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Invasive Non-native Plants
The forests of the southeastern United States are increasingly
facing the impacts of non-native invasive species (plants, animals,
and pathogens). Many invasive plants affect forest health, productivity,
access and use, forest management costs, and limit species diversity
on millions of acres of southeastern forests. These plants displace
native plants and associated wildlife, and can alter natural processes
such as fire regimes and hydrology. As foresters, landowners,
and land managers we must be proactive and meet this
issue head-on to maintain the health, function and long-term productivity
of our forests.
IMAGES OF FOREST INVASIONS 
PHOTO 1(left): Cogon grass (Imperata cylindrica) invasion
in pine stand, Central Florida.
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PHOTO 2 (right): Old World climbing fern (Lygodium microphyllum)
invasion in Southeast Florida cypress stand. (Image courtesy
of USDA ARS Photolab)
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PHOTO 3 (left): Air potato (Dioscorea bulbifera) invasion in Central
Florida mixed hardwood stand.
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PHOTO 4 (right): Japanese climbing fern (Lygodium japonicum) invasion
in northwest Florida pine plantation.
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PHOTO 5 (left): Kudzu (Pueraria montana var. lobata)
invasion in the Eastern United States. (Image courtesy of www.invasive.org) |
PHOTO 6 (right):Melaleuca (Melaleuca quinquenervia) invasion in Southwest Florida
pine flatwoods.
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WHAT
IS A NON-NATIVE (EXOTIC), INVASIVE PLANT?
Non-native invasive plants are essentially "Weeds in the
Woods" (or in other natural areas). The two characteristics
common to these plants are:
Non-native: Plants which are
not originally from Florida/United States, these plants are
often introduced intentionally or accidentally by human activity.
The most common sources of plant introduction in Florida are:
import for ornamental/horticultural purposes, introduction for
agricultural purposes (forage, erosion control, etc.), and accidental
introduction. Approximately 1/3 of the plant species growing on their own without cultivation in Florida are non-native.
Invasive: Invasive plants are plants which escape cultivation,
become established in a forest or natural area, and start expanding
and reproducing on their own. Once established, these plants often
alter native plant communities, out-compete and kill native species,
or otherwise affect natural ecosystems.
WHY SHOULD I CARE ABOUT THESE PLANTS?
There are many reasons to be concerned about the expanding problem
of invasive species. Whether your primary interest in forestry
is timber production, aesthetics, recreation, wildlife, or a combination
of many benefits, all aspects of forest management can be affected
by these plant invasions. For example, approximately 46% of the
federally listed threatened and endangered species in the United
States are considered to be imperiled in part due to impacts of
invasive species. Economists have estimated that across the globe,
$3-5 trillion may be lost annually to the impacts and management
of invasive species (this figure includes impacts by introduced
plants and animals, diseases, agricultural weeds, and others).
Several of these species either possess the potential to, or have
already begun impacting various forest product industries. An
established example is that of Kudzu, which infests an estimated
7 million acres in the southeast, and costs approximately $500
million dollars in lost farm and timber production annually. The
most recent example of this is the impact the Japanese climbing
fern infestations have begun to have on the pine straw production
industry in Florida. Pine straw producers have had to abandon
leased pine stands in some cases where the Japanese climbing fern
infestation made harvest of a clean and legally saleable product
impossible.
As a state, Florida is at a high risk for invasion
for many reasons. Our subtropical climate, the number and importance
of our shipping ports, the extent and importance of the plant-based
industries in the state, and the highly transitional population,
couple with other factors to facilitate introduction, escape and
spread of these problem plants. In Florida, approximately $30
million taxpayer dollars are spent annually on invasive plant
management on natural areas and waterways.
HOW DO
THESE PLANTS GET TO MY FOREST?
Invasive plants are spread in many ways:
- Humans through movement of equipment, and/or soil contaminated with seeds or roots
- Wildlife (especially deer & birds)
- Cattle
- Water and wind
Forest managers need to be aware of how our actions can
promote the spread of these plants. Many forestry techniques
involve soil disturbance (eg. harvesting, site prep, planting)
and alteration of the canopy (eg. harvesting) which affects
sunlight and water penetration to the soil level, these activities
may aid in the introduction or spread of these species on your
property.
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WHERE MIGHT I FIND THESE PLANTS ON MY FOREST?
Generally the first place you find these
plants is in areas of human activity, such as: forest boundaries,
common dumping sites, old home sites, roadways and ditches,
disturbance areas (timber sales, mining sites etc.), and firelines.
MANAGING INVASIVE PLANTS
There are many reasons to start controlling
these plants on your property. There are both economic and environmentally-based
benefits of controlling invasive plants, such as: reducing further
spread on your property and expansion of your problem, maintaining
the ability to produce forest products on your property into
the long-term future, restoring natural communities and/or forest
health, and complying with state and federal laws.
Preventing invasion on your property
Management of non-native
invasive plants should utilize an integrated pest management
approach, incorporating mechanical, chemical, cultural, and
biological techniques in combination. However, the first and
best step to take, when possible, is to prevent the introduction
or spread of these plants onto your property by making management
decisions that consider the presence or movement of these plants.
Identification and Control Guides
Another key step is to
learn the key problem plants for your area. There are different
preventative action and treatment approaches for each invasive
species. By knowing your "enemy" you can choose the most effective
and efficient approach in managing these plants. Several books,
websites, and other publications are available.
Invasive Plant Laws
Some of these plants are regulated by
state, federal, or local government. respective invasive plant laws that pertain to Florida.
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FLEPPC/DEP INVASIVE PLANT DATABASE: Report non-native invasive plants in Florida's Natural Areas: http://www.fleppc.org/database/data_intro.htm
Prescribed fire, a critically important forest
management tool, may contribute to the spread of some invasive
species such as cogon grass, Japanese and Old World climbing
ferns, and meleleuca, while negatively impacting others. However,
the specifics of the relationship between fire and invasive
plants in land management have not been adequately quantified.
A commonly referenced species which can be readily transported
or promoted through techniques such as: discing, skidding of
timber, chopping, fireline establishment, prescribed burning,
and road maintenance, is cogon grass, a highly problematic species
in Florida and southern Alabama which is slowly expanding its
range in the southeast (Shilling et al. 1998).
Florida Invasive Species Partnership website
FloridaInvasives.org
is an online resource of management assistance programs to help in your fight against problematic plant species. The Florida Invasive Species Partnership has created the website to help connect Florida's land owners and land managers with the best invasive species management programs available. These programs have been collected, evaluated and categorized in a single resource to make it easier for you to find the financial and/or technical assistance that meets your personal needs.
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