Land
Management Program at Archbold Biological Station
P.O. Box 2057, Lake Placid, FL 33862
Phone 863-465-2571 FAX 863-699-1927
E-mail: landmanager@archbold-station.org
Giant Reed (Arundo donax)
The proposed planting of 8,000 acres of giant reed (Arundo donax) in Highlands and DeSoto Counties, Florida has the potential to disrupt the natural communities in which many listed species of flora and fauna occur. The Lake Wales Ridge is considered one of the hotspots for biodiversity in the United States and home of many endemic species of flora and fauna (Dobson et al. 1997). Archbold Biological Station is located in Highlands County at the southern end of the Lake Wales Ridge. This area, including Highlands County, is one of the sites being considered as a potential introduction site of giant reed for agricultural purposes. Invasive plants combined with altered hydrology and habitat fragmentation have led to major changes in Florida’s natural communities (Schmitz et. al, 1997; Austin, 1999).
Giant reed spreads primarily by vegetative means (rhizome fragments) though little is known about sexual reproduction of this plant, most prominently seed viability, dormancy, germination rates, or seedling establishment (http://www.nps.gov/plants/alien/fact/ardo1.htm). Giant reed can tolerate a wide range of soils and moisture levels making it a potential invasive plant of seasonal wetlands and pine flatwoods communities along the Lake Wales Ridge and adjacent areas. Though it thrives in moist soils, it apparently grows well in upland sites (Miller, 2003) making it a potential invasive plant of scrub and sandhill communities along the Lake Wales Ridge that support many listed species. Giant reed has formed hundred acre monocultures on South Pacific Islands and responds favorably to fire, often resprouting rapidly and eliminating all native plants (http://www.hear.org/pier/ardon.htm). Most of the natural communities along the Lake Wales Ridge and Florida are fire dependent systems; thus, the large scale introduction of giant reed into Highlands and DeSoto Counties could eventually increase and alter the fire regimes of many natural communities.
Currently, few plants have invaded xeric habitat of the Southern Lake Wales Ridge, but some plants have slowly invaded communities such as scrub and sandhill. These invasive plants occurring in xeric habitat of the Lake Wales Ridge are dominated primarily by grasses including the following species: torpedo grass (Panicum repens), cogon grass (Imperata cylindrical), para grass (Urochloa mutica), natal grass (Rhynchelytrum repens), Guinea grass (Panicum maximum), smutgrass (Sporobolus indicus), vaseygrass (Paspalum urvillei), and stargrass (Cynodon spp.). Two of these species, torpedo grass and para grass, are considered primarily invasive aquatic plants but are also highly invasive in upland sites, exhibiting diverse habitat variability similar to giant reed. Both torpedo grass and para grass were introduced as forage grasses for cattle. Guinea grass was also introduced as forage crops for cattle, but escaped and invaded natural communities. Torpedo grass, para grass, and Guinea grass are all listed by the Florida Exotic Pest Plant Council as being invasive. Natal grass was introduced for hay production but was abandoned when more productive grasses were discovered, though the species had already escaped into natural areas (Austin, 1978). These examples strongly indicate that well intentioned introductions can result in negative impacts to natural communities.
Other grasses that are considered highly invasive in Florida, such as Burma reed (Neyraudia reyaudiana) and Napier grass (Pennisteum purpureum), have escaped cultivation and invaded natural areas, altering the fire regimes of natural communities such as pine rocklands and prairies. Both of these grasses exhibit traits similar to giant reed that include forming dense clumps, spreading primarily by rhizomes, producing few if any viable seeds, and adaptability to a wide range of soils (Langeland and Burks, 1998). Napier grass occurs in several large clumps and appears to be slowly spreading in xeric habitat along Old State Road 8 about 400 yards from Archbold Biological Station.
Once established, introduced plants become very difficult and costly to control and eradication is almost impossible. Prior to 2001, the State of Florida spent ca. 14 million dollars controlling invasive upland plants on State Lands and it is estimated that > 25 million dollars will be required in the 2003-2004 fiscal year alone to control invasive aquatic plants (http://www.dep.state.fl.us/lands/invaspec/index.htm). In addition, private land owners also spend a great amount of money controlling invasive plants from agricultural and natural sites.
Allowing an exotic plant, such as giant reed, that is documented to be invasive in California and Virginia should be reconsidered. This plant is listed as invasive in sub-tropical (California) and temperate (Virginia) climates in the United States, making it a highly adaptable plant that can withstand a wide range of environmental conditions. At a minimum, a rigorous screening process should be employed similar to those used to test biological controls agents using a variety of test plots (different soils, moisture levels, temperatures, etc.) to test the invasiveness potential of giant reed before this plant is allowed to be used as an agricultural crop. Additionally, field tests should be conducted using herbicides that demonstrate a 100% mortality rate of this plant in the event this plant escapes into natural areas.
There are examples of plants now considered highly invasive that occurred at low densities for decades until a population explosion occurred and the plant began invading natural areas (reviewed in D.A. Gordon and K. P. Thomas, 1997). Brazilian pepper was present in Florida for 50 years before being identified as a problematic species. Several species of fig trees (Ficus spp.) were present in Florida for 4-6 decades before producing viable seeds once their pollinators were introduced. So even though a plant occurs in an area at low population densities now, does not mean that the plant population will not dramatically increase in the future.
Most plants that have become highly invasive are a direct function of their relationship to man and his interests (Austin, 1978), but the long-term effects go far beyond the initial monetary gain. There are few, if any, examples of a now highly invasive plant that was accidentally introduced. Land managers and natural resource specialists in Florida and throughout the southeastern United States are in a constant struggle to win the battle against invasive plants. For the most part, these efforts seldom succeed. The ability to predict the invasive potential of an introduced plant and long term control costs involves many variables (environmental, demographic, and stochastic) and all proposed introductions of nonnative plants should go through a stringent screening process before allowing the introduction of an exotic plant into the Florida or any other area.
References
Austin, D. F.
1978. Exotic
plants and their effects in southeastern Florida.
Environmental Conservation 5: 25-34.
Austin, D. F. 1999.
Displacement of native ecosystems by invasive alien plants -
The Florida experience, or how to destroy an ecosystem.
Proceedings of a Joint Conference of the Florida Exotic Pest
Plant Council and the Florida Native Plant Society (Eds. D. T. Jones and B. W. Gamble). South Florida Water Management District, West
Palm Beach.
Dobson, A. P., J. P. Rodriguez, W. M. Roberts,
and D. S. Wilcove. 1997.
Geographic distribution of endangered species in the United
States. Science 275:
550-553.
Gordon, D. A., and K. P. Thomas. 1997.
Florida’s invasion by nonindigenous plants: history,
screening, and regulation. Pages
21-37 in D. Simberloff, D. C. Schmitz, and T. C. Brown (eds.)
Strangers in Paradise. Island
Press, Washington, D.C.
Langeland, K. A. and K. C. Burks. 1998.
Identification and biology of non-native plants in
Florida’a natural areas. I.F.A.S.
Distribution Center, University of Gainesville, Florida.
Schmitz, D. C, D. Simberloff, R. H. Hofstetter,
W. Haller, and D. Sutton. 1997.
The ecological impact of nonindigenous plants.
Pages 39-61 in D. Simberloff, D. C. Schmitz, and T. C. Brown
(eds.) Strangers in Paradise. Island
Press, Washington, D.C.
FOR MORE INFORMATION ON GIANT REED, CLICK ON THE SITES BELOW:
http://www.nps.gov/plants/alien/fact/ardo1.htm
(General information)
http://tncweeds.ucdavis.edu/esadocs/arundona.html
(General information with links to the ecology and management of Arundo
doanx)
http://ceres.ca.gov/tadn/
(General information and links to pages about the problems Arundo
donax has caused in California)
http://www.invasivespecies.gov/profiles/giantreed.shtml
(General information and links to other sites about Arundo
donax)
http://www.teamarundo.org/ecology_impacts/arundo_ecology.html
(Managment of Arudo donax in California)
http://www.biologie.uni-hamburg.de/b-online/e02/rhizom.htm
(Photo of rhizomes)
http://www.hort.purdue.edu/newcrop/duke_energy/Arundo_donax.html
(Uses of Arundo donax)
• Hutchinson, J.T., August
2003.
© Archbold Biological Station, 2003 April.
• Webmaster: Fred Lohrer, email: webmaster@archbold-station.org