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Magnoliopsida
Melaleuca quinquenervia (Cav.) S.T. Blake
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UNITED STATES
CA | FL | HI | IA | TX | PR |
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This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):
ECOSYSTEMS [29]:
FRES12 Longleaf-slash pine
FRES41 Wet grasslands
More info for the terms: adventitious, crown residual colonizer, root sucker, shrub, tree
POSTFIRE REGENERATION STRATEGY [88]:
Tree with adventitious bud/root crown/soboliferous species root sucker
Tall shrub, adventitious bud/root crown
Crown residual colonizer (on-site, initial community)
4.5 Reproducción
Melaleuca spp. tiene flores hermafroditas proterándricas. Son polinizadas principalmente por insectos pero también por aves y pequeños mamíferos. (Butcher et al., 1992). Las cápsulas de M. quinquenervia contienen un gran número de semillas que pueden ser almacenadas y liberadas si ocurren incendios u otros disturbios, las semillas pueden permanecer en los árboles por más de 10 años. Las semillas permanecen viables en el suelo entre 2 y 3 años, con excepción de localidades que se inundan por temporadas o permanentemente (ISC 2011).
License | http://creativecommons.org/licenses/by-nc-sa/2.5/ |
Rights holder/Author | CONABIO |
Source | No source database. |
Habit: Tree
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This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):
BLM PHYSIOGRAPHIC REGIONS [8]:
None
Paperbark tree tolerates most subtropical ecosystems, preferring wet to intermittently wet sites.
More info for the terms: basal area, capsule, competition, density, fire regime, fire severity, fuel, litter, natural, organic soils, prescribed fire, presence, severity, surface fire, swamp
Fire plays an important role in regulating the structure and function of plant communities in southern Florida [56,104]. According to Meskimen [48], "the ability of melaleuca to withstand fire cannot be questioned, and it is probable that its existence and perpetuation are actually favored by fire." Myers and Belles [54] also suggested "melaleuca's spread is facilitated by fire."
Fire adaptations: Melaleuca possesses several traits that permit its survival following fire, and perhaps even aid in its perpetuation and spread.
Bark characteristics: Two distinct characteristics of melaleuca bark are considered important fire adaptations. First, the thick, spongy, multilayered bark can hold considerable moisture, particular within the innermost layers. This protects the cambium from heat damage during a fire [24,51,94,96,102], allowing the plant to recover via epicormic sprouting along sections of undamaged stem (see Plant Response to Fire). The thickest, most moisture-laden bark is found around the bole and large branches of mature trees, and cambium underlying such bark is well protected. Younger, thinner branches on mature trees and most bark-covered surfaces on younger plants are more susceptible to heat-damaged cambium [52]. Only tissues within "a few millimeters" of the bark surface are susceptible [48]. According to Van and others (unpublished data, as cited in [99]), "large" variations in melaleuca bark thickness have been observed "at different sites" in southern Florida. Paradoxically, in addition to providing protection from fire, the dry, shaggy outer layers of bark are highly flammable and provide a ladder fuel that can quickly carry fire into the canopy, destroying leaves and branches [51,94,102]. It is suggested that where melaleuca invades forested habitats in southern Florida, this structure is likely to increase probability of lethal crown fires that are uncommon in native southern Florida forest communities [104] (see FIRE REGIMES). |
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Photo courtesy the South Florida Sun-Sentinel 2005 |
Serotiny: Melaleuca stores mature seed in closed capsules that remain attached to the branches until they are desiccated [96,102]. Although natural twig mortality causes continual release of some seeds, fire triggers release of millions of seeds [102]. Postfire seed release is apparently triggered by vascular injury to the capsule [48]. Capsules are unlikely to ignite due to their dense, woody structure and the short residence time of most crown fires. Seeds are held in the capsule until several days after the fire, so few seeds are exposed and consumed in the fire [102]. Capsules begin opening within a few days postfire [51]. Most canopy-held seeds are released during the first several weeks following fire [54,55]. As of this writing (2005) no direct evidence exists linking fire severity with the proportion of canopy-held melaleuca seed released following fire. Nevertheless, assuming that seed release is triggered by an injury-induced break in the vascular connection between the capsule and the plant, it is logical to assume that the degree of injury, which itself is proportional to intensity and duration of heating, is closely related to the proportion of canopy-held seed released. For more information see Seed dispersal.
Postfire germination and seedling establishment: Melaleuca can yield a rapid and prodigious postfire seed rain that, coupled with postfire site conditions that are conducive to germination and seedling establishment, can subsequently establish sizable populations of melaleuca seedlings. Melaleuca is one of the 1st postfire species to colonize in many southern Florida habitats [52]. Postfire conditions of reduced competition and ash-enriched soil are likely to promote establishment and rapid growth of seedlings [96]. Results from field studies in Big Cypress National Preserve suggest melaleuca germination is greater on recently burned sites compared with similar unburned sites where vegetation, litter, and periphyton are intact [51,54,55]. Meskimen [48] observed that "densest pockets of melaleuca seedlings occur around seed trees which bear the scars of recent grass fires." In a field study located in wet prairie-dwarf cypress habitats in Big Cypress National Preserve, Myers and others [55] observed substantially greater melaleuca germination where seeds were hand-dispersed within 30 days following prescribed fire, compared with adjacent unburned plots. Recruitment beyond seedling stage was extremely low in both treatments due to subsequent dry or flooded conditions. Hartman [34] examined seedling establishment following a fire in a stand of 6 melaleuca trees approximately 20 feet (6 m) tall, 3 of which survived fire. By 9 postfire months, seedling density ranged from 0.5 to 4.7/m² in a 10 m² area around the surviving trees. At 21 postfire months, an average of 58% of seedlings initially surveyed (at 9 postfire months) had survived. Myers [51] described how seed dispersed following a late-dry season fire is most likely to yield a successfully established stand of new melaleuca seedlings: "Rapid germination after initial moisture application would be an advantage to seed released at the beginning of the wet season, especially if the soil remains moist to wet but not flooded for any extended period. Massive amounts of melaleuca seeds are most commonly released following a late dry season fire. This puts the seed on the ground at the most opportune time" [51]. For more information see Regeneration Processes and Plant Response To Fire.
Postfire sprouting: While foliage, twigs, and smaller branches may be consumed or severely damaged by fire, they are rapidly replaced by new growth originating from epicormic buds on the main stem and larger branches [24,30,48,51,52,53,102]. Even seedlings may have some ability to recover from fire-caused injury by sprouting from the base [48]. Any melaleuca plant that survives fire is well positioned to exploit the postfire nutrient pulse through its existing root system [102]. For more information see Asexual regeneration and Plant Response To Fire.
Fuel: Melaleuca invasion may alter FIRE REGIMES (see below) in southern Florida by changing fuel conditions. In doing so, site conditions may be influenced in ways that favor melaleuca at the expense of native species.
One way melaleuca invasion can alter fuels is by increasing surface litter. Flowers [28] indicates replacement of sawgrass by melaleuca in southern Florida substantially increases surface fuel loads. These changes in surface fuels may increase ignition of organic soils, "a condition that is much less common in the cooler burning sawgrass fires" [28] and often lethal to sawgrass [53]. A review by Greenway [33] suggested that litterfall in some melaleuca forests in eastern Australia is among the highest recorded for Australian temperate/subtropical sclerophyll forests. Van and others [100] monitored litterfall at 6 melaleuca-dominated wetland forest sites in southern Florida. Total litterfall averaged 8.3 tonnes dry weight/ha/yr (range 6.5-9.9 t/ha/yr in 3 different habitats) from July 1997 to June 1999. Average proportions of litter components over 2 years were: leaves 70%, small wood (<0.4 inch (1 cm) in diameter) 16%, capsules 8%, bracts (both floral and foliar) 4%, and flowers 3%. Litterfall biomass was significantly (p<0.001) greater in seasonally flooded (9.9 t/ha/yr) habitats than in either nonflooded (7.5 t/ha/yr) or permanently flooded (8.0 t/ha/yr) habitats [99]. Litterfall occurs year round, but generally increases during dry and windy periods [33,99].
Changes in aerial fuels resulting from melaleuca invasion, coupled with flammable bark that serves as ladder fuel, may also alter fire severity in ways that favor melaleuca. Wade [102] suggested that the combination of loose flammable bark and volatile foliage result in a high propensity for torching of melaleuca trees during fire. In addition, melaleuca frequently establishes extremely dense stands (several thousand stems/acre), making them highly susceptible to running crown fires [102,104]. Extensive areas of southern Florida contain major vegetation types that are primarily adapted to surface fire (see Myers [53]). However, as discussed above and below, melaleuca is well adapted to survive most fires regardless of severity.
In addition to litterfall data [100] (see above), information on melaleuca allometry is available for estimating melaleuca live fuels. Van and others [99] measured stand characteristics and biomass at 6 sites in southern Florida. These sites were blocked in pairs according to hydrologic conditions (dry, seasonally wet, and permanently wet habitats). Stand characteristics varied substantially between sites. Basal area ranged from 78.4 to 190.9 m²/ha, plant density ranged from 8,000 to 132,200 individuals/ha, and aboveground biomass ranged from 129 to 263 t/ha. Regression equations for estimating aboveground biomass, based on stem diameter, height, and dry weight, did not differ significantly (p=0.2017) by site. For regression equations and site-specific data see [99]. Rayachhetry and others [69] also provide detailed information on melaleuca allometry in southern Florida habitats.
FIRE REGIMES: Melaleuca invasion in southern Florida is of major concern, in part because the presence of melaleuca may alter native FIRE REGIMES. For example, melaleuca invasion in pine flatwoods can alter the major native fire regime of frequent (1- to 5-year return interval), low-severity surface fires, instead becoming a mixed regime with less frequent (<35 to 200-year return interval) fires and greater incidence of crown fires. Crown fires are typically nonlethal to melaleuca trees but usually result in pine mortality [53]. As Myers [53] explained, "fire in stands of melaleuca containing any mature capsule-laden individuals leads to the spread of the melaleuca forest into susceptible habitats nearby, resulting in a shift from a fire regime controlled by surface fuels to one dominated by aerial fuels. This is a fire regime heretofore unknown in the Florida environment and is likely to result in significant changes to wetland habitats, especially the species composition. Once melaleuca gets a foothold in a pine- or cypress-dominated habitat, the shift from low-intensity to high-intensity fire regime results in the mortality of the native pine and cypress and subsequent conversion to melaleuca" [53].
The melaleuca fire regime is difficult to categorize. Myers [53] classified the fire regime in southern Florida melaleuca forests as mixed-severity to capture the variation in fire severity among these habitats: "The fire regime mediating Florida's melaleuca forests varies from one characterized by low-intensity surface fires in savannas, with some torching of individual trees, to high-intensity crowning fires in denser stands." "Understory burns occur in melaleuca savannas. In mixed stands of melaleuca and cypress or pine, the fires are lethal to cypress or pine but not to melaleuca. In pure melaleuca forest, high-intensity crowning fires are not lethal to the main stem of the trees. The combination of limited stem mortality and high-intensity fire is unusual in North American ecosystems. Placing melaleuca forest in the mixed fire regime is a compromise between low mortality and high intensity" [53].
Research is needed to ascertain the impacts of melaleuca-mediated changes in fire regime on biotic and abiotic components of southern Florida's ecosystems. For example, does melaleuca invasion result in significant levels of organic soil consumption resulting from severe ground fires, compared with areas of intact native flora? If so, what ecosystem changes are wrought by such reductions in organic soils?
Although melaleuca has evolved several adaptations that permit its exploitation of fire within the plant communities and ecosystems of southern Florida, the relationship between melaleuca and fire in its native habitats is unclear. Seasonal swamp forests and woodlands in northern Australia that are dominated by Melaleuca spp. are "adapted to regular fire" [89], although the occurrence of Melaleuca quinquenervia appears limited mostly to eastern Australia (see General Distribution). A review by Meskimen [48] indicates that melaleuca is a fire-seral species in at least parts of its native range. However, Balciunas and Burrows [4] suggested that in eastern Australia it "is considered fire intolerant, and natural stands are confined to wetlands." It was further asserted that melaleuca fire tolerance in Australia is reduced by stress associated with insect herbivory, and that perhaps a classical biological control program using Australian insect herbivores could reduce melaleuca's fire tolerance in southern Florida [4].
The following table provides fire return intervals for important plant communities and ecosystems where melaleuca might be found in peninsular Florida.
Community or Ecosystem | Dominant Species | Fire Return Interval Range (years) |
mangrove | Avicennia nitida-Rhizophora mangle | 35-200 |
Everglades | Cladium mariscus ssp. jamaicense | <10 |
melaleuca | Melaleuca quinquenervia | 53] |
slash pine | Pinus elliottii | 3-8 |
slash pine-hardwood | P. elliottii-variable | 103] |
South Florida slash pine | P. elliottii var. densa | 1-5 [53,103] |
longleaf-slash pine | P. palustris-P. elliottii | 1-4 [53,103] |
longleaf pine-scrub oak | P. palustris-Quercus spp. | 6-10 [103] |
oak-gum-cypress | Quercus-Nyssa-spp.-Taxodium distichum | 35 to > 200 [53] |
southeastern oak-pine | Quercus-Pinus spp. | < 10 |
live oak | Q. virginiana | 10 to103] |
cabbage palmetto-slash pine | Sabal palmetto-Pinus elliottii | 53,103] |
baldcypress | Taxodium distichum var. distichum | 100 to > 300 |
pondcypress | T. distichum var. nutans | 53] |
Melaleuca quinquenervia primarily propagates by sexual seed production. The species matures rapidly, and is capable of flowering within three (and as little as two) years of germination and as frequently as five times each year (Meskimen 1962, Laroche 1994b). In South Florida, the species blooms primarily during the winter months (November-January), although it is capable of some flowering throughout the year. Flowering is asynchronous both among trees and among the flowers of a single specimen (FLEPPC 1999).Large M. quinquenervia specimens have a very high reproductive potential and up to 20 million seeds per year are stored in the seed capsules of a single tree. Seed capsules must be dried out before they can release seeds to the environment. Seeds can remain viable within seed capsules for several (at least ten) years (Meskimen 1962, Langland and Burks 1998).Physical damage such as broken or cut branches will trigger the rapid release of seeds from capsules on the injured branch. If a tree is felled or experiences a hot-burning fire this will trigger the shedding of all seeds within a few days (Woodall 1983).
License | http://creativecommons.org/licenses/by-nc-sa/3.0/ |
Rights holder/Author | Text can be freely copied and altered, as long as original author and source are properly acknowledged. |
Source | http://www.sms.si.edu/irlspec/Melaleuca_quinquenervia.htm |
Habit: Tree