy seed bank but leave intact fuel beds offer the best opportunities for seedling and sapling control with fire. Unlike postfire seedling establishment, in which fuels sufficient to kill newly established seedlings are consumed in the original fire, an episode of mass seed dispersal and germination associated with a nonfire disturbance would be accompanied by retention of predisturbance fuels and potential for burning many vulnerable young melaleuca seedlings. On most sites, for instance, regeneration established from seed released due to herbicide-kill or frost-damage could easily be killed by burning [54,104]. Again, burning should be implemented after most seeds have dispersed and germinated but before seedlings have reached a size where many are likely to survive the fire. In some instances germination may be delayed for months due to either flooding or drought, and growth after germination will vary greatly from site to site. Sites where seeds have been released must be monitored to verify that germination has occurred and that seedlings do not exceed a meter in height [54].
Timmer and Teague [93] indicate controlled burning can be used to eliminate seedlings or sprouts that occur following control of adult seed-bearing trees (see the discussion on Control and subsequent information on various nonfire control methods). Tuck and Myers [95] have advocated use of properly timed prescribed fire for melaleuca management. Objectives can include reducing seed crops, preventing flowering, eliminating seedlings, and thinning young stands. They also suggest that herbicides may be more effective on fire-weakened melaleuca than on unburned plants. A melaleuca control program on the Arthur R. Marshall Loxahatchee National Wildlife Refuge in southern Florida has utilized prescribed fire following herbicide application to control seedlings and to further weaken surviving mature trees [46]. Myers and others [55] recommended prescribed burning as a follow-up 2 to12 months after pulling small plants and cutting and herbicide treatments for larger plants. For dense stands, Myers and Belles [54] speculated that burning followed by ground-based foliar herbicide application to sprouts at 3 to 9 months postfire, is more effective than spraying untreated or unburned stands from aircraft.
More info for the terms: basal area, cohort, competition, density, fire management, fire regime, frequency, fuel, hydroperiod, interference, litter, natural, nonnative species, prescribed burn, prescribed fire, presence, seed tree, severity, stand-replacing fire, succession, swamp, top-kill, tree
Impacts: Melaleuca has been called "the greatest exotic weed threat" to wetlands in southern Florida. Its impacts threaten natural areas such as Big Cypress National Preserve and the Everglades. Systematic reconnaissance flights indicated that by 1992 there were 119,000 acres (48,160 ha) of melaleuca-infested habitat in Big Cypress National Preserve [59]. Everglades National Park is 1 of only 3 sites internationally listed by The International Biosphere Reserve, World Heritage, and Ramsar as critical reserves. The native flora of southern Florida represents a unique assemblage of communities. Southern Florida encompasses the only region of the continental United States where temperate, subtropical and tropical floral elements coexist. This unique area has produced approximately 65 endemic plant taxa, many of which are threatened due to habitat diminishment (reviewed by [96]).
Melaleuca's negative impacts in southern Florida largely stem from the species's interference with and displacement of native species [21]. A review by Hofstetter [35] indicates that in the Everglades and southeastern Florida melaleuca may invade "essentially all types of communities, including those where vegetative components appear to be healthy and presumed" to be "comparable to historical vigor." Intact native communities may be more resistant to invasion in southwestern Florida but are still susceptible, particularly following unnatural disturbance or other human-caused environmental degradation.
Presence of melaleuca in fire-maintained sawgrass communities can promote conversion of these habitats to melaleuca forest. Everglades marshlands are comprised of fire-maintained communities of mostly sawgrass prairies. Natural fires periodically eliminate the native, fire-intolerant hardwoods that would otherwise colonize this habitat. However, because melaleuca is so well-adapted to fire it is able to persist and even thrive in this environment, eventually shading out the herbaceous community and transforming the site into a melaleuca forest [96]. See Habitat Types and Plant Communities for more information about specific taxa and communities that are potentially impacted.
Conversion of native forest types to melaleuca forest may or may not impact understory species composition and density, depending on the community invaded. Where invaded and uninvaded forest overstory structure is similar, casual observation indicates that the understory may be relatively unchanged, such as in cypress swamps and pine flatwoods where melaleuca establishment is typically "not dense enough" to alter stand structure. Understory vegetation may be most severely impacted where melaleuca invasion increases forest overstory density or leads to conversion of prairie or savanna to melaleuca-dominated forest, such as in pine flatwoods depressions, sloughs, wet prairies, and the seasonally flooded ecotone surrounding cypress swamps [48].
Conversion of the dominant overstory species as a result of melaleuca invasion in forested habitats may be a more obvious impact. Geary and Woodall [30] indicate "mature" melaleuca stands in Florida "swamps" range from 7,000 to 20,000 stems/ha, and up to 133 m²/ha of basal area. Stands growing on shallow or better-drained soils produce similar stem densities, although volume is "substantially" reduced. Myers [51] described how melaleuca "invades portions of fire-maintained pine and cypress forests in southern Florida, and in some cases appears to pre-empt sites where the native vegetation would normally regenerate following fire. Melaleuca accomplishes this by being the first woody species to get its seed on the ground following a late dry season fire. Once established it forms a dense canopy, shading out or preventing seedling establishment of other species. Melaleuca's shaggy bark and flammable leaves may facilitate burning at a greater frequency than normally took place. The result is the development of a new melaleuca-dominated community maintained by fire" [51].
Strong melaleuca competition in invaded communities may result from greater exploitation of soil resources. Results from Di Stefano and others [20,21] revealed that melaleuca-dominated stands (8-10 years old) contained significantly (p<0.05) more woody species root biomass in the upper 8 inches (20 cm) of soil than nearby grand eucalyptus (Eucalyptus grandis) (9 years old) or slash pine (20 years old) plantation stands, or palmetto prairie. The 3 forested sites contained similar levels of aboveground biomass.
One of the most important factors in the success of melaleuca in southern Florida may be its relationship to fire. Melaleuca is well-adapted to perpetuation in a fire-prone environment, perhaps more so than any dominant native plant species in southern Florida. As a result, Wade and others [104] suggested that if melaleuca is present in a burned stand, and postfire hydrologic conditions are conducive to germination and establishment of substantial numbers of melaleuca seedlings, native species in the new stand may be substantially reduced. Because of its many adaptations to fire, melaleuca may have an advantage over many native species in response to dry season fire, to which many native species are apparently not well adapted (reviewed by [35]). Melaleuca invasion may pose particular risk to fire-dependent communities in southern Florida. Myers and others [55] pointed out that marshes, wet prairies, cypress swamps, and pinelands, all habitats that are susceptible to melaleuca invasion, also are all common habitats in southern Florida that require fire for survival. For more information about melaleuca and fire, see Fire Ecology and Fire Effects.
Geary and Woodall [30] attributed the success of invasive melaleuca in Florida to altered hydrology, as well as altered fire regime. Lowered water tables as a result of drainage and excessive groundwater withdrawals in some areas of southern and central Florida have led to changes in the natural hydroperiod. In many areas shortening of flood duration may have led to increased size and severity of wildfires [104]. In addition, sites experiencing stand-replacing fire are frequently subject to seed rain from established melaleuca trees that were planted as ornamentals. The combination of altered hydrology, altered fire regime, and available seed sources can lead to postfire sites that become fully-stocked melaleuca stands with much reduced native plant presence [30]. Melaleuca invasion may itself alter FIRE REGIMES, as well as fuels [28].
South Florida Water Management District and the U.S. Army Corps of Engineers consider impacts of invasive melaleuca in the littoral zone of Lake Okeechobee when adjusting lake water levels. Lower lake levels may stimulate melaleuca growth and establishment, and prolonged periods of reduced water levels may lead to the expansion of established melaleuca populations (reviewed in [44]).
Ewel [24] has argued that southern Florida may be especially susceptible to invasion by nonnative plants because it is geologically young and not all ecological niches are fully occupied by its indigenous flora. In particular, pondcypress growing on sites that are too wet to support south Florida slash pine, but are drier than is optimal for pondcypress, may be unable to effectively compete with invading melaleuca [24,52]. Pondcypress stands in these ecotones are short, open-canopied, and subject to frequent fires [24]. Myers [52] and Ewel [24] suggest pondcypress in southern Florida occupies sites for which it is not well adapted. Melaleuca invasion in "dwarf cypress" habitats, which are typically a mix of wet prairie and stunted south Florida slash pine and pondcypress, may represent displacement of native species that had occupied "suboptimal sites due to an absence of competition" (see Myers [52] for details). The ecotone between pondcypress and south Florida slash pine forest communities seems particularly susceptible to melaleuca invasion [52].
It is commonly asserted that one reason nonnative invasive plants are so successful is that they are largely unconstrained by the impacts of herbivory from coevolved pests in their native habitat (e.g. a review by Mack and others [45]). Balciunas and Burrows [4] demonstrated how ambient, nonoutbreak levels of insect herbivory significantly (p<0.05) suppressed height and diameter growth of melaleuca saplings in northern Queensland, Australia. They also suggested that reduced levels of herbivory on southern Florida melaleuca, compared with herbivory in Australia where the species is native, might explain part of melaleuca's strong competitiveness in southern Florida's plant communities [4]. Comparative data from melaleuca populations in eastern Australia and southern Florida suggest that seed production is substantially greater in Florida melaleuca trees than those in Australia [74].
Indirect impacts may also result from presence of melaleuca in peninsular Florida. Melaleuca is a host to lobate lac scale (Paratachardina lobata), a nonnative invasive insect pest in southern Florida. Lobate lac scale has a broad host range, attacking well over 100 different woody plants including native species, ornamentals, and crop plants. Damage to melaleuca from lobate lac scale is apparently minimal, but melaleuca can serve as a reservoir for lobate lac scale's infestations of more desirable plants [82].
Although melaleuca has been blamed for human respiratory and allergic reactions [49], a study by Stablein and others [86] concluded that melaleuca is not a significant source of aeroallergen, and melaleuca odor is not a respiratory irritant.
As of this writing (2005), there is very little information indicating whether melaleuca is invasive in areas of North America outside Florida. Woodcock and others [114] described a melaleuca plantation established in the early 1930s on a mid-elevation (869-951 feet (265-290 m)) site on the island of Oahu, Hawaii. The relatively open character of the stand permitted native woody plants to establish in the understory, while excluding more light-demanding nonnative species. It was hypothesized that the melaleuca plantation may be fostering the regeneration of a native successional forest. According to Little and Skolmen [42], in Hawaii melaleuca is "naturalized, but not a pest as in Florida."
Control: The challenge of melaleuca control is influenced by an ever-changing, frequently ephemeral arrangement of environmental conditions, stand structures, seed sources, regeneration status, and fuel loads. Anticipating and identifying windows of opportunity in target susceptibility can enhance success. For instance, treatments for controlling seed-bearing melaleuca may be timed to minimize opportunities for successful seedling establishment resulting from the inevitable postdisturbance seed rain. Treatments that put seed on the ground in late fall or early winter, typically when the soil is still moist from seasonal rains, stimulate germination. Yet many, if not all of the delicate young seedlings are likely to die during the predictably dry months of March, April, and May [54]. Van and others [100] suggested the best time for melaleuca control in southern Florida might be spring, when plants are most actively growing (see Seasonal Development).
Because treating seed-bearing adults inevitably leads to substantial seed release, follow-up treatment or multiple treatments of establishing seedlings will be required to prevent immediate reinvasion. Control activities minimizing disturbance to soil and surrounding desirable plants may help mitigate subsequent melaleuca seedling establishment [93,110] (see Site Characteristics). Myers and Belles [54] point out the importance of field monitoring for knowing a) when germination begins following major seed release, b) whether germination is complete, c) whether additional germination episodes occur following receding flood waters or cessation of drought, and d) size of the largest seedlings in a cohort relative to cohort age. This last point may be important for determining whether the largest seedlings are capable of sprouting in response to top-kill.
Woodall [110] recommended focusing control efforts first on outlying individuals that serve as seed sources for new infestations. Dense, well-established melaleuca stands are more difficult, time consuming, and expensive to eradicate, especially over large areas. Once outliers are eliminated and dense, well-established stands are contained, strategies for complete eradication can be implemented [110].
For areas with scattered, mature melaleuca seed trees that have not recently burned, Woodall [113] recommended killing trees and releasing seed from late October to late December. Moisture provided by occasional winter showers will stimulate germination. Lack of fire will promote plant "competition," resulting in slow-growing melaleuca seedlings. Typical spring drought conditions will kill most germinants. The ensuing summer wet season should stimulate germination of any ungerminated seeds left on the site. These and any remnant seedlings can be removed with prescribed fire during the following dry season [113].
In extremely dense melaleuca stands seed production may be substantially reduced within the dominant age cohort due to shading. However, these stands may also contain larger, older, canopy-emergent individuals that bear large numbers of capsules. It may be prudent to first focus control efforts in these stands on the emergents. Without these, extremely dense stands may pose a comparatively lessened threat of massive seed release [54].
A strategy utilized by resource managers at Big Cypress National Preserve is to delay follow-up treatments in melaleuca control units for 3 years, allowing seedlings an opportunity to reach a height that facilitates detection with a minimal chance of seed production [59]; however, some plants may produce seed at <3 years of age [48].
Prevention: Because melaleuca seed dispersal is typically distance-limited, treatment of outlier trees that occur far from established melaleuca populations may prevent establishment of new, invasive populations. If the outlier is eliminated in such a way that seeds are not released, then the probability of colonization in that habitat is substantially reduced [11]. Woodall [110] describes how, "as one proceeds toward the central denser portion of a melaleuca population, the relative benefits from killing individual trees decline. The biggest payoff is from controlling the most isolated, most distant trees." Biennial inspections of uninvaded areas will help identify melaleuca outliers [110].
Integrated management: A combination of stressors, both natural and human-caused, might be integrated for more effective management and control of melaleuca: "A judiciously timed, integrated approach using chemicals, mechanical means, and fire can be effective. Present control efforts use mechanical cutting followed by a dose of herbicide. Little attention, on the other hand, has been given to the site susceptibility and timing of treatment. Sites should be treated when the seeds would be most unlikely to encounter favorable conditions for establishment. Full advantage should be taken of both fire and frost. Both occur naturally every few years. Fire can be prescribed at practically any time as long as fuel is available. Both destroy melaleuca biomass in leaves, branches, and small diameter stems, all of which are replaced by sprouts. To accomplish this, the tree uses and depletes stored food reserves. If the tree is cut and treated with herbicide while these reserves are low, the energy for sprouting would be lacking and follow-up treatment would be minimal. Due to the time of year, frost-released seed is likely to encounter unfavorable site conditions, and fuel for burning still remains. Treatment of seed trees following frost and prescribed burning should greatly reduce sprouting. A late wet or early dry season prescribed burn would put the seed on the ground at an unfavorable time" [51].
Biological control agents may further reduce melaleuca populations that have been damaged by other means, such as mechanical, chemical, or fire. Center and others [16] described a release site for melaleuca snout beetle where an estimated 51,360 cut stumps "had coppiced profusely." Snout beetles had fed upon an estimated 25% of coppices. Of those plants that were fed upon, damage on 53% was low (generally consisting of nibbling on one or a few tips), damage on 31% was moderate (extensive damage to several stem tips), and damage on the remaining 16% was high (almost all foliage destroyed) [16].
Physical/mechanical: Mechanical clearing or felling of mature melaleuca trees can be an effective means of control. However, to be most effective desirable vegetation should be subsequently established and maintained, and posttreatment seedling control undertaken. Follow-up treatment(s) are required to control stump sprouts [93]. In a field experiment, 98% of melaleuca plants 2.3 to 3.9 feet (0.7-1.2 m) tall sprouted after a single cutting. The month in which stems were cut had no effect on biomass recovery after a single cutting. Following a 2nd cutting (2 years after the 1st cut), melaleuca mortality rates were still ≤27% for all but 3 months of the year. Mortality rates in June, July, and August were 72%, 55%, and 42%, respectively. High mortality in August may have been influenced by flooding during that month [83]. Plants <3.3 feet (1 m) tall may be hand-pulled and should be stacked to prevent sprouting. Plants > 3.3 feet (1 m) tall are best cut with a machete or chainsaw and the cut surface treated with herbicide [55].
According to Timmer and Teague [93], mature trees that are mechanically cleared should be removed from the site and destroyed to reduce seed dispersal and sprouting. However, Myers and Belles [54] cut >5,000 melaleuca trees in the course of field research, and observed sprouting in "only a few" downed stems, all of which were lying on extremely wet soils or floating. In all cases, sprouts died during subsequent drought.
Fire: See Fire Management Considerations.
Biological: One reason frequently offered for the success of nonnative invasive plants is that in their new environment they are freed from the negative impacts of pests and parasites with which they coexisted in their native habitats (e.g. see the review by Mack and others [45]). Balciunas and Burrows [4] demonstrated how ambient, nonoutbreak levels of insect herbivory significantly (p<0.05) suppressed height and diameter growth of melaleuca saplings in northern Queensland, Australia. They speculated that a classical biological control program using Australian insect herbivores should also suppress melaleuca sapling growth in southern Florida, as well as reduce flowering and seed production, and perhaps lower fire tolerance. Several sources suggest that an integrated biological control program will reduce melaleuca's impact on native species [4,70,107].
Preliminary investigation indicates melaleuca has not acquired indigenous herbivores (or other pathogens) at sufficient densities to cause appreciable damage to trees in southern Florida [19]. Yet several organisms, indigenous and introduced, have shown some potential for reducing melaleuca in southern Florida.
Botryosphaeria ribis is an indigenous fungus in southern Florida. It is pathenogenic to melaleuca but is not known to cause "large-scale epiphytotics" on melaleuca in the field. However, B. ribis canker development and tree mortality may be enhanced by stresses associated with drought, low temperatures, or complete defoliation, so B. ribis may enhance the efficacy of other control activities [70]. Although compatibility between the herbicide chemical imazapyr and B. ribis has been demonstrated in-vitro [71], field studies demonstrated that stump regrowth following treatment with imazapyr and B. ribis mixtures were not significantly (p=0.05) different from regrowth of stumps treated with imazapyr alone [72]. It is logical, though speculative, that defoliation by fire may enhance the pathogenic effect of B. ribis infection, suggesting inoculation prior to prescribed fire in melaleuca-infested areas may reduce postfire melaleuca survival. Further research is needed to establish the efficacy of purposeful B. ribis inoculation in concert with other control methods or natural melaleuca stressors.
Puccinia psidii is a rust fungus that occurs on a variety of Myrtaceae throughout the Caribbean islands and North (Florida), Central, and South America (reviewed in [68]). In 1997, P. psidii was discovered on new growth of about 70% of melaleuca trees and saplings over a 1.2-mile (2 km) strip in southern Florida. Trees were 10 to 16 feet (3-5 m) tall, top-killed, and bushy in appearance, with many new shoots [67]. P. psidii can cause defoliation and twig dieback in infected melaleuca [66,67,68]. The P. psidii-melaleuca "pathosystem" may contribute to melaleuca control in southern Florida, especially if integrated into current control programs [68]. Again, research is needed to establish if purposeful use of P. psidii could be useful for melaleuca control.
Lobate lac scale, an invasive exotic insect in southern Florida, is reported to feed on melaleuca, but as of this writing (2005) melaleuca damage has seemed inconsequential [82] (see Indirect impacts).
Balciunas [5] speculated that melaleuca snout beetle may reduce melaleuca's fire tolerance in Florida, especially of saplings, presumably by depleting energy reserves needed for postfire sprouting. The melaleuca snout beetle (Oxyops vitiosa), an Australian weevil, was released as a biological control agent at 13 sites throughout the range of established melaleuca in southern Florida in 1997 [15,16]. Melaleuca snout beetle establishment (as of May 1999) occurred at 10 of these sites [16] (for a comprehensive description of these sites, introduction methods, and establishment results, see [15,16]). Because of slow dispersal rates (≈ 0.6 mile/year (1 km/yr)), melaleuca snout beetle has been collected and redistributed to >150 locations in southern Florida [60]. Both the adults and larvae prefer to feed on young melaleuca foliage. Although larvae develop best on new leaves, the long-lived (>1 year) adults can subsist on less nutritious, mature foliage and stems during quiescent periods of foliage production [60,106]. Eggs and larvae are most abundant in late fall and early winter when susceptible young foliage is most abundant, and are absent or uncommon in spring and summer unless regrowth from damaged trees is present. Females usually oviposit on the surface of young leaves and expanding buds during the flush of young foliage produced after flowering. The resulting larvae pass through 4 instars, each lasting about 5 days (in eastern Australia). Fourth instars crawl or drop from the host plant, burrow into the ground, and pupate for about 11 days (in eastern Australia) [60,64]. Establishment of beetle populations appears hindered on permanently flooded sites due to drowning of larvae when they drop to search for pupation sites [16,60]. Dispersal of newly released populations may be most rapid on sites with scattered melaleuca in open "savanna-like" areas. Open-grown trees with an abundance of new foliage support healthier snout beetle populations, compared to dense stands with a paucity of young foliage [16]. Based on observations in its native range in eastern Australia, Balciunas and others [6] predicted that melaleuca snout beetle would have the greatest impact on sapling size trees in southern Florida. Feeding by larvae on new foliage causes tip dieback, and persistent damage causes loss of apical dominance. Subsequent branching and new growth provides a feedback of additional resources to sustain continual adult and larval populations. Tissue loss and diversion of photosynthetic resources associated with snout beetle feeding appears to limit flowering in mature melaleuca trees [60,62] and may delay reproductive maturity of saplings [62].
The melaleuca psyllid (Boreioglycaspis melaleucae), an Australian native, was released in southern Florida as a biocontrol agent in February 2002 [61,107]. It has established across a variety of melaleuca-invaded habitats in southern Florida, from permanently flooded wetlands to upland pine flatwood sites. Both adults and larvae feed on melaleuca sap, usually feeding at the tips of new twigs [108]. Most damage is attributed to nymphs [61]. "Tender, expanding buds and leaves as well as mature older leaves are destroyed by nymphs. When populations are large, damage may extend to somewhat woody stems" [61].
Eucerocoris suspectus, a Hemipteran native to Australia, was approved for quarantine testing in the U.S. in 1995. Adults and nymphs feed on young melaleuca leaves and shoots [14].
Chemical: Herbicides are among the most effective and widely used tools for controlling melaleuca in peninsular Florida [40]. Herbicides are most effective when integrated within a suite of control measures and strategies. Cost and logistics can make chemical control difficult to implement over large areas of infestation. As Myers and Belles [54] explained, "for small administrative units, like Corkscrew Swamp Sanctuary, portions of Sanibel Island, and some state parks, existing control technologies focusing on herbicides have worked well. For larger units, like Loxahatchee National Wildlife Refuge, the Conservation Area, and Big Cypress Preserve, the sheer scale of the problem has limited control success" [54].
Damage to melaleuca trees from herbicide may induce the release of substantial numbers of canopy-held seeds. Aside from the cut-stump application method, herbicide treatments presumably result in longer periods of seed release, compared with postfire seed rain, because the herbicides act more slowly than fire [55]. Burkhead [13] indicated melaleuca capsules opened within 6 months after stem injection treatment with either hexazinone or triclopyr. Woodall [112] observed differences in the rate of seed dispersal with different herbicides. Seedfall from trees injected with either picloram or dicamba accelerated rapidly following treatment, corresponding to the rapid effect these chemicals had on the health of treated trees, peaking at 2 weeks posttreatment and remaining above baseline level for 10 weeks to 3 months. In contrast, herbicides that cause gradual damage to trees may not affect seedfall as strongly or as rapidly [112]. Although melaleuca capsules are retained in the tree canopy, mature seeds are not connected to the plant's vascular system so herbicide treatment will not impact seed viability [46]. In some cases, control efforts may actually lead to greater spread due to posttreatment seedling establishment [54].
Herbicide treatments are also complicated by the necessity of retreating the trees that sprout [54,93]. While at least some fraction of mature melaleuca trees that are treated with herbicides can survive initial treatment, detailed information about subsequent sprouting is lacking. Herbicide treatments that leave trees standing (i.e. foliar spray, stem injection or soil-applied herbicide) may result in regrowth of canopy foliage and other aerial tissues [13]. Initial application of chemicals to cut stumps (see below) may also be insufficient to prevent stump sprouting, requiring retreatment.
Timing of herbicide application may also be important. Stocker and Sanders [90] suggested that stem injection treatments administered near the beginning of the growing season only affected tissues above the cut line, since transport in the plant was primarily toward the growing shoots at that time of year. Myers and Belles [54] compared effectiveness of 3 foliar-applied herbicides, applied in January, March, May, June, or November, for controlling melaleuca stump sprouts. Imazapyr was generally more effective than hexazinone, and glyphosate was least effective. Imazapyr killed significantly (p<0.05) more trees when sprayed in November (83.1%) or January (79.3%), compared with March (47.8%), June (32.5%), and May (25.0%). Overall, control effectiveness was significantly (p<0.004) greater for larger (greater crown volume) trees. Reasons for variation in treatment effectiveness by month were unclear. Rather than considerations of seasonal effectiveness of herbicides at killing trees, Myers and Belles [54] recommended timing herbicide treatments to minimize the chances for successful post-treatment seedling establishment (see Control and Fire Management Considerations).
Foliar application of herbicides yields inconsistent results and may be ineffective compared with other methods. Foliar-applied herbicides are probably most effective for controlling stump sprouts, or aerial sprouts in dense and/or low-statured stands following disturbance (such as fire) [54]. For dense stands, Myers and Belles [54] speculated that burning, followed by ground-based foliar herbicide application to sprouts at 3 to 9 postfire months, is more effective than spraying untreated or unburned stands from aircraft. They tested 3 foliar-applied herbicides for controlling postfire sprouting on melaleuca trees (1.3 to 8.5 feet (0.4-2.6 m) tall). Trees were sprayed either 3 months after fire (mortality sampled at postfire month 20) or 9 months after fire (mortality sampled at postfire month15). Sites were burned under prescription in March and January. Considering all treatment and burn periods, foliar-applied triclopyr produced significantly (p<0.01) greater mortality (81%) than imazapyr (55%), which in turn produced significantly (p<0.01) greater mortality than glyphosate (19%).
Use of soil-applied pelleted herbicide can control melaleuca and has less site impact than felling and stump treatment. Pelleted herbicide is best for nonseedbearing trees since subsequent seed release is protracted and slow to initiate [110]. Stocker and Sanders [90] found that soil applied pellets of hexazinone and tebuthiuron resulted in 100% mortality of mature trees in periodically flooded habitat.
Stem injection of chemicals is an effective, relatively low-impact melaleuca control method. Injected seed trees purge their canopy-held seedbank relatively quickly. Ideally, most seeds are released within 1 month of injection [110]. Burkhead [13] found injection had little adverse impact on nontarget plant species in experimental plots in Big Cypress National Preserve. Grasses within 1.6 feet (0.5 m) of hexazinone-treated trees were killed but reestablished within 1 year of treatment. Imazapyr, picloram + 2,4-D, triclopyr, and hexazinone have all shown good results when used in stem injection [13,54,90]. Myers and Belles [54] also successfully used stem injection (with Hexazinone) to treat postfire sprouting. Mortality was 96% at 5 months after fire and 98% at 9 months after fire, but this treatment was significantly (p<0.05) less effective when applied at 2 months after fire. See Fire Management Considerations for more information about fire and melaleuca control.
Felling melaleuca trees and applying herbicide to cut stumps is also an effective chemical control method. Woodall [110] recommended picloram + 2,4-D for cut-stump treatment. Laroche and others [40] tested several herbicides for effectiveness when applied to cut stumps. Imazapyr yielded 100% control, while application of triclopyr, glyphosate, or hexazinone resulted in >85% melaleuca mortality. Myers and Belles [54] and Stafford [87] also successfully used imazapyr applied to cut stumps. Stafford described moderate but temporary damage to nearby herbaceous plants. It was speculated that this damage was caused by herbicide uptake from soil or root grafts associated with treated melaleuca stumps, rather than from sloppy spraying. Myers and Belles [54] found that applying herbicide to cut stumps of melaleuca trees that had recently burned was also effective.
Regardless of the herbicide used, Myers and Belles [54] suggested the cut-stump method was "slightly more effective" in killing the target tree than stem injection. Also, standing trees are more likely to disperse seeds over a greater area compared with downed trees. Further, while downed trees can release their seed within 2 weeks after cutting, stem-injected trees may take substantially longer (up to 1 year was suggested) for all branches to die and release seed. Inducing rapid seed release by felling trees results in more rapid germination and establishment of closer (both temporally and spatially) cohorts of seedlings, permitting effective seedling control using a follow-up prescribed fire. With stem injection, seedling establishment may occur over a more extended time period, rendering seedling control using prescribed fire problematic. "If burning is conducted when the earliest established seedlings are still small enough to be killed, all seeds may not have been released from dying (or surviving) trees. Such a burn may also stimulate remaining seeds to be released. These seeds will encounter bare mineral soil, reduced competition, and fuel loads too low for a repeat burn. On the other hand, if the burn is conducted after all seeds are released, some early establishing seedlings may already be large enough to survive the burn.". Stump treatments may also be timed to take advantage of seasonal flooding and the suppressive effects of inundation on stump sprouting [54] (see Cultural control below).
However, Woodall [110] recommended against cut stump treatments for general purposes: "Large amounts of the chemical are needed because the circulation of fluids within the tree stops when the tree is cut. Any herbicide that can prevent stump sprouting can do a much more efficient job when injected into the stem of an otherwise undamaged tree. Stump treatment is advisable when: (1) the stem is too small for injection and the rooting medium is unsuitable for soil application, or (2) the need to remove all seeds is so critical as to require felling. A good example of (1) is a small sapling rooted on a cypress knee; an example of (2) is a large seed tree immediately adjacent to a prepared seed bed, such as the right-of-way of a powerline being constructed" [110].
Melaleuca seedlings can also be controlled with herbicides. According to Timmer and Teague [93] "herbicide treatments using either broadcast foliar sprays or soil treatment may prevent germination and/or establishment" of seedlings. In a greenhouse study, Woodall [109] attained complete kill of 45-day-old seedlings with bromacil, diuron, picloram + 2,4-D, and hexazinone, complete kill of 106-day-old seedlings with bromacil, diuron, and picloram + 2,4-D, and complete or near-complete kill of 106-day-old seedlings with hexazinone. Stocker and Sanders [90] achieved 100% mortality of seedlings between 8 and 24 inches (20-60 cm) tall after 6 weeks following broadcast applications of bromacil, tebuthiuron, and hexazinone, and after 44 weeks using glyphosate.
For more information, a review of specific control methods using herbicides is provided by Timmer and Teague [93].
Cultural: Timmer and Teague [93] indicated that, where water levels can be manipulated, seedlings can be controlled by flooding the treatment area. However, they did not indicate the optimum depth or duration of flooding for effective control. In addition, several studies have shown that melaleuca seedlings can survive complete submersion for several months, indicating that this approach may only be marginally effective unless conducted over a long time.
On the other hand, stump sprouting following felling of mature melaleuca trees may be reduced or even eliminated if stumps are subsequently submerged. Mechanical treatments conducted just prior to seasonal flooding may be particularly useful in dense melaleuca stands with access for large mechanized cutters. For best results, stumps should be submerged within at least 2 weeks of cutting and should be submerged for at least 40 days. If seasonal flooding is insufficient, stump sprouts can be treated with foliar-applied herbicides [54].
Woodall [110] described "forced succession," in which conditions are created that will induce the development of a shade tolerant native plant community, while gradually reducing melaleuca overstory and discouraging melaleuca regeneration. Gradually thinning melaleuca, perhaps over a 10-year period, increases light levels sufficiently to maintain a favorable microclimate, resulting in improved vigor of native seedlings that are likely already present in the understory of melaleuca-dominated stands. Simultaneously, care is taken to maintain a thick, undisturbed litter layer that inhibits establishment of melaleuca seedlings. Thinning may be carried out by felling or chemical stem injection, although felled trees should remain where they fall to prevent undue disturbance. Thinning should remove the largest, oldest trees first to minimize sprouting, since sprouting decreases with age of trees [110].
More info for the terms: fuel, tree
Although melaleuca was previously planted in Florida as an ornamental landscape tree, retail trade in melaleuca has largely ceased [7]. It was planted as early as 1941 on levees and dredged materials islands at Lake Okeechobee, Florida to prevent storm waves from eroding the levees [91]. Melaleuca was introduced in Hawaii for ornamental uses, windbreaks, and as "watershed cover" [42]. It is apparently also cultivated as an ornamental in southern Louisiana, Texas, and California, and perhaps Puerto Rico (see General Distribution).
Melaleuca is an important honeybee plant in southern Florida [30,36,48,77].
Melaleuca chips may be useful as a component of commercial potting medium [12,17,18].
Essential oil is distilled from leaves, twigs, and seeds. The oil has both traditional and modern uses, mainly associated with its antiseptic properties [94]. It has been used for medicinal purposes and as food flavorings [22]. Commercial production of essential oil from melaleuca apparently ceased in 1955 when a Swiss company began producing a synthetic form [9].
Wood Products: Globally, melaleuca has been used for structural lumber, fuel, pulpwood, and insulation/stuffing [22]. It has been used for traditional dwelling construction in New Caledonia. Melaleuca wood has been used extensively for carpentry and joinery work. It is workable mainly while it is still green, becoming extremely hard after drying and ageing. The wood is also resistant to common wood-eating insects [94]. No "significant" industries in Florida utilize melaleuca for any these products [22]. According to Geary and Woodall [30], melaleuca wood products value is diminished by the "quality of its corky bark."
More info for the terms: cover, hardwood, marsh, natural, presence
The importance of melaleuca-invaded habitat for wildlife in southern Florida is unclear. According to Geary and Woodall [30] melaleuca stands "are of dubious value to wildlife." Melaleuca-invaded habitats in southern Florida may support some populations of native rodents, but the value of melaleuca-invaded habitats relative to native habitats for native rodents and their predators remains unclear [47,58].
Schortemeyer and others [79] recorded 30 species of birds from November through April in or near melaleuca study sites in southern Florida. They suggest that melaleuca may provide nesting and roosting sites for anhingas, egrets, and herons, and resting and feeding perches for Everglade kites, in areas where altered hydroperiods have damaged or eliminated natural sites such as willow (Salix spp.) strands.
O'Hare and Dalrymple [57] conducted a comprehensive survey of wildlife in southeastern Florida marshlands across a gradient of melaleuca coverage. Overall species richness was highest in areas with moderate melaleuca coverage (or melaleuca savanna), perhaps due to high levels of structural diversity of vegetation. Much of the observed difference in overall species richness was associated with high numbers of migratory upland birds. Although migratory upland birds apparently favored melaleuca savanna habitat over dense melaleuca stands or relatively uninvaded marsh habitats, species abundance generally remained below that for the same bird species in native forested habitats such as cypress swamps, hardwood hammocks, and south Florida slash pine rocklands. There were no significant (p<0.05) differences between melaleuca cover types in average number of individuals or average number of species of captured macroinvertebrates or herpetofauna. For fishes, there were no significant (p<0.05) differences between melaleuca cover types in average number of species, but average number of captured individuals was significantly (p=0.03) lower in the densest (75%-100% coverage) melaleuca habitats. A shift in species mix of both birds and mammals with melaleuca cover was noted, with more typical marsh species found in the lowest melaleuca cover types and more upland or forest-dwelling species found in the densest melaleuca habitats [57].
According to O'Hare and Dalrymple [57], moderate levels of melaleuca invasion in southeastern Florida native marsh habitats may not necessarily diminish typical native faunal species composition and productivity. As native graminoid/herbaceous wetlands are converted to closed-canopy melaleuca forest, presence of upland, arboreal, and/or forest species increases, but not necessarily at the immediate expense of wetland species diversity. They recommend that efforts to control melaleuca and restore native plant communities be made in ways that recognize the persistence of native fauna in invaded habitats and allow for retention of the extant wildlife community. Nevertheless, Schortemeyer and others [79] suggested that melaleuca wildlife value should not be overstated, since melaleuca's continued spread across the landscape is likely to diminish overall native habitat [79].
As of this writing (2005) there is no published information describing importance of melaleuca for livestock.
Palatability/nutritional value: Relatively low moisture (56%) and high crude fiber contents indicate melaleuca has a low digestibility coefficient and is probably not a desirable deer food [79]. Young foliage is highest in nitrogen content and lowest in percent dry mass, compared with mature foliage [105].
The following table provides chemical analysis, on a percent oven-dry basis, of melaleuca browse material. Samples were collected in spring from the Everglades Wildlife Management Area [79].
Protein | Crude Fat | Crude Fiber | Ash | N-free Extract | Ca | P | K | Mg | Na |
4.95 | 8.18 | 25.34 | 6.51 | 54.97 | 1.93 | 0.06 | 0.42 | 0.20 | 0.31 |
Cover value: No information is available on this topic.