The refuge’s climate consists of moderate temperatures with a mean of 89oF in the summer and 56oF in the winter, while extreme temperatures occur occasionally at 20oF and 110oF. The wet season occurs during the months of May and October and the dry season is experienced in the remaining part of the year. Hurricanes usually hit the refuge bringing in large inches of rainfall and strong winds. The Atlantic Ocean, which borders the Eastern end and the surface water of the Everglades, moderates the temperature.
The soil is mainly composed of high organic content Loxahatchee peat and others including Everglades peat and Gandy peat in moderate amounts. Each peat type forms from various debris sources. The native vegetative habitats presented in this park include sloughs, wet prairies, sawgrass, tree islands, cattail and cypress swamp. These were further grouped into 4 categories: marsh, shrubs, tree islands and cattail. Sloughs consist of deep marsh communities while wet prairies are shallower and have different
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vegetation. Sawgrass consists of saw-edged (triangular shaped) leaves, which borders the tree islands. These are a variety of trees that rise above the water’s surface. A representative of this is shown in Appendix A.
In order to further this paper a few definitions should be taken into account:
Native: a species whose natural range included Florida at the time of European contact
Exotic: a species introduced to Florida, purposefully or accidentally, from a natural range outside of Florida
Naturalized exotic: an exotic that sustains itself outside cultivation
Invasive exotic: an exotic that not only has naturalized but is expanding on its own in Florida plant communities
Category 1: Invasive exotics that are altering native plant communities by displacing native species, changing community structures or ecological functions or hybridizing with natives
Category 2: Invasive exotics that have increased in abundance or frequency but have not yet altered Florida plant communities to the extent shown by Category 1 species.
Refer to Appendix B for a list of Exotic, Invasive Animal and Plant Species in the Refuge
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Invasive exotic plants posing a serious threat to the Florida ecosystem and native species in the habitat are the Brazilian Pepper, Old World Climbing Fern, Australian Pine and Melaleuca.
The biologist informed me that the Melaleuca posed the greatest threat because of its heavy infestation in the refuge’s interior. Melaleuca (Melaleuca quinquenervia) is originally from Australia and was introduced in southern Florida as an ornamental plant in 1906. A surprising fact to note is that the Melaleuca is now merging towards extinction in Australia and the few remaining remnants do not grow at its optimum ability. Australian conservationists have not yet decided however if the Melaleuca plants will be taken back to Australia in an attempt to restore a once native beauty. It has been able to survive in Florida very well because of the similarity in the climate and conditions to Australia. It flourishes well in Florida’s seasonal wet sites and standing water. The Melaleuca has been able to grow very green and lusciously in the refuge and in so doing, it takes away nutrients needed by the native species.
In order to make way for agriculture and development, the Everglades had to undergo extensive drainage. The characteristic of the tree to be able to take up and use water rapidly during photosynthesis and transpiration proposed assistance capabilities in the drainage activity. It is now believed to have infested 3 million acres. Habitats invaded in the refuge include the cypress swamp, sawgrass, wet prairies, tree islands and sloughs. Melaleuca produces seeds in about 2-3 years and can store 20 million seeds at maturity. Seeds are dispersed by wind and water and the trees are currently expanding at a rate of
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10 acres per day and if not treated, it will take over the refuge. Please refer to Appendix A for illustrations on Melaleuca distribution.
As mentioned earlier, the Melaleuca grows ideally in its Floridian habitat and is only more encouraged, as it is not endangered by other species of plants and animals. However, it in turn poses a threat to the native flora and fauna. Various methods have been proposed so far to assist in the eradication process of this plant pest. These methods include biological, manual, mechanical, physical and chemical controls, with the latter being the most successful.
Biological control involves the use of insects originating from Australia such as the Snout Beetle and the Defoliating Snout Fly. The advantage of both of these insects is that they feed ravenously on the seeds and leaves of the Melaleuca tree and thus reduces the rapid spread of the plant. However, they both come with their disadvantages. The beetle cannot survive and reproduce in the wetlands, while the sawfly threatens animal species that have consumed large quantities causing them to contract the insect’s toxin, Lophrytonin that builds up in their system. People still grow Melaleuca for use in landscaping and the sawfly may eradicate this already controlled feature.
Manual removal is possible for seedlings and small trees but is quite labor intensive and is of no guarantee since root fragments usually re-sprout. Mechanical removal involves the use of heavy machinery for the mature trees. It is very risky, as seeds released have to be destroyed and the soil has to be restored. Follow-ups are necessary to prevent reinvasion.
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Fire, the physical control, is not a very good tool as the oils contained in the Melaleuca foliage allow the fire to burn uncontrollably and in addition to this problem,
huge amounts of seeds are dispersed. Fires may control small seedlings but mature trees are quite fire enduring.
Chemical control, that is, the use of herbicides is the main method of eradication. The trees are usually cut down and treated with a sufficient calculated amount of chemicals needed. The chemicals/herbicides used include Arsenal, Banvel 720, Garlon 3A, Rodeo, Spike (40P, 20P & 80W) and Velpar L. Each chemical has its own specifications for the age of tree to be treated, the amount and dilution, application and re-application methods and the effects on neighboring vegetation. Treatment is limited to ½ -1 acres per day, which is of relatively little significance in comparison to its spreading rate. It costs more than $200,000 annually and approximately only 6400 acres have been cleared thus far. Appendix C provides color illustration of the eradication process for Melaleuca.
In the refuge’s attempt to successfully control its exotic plant situation, continual funding is surely a necessity. The refuge is open to volunteers who would like to assist in the eradication program and we as Floridian residents should take the opportunity to preserve our natural habitats because surely the effects of these exotic species will reflect on the future and ourselves.
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Works Cited
“Florida Exotic Pest Plant Council’s 2001 List of Invasive Species.” Online. Compuserve. 15 Feb. 2001. Available FTP: .
Langeland, Ken A., et al. Exotic Woody Plant Control. Florida: U of Florida: C.M. Hinton Publications Distribution Center, 1990.
Krebs, Charles J. Ecology. 5th ed. Canada: University of British Colombia, 2001.
Thomas, Bill. Personal interview. 8 Feb. 2001.
Thomas, Bill, et al. Arthur R. Marshall Loxahatchee National Wildlife Refuge: Comprehensive Conservation Plan. Florida, 2000.
Troyka, Lynn Quitman. Simon & Schuster Handbook for Writers. 4th ed. New Jersey: Prentice Hall, 1996.
Appendices
Appendix A- Comprehensive Conservation Plan
Appendix B- Flora and Fauna
Appendix C- Eradication Procedures for the Melaleuca
Appendix D- List of Exotic Pest Plants in Florida.
