IFAS Assessment of the Status of Non-native Plants in Florida's Natural Areas
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IFAS Assessment of the Status of Non-native Plants in Florida's Natural Areas

   

IFAS Assessment of the Status of Non-native Plants in Florida's Natural Areas1

Alison M. Fox, Doria R. Gordon, Joan A. Dusky, Linda Tyson, and Randall K. Stocker2

This publication is available in its entirety in PDF format only.

Click here to print or view the entire publication. Current results of the IFAS Assessment and a summary of its conclusions are available on the Center for Aquatic and Invasive Plants Web site at: http://plants.ifas.ufl.edu/assessment.html.

Purpose

The purpose of this assessment is to provide a well-defined mechanism by which all IFAS Extension publications can conform in their description and categorization of non-native plants that are invading natural areas in Florida. Conclusions derived from this assessment are intended to prevent, or reduce, the likelihood of further invasion of natural areas by non-native plants. Development of a common basis for decisions will increase consistency and understanding of recommendations made by IFAS personnel concerning invasive, non-native plants. This assessment has rigorous requirements for documentation to support all relevant evidence and this reinforces the transparency and credibility of the process. It is intended that this assessment will be useful in developing priorities for research and management efforts, and that it can be adapted for use in other states (i.e., with appropriate zonal definitions).

This assessment is not a predictive instrument but is intended ONLY for plant species or cultivars that currently occur within Florida. It is not intended to provide evaluations of species that have not yet been introduced to the State. Such species would require a separate predictive instrument, still to be developed.

It is likely that less than 1% of all non-native plant species in the State will be identified as showing ecological impacts in natural areas (for definitions of terms as used in this document see Glossary, pages 25 - 27). This assessment is designed to identify those non-native species that are invasive in areas of Florida with designated management objectives that include the conservation of native biodiversity. While a range of activities may be conducted in these areas, those activities are designed to be compatible with the conservation objective. State and local governments and some private landowners, for example, manage natural areas both for recreation, grazing, forestry or other harvest values and for conservation values. These areas would be included in the assessment of invasion, with clearly identifiable edges disregarded. Species that invade only adjacent to roads, trails, fire lanes, recent dredge spoil, expanses of bare soil, etc. should not be identified as invaders with impacts in natural areas because their persistence and spread is only in these anthropogenically disturbed zones in the natural area. Species that spread along these artificially disturbed zones but disperse over 10 yards into more intact natural areas would be required to be evaluated by this assessment.

It is also recognized that some anthropogenically disturbed areas can provide habitat for species of special concern; thus in considering broad conservation objectives, it may still be necessary to review non-native species that have not been identified in this assessment as invading natural areas. For example, where Threatened or Endangered species are now predominantly found and maintained in anthropogenically disturbed areas, it is possible that these could be impacted by non-native species that are described by this assessment as "Not considered a problem species at this time". Such cases should be referred to the Florida Endangered Plant Advisory Council (Secretary: Danny Phelps, FL Department of Agriculture and Consumer Services, Division of Plant Industry, Tel: 352-372-3505.)

Objective

The objective of this assessment is to summarize relevant ecological, management and economic value information on species. The intention is to provide a level of information divided into relevant categories that is greater and more functional than that indicated by simple presence or absence from an "Invasive Species List." This information is summarized by four indices, Ecological Impacts, Potential for Expansion, Difficulty of Management and Economic Value. Where possible, predictive items have been avoided. Most questions have been reduced to simple two (or occasionally three) choice answers. This assessment does not address economic impacts other than management costs and economic value. Such data (lost revenue, management costs other than control in natural areas, etc.) should be included in any detailed risk-benefit analyses of the current, or future, infestations of a species.

This assessment will be generally applied at the species level. It will only be applied independently to cultivars (varieties) or hybrids of a species if there are differences among those cultivars that would result in different responses to the assessment categories. In all cases, the location of a voucher specimen must be identified. (Throughout the assessment, reference to the species under consideration could also refer to a cultivar or hybrid.) For each species, separate conclusions are derived from the assessment for each of three latitudinal zones within Florida. The conclusions include a period after which the species must be reassessed (either 10 or 2 years). However, any species may be reassessed whenever additional relevant information is obtained that changes the results of the assessment. Thus, conclusions might change at any time.

Use of This Assessment Within IFAS

Species will be assessed by trained personnel under the supervision of the IFAS invasive Plant Working Group. The results of each assessment will be made available to all IFAS state and county Extension faculty (hereafter "IFAS faculty") through the web site for the Center for Aquatic and Invasive Plants (http://plants.ifas.ufl.edu/assessment.html ) with links to IFAS Extension web sites. IFAS faculty dealing with non-native plants species in Florida are expected to be familiar with this assessment.

This assessment will place non-native plant species in categories (called index categories). These categories describe varying degrees of Ecological Impacts, Potential for Expansion, Management Difficulty, and Economic Value. Any IFAS Extension publications or newsletters, including those developed by county faculty, that refer to specific non-native plants in relation to the topics covered by this assessment (e.g., invasiveness, ecology, distribution, management, use, recommendations, and value) are required to include a reference to this assessment, and to use the terms and conclusions from the assessment when describing features of these plants. For example, "...shows high ecological impacts such as causing long-term alterations in ecosystem processes and... This species is considered invasive and not recommended by IFAS faculty (Fox et al., 2005)."

This assessment uses the index categories to define "conclusions" about the assessed species, including conclusions such as "Invasive and not recommended by IFAS faculty". Faculty making planting recommendations may choose to include "...not recommended..." plants in their publications, if the conclusions from the assessment are clearly presented. In some situations, it may provide better public education to include a "...not recommended..." plant with the reasons it should be avoided, instead of leaving the species out of the publication entirely. This assessment will be revised periodically, and content and conclusions may change substantially. IFAS Extension publications must conform to the assessment protocol in place at the time of that publication's final drafting, and must be made to conform to the current assessment protocol when that publication is revised. The IFAS Invasive Plants Working Group will continue to review all Extension pre-publications related to invasive plants, and will determine if the direction and intent of these provisions are being followed.

Structure of the Assessment

The assessment is divided into five main sections, one for determining where the plant is invading and the others corresponding to four indices of Ecological Impacts, Potential for Expansion, Difficulty of Management, and Economic Value. These sections are designated by Roman Numerals (I - V). Assessment questions within these sections are located in shadowed boxes which have sub-section letters (I-a, I-b, etc.). Separate questions within a box have their own number which is in either arabic numerals, for questions that influence the order of progression through the assessment (e.g., I-a 1., I-a 2.), or diminutive Roman numerals, for statements to which scores are assigned (e.g., II-a i, II-a ii). Three further sections that directly lead to conclusions have letters A - C and are found at the end of the assessment.

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Certain species, currently existing in Florida or not yet known there, are prohibited by federal or state laws. IFAS faculty will not recommend such species and should note their prohibited status when discussing them. Relevant lists of such species can be found at:

Glossary for this Assessment

Anthropogenic disturbance. Recurring anthropogenic source of soil exposure (e.g., roads, trails, plow lines) and/or vegetation structure change (e.g., mowing) that is not the result of or does not mimic a natural process and that causes partial or total destruction of vegetative biomass. Also includes human-induced changes in natural disturbance regime (e.g., changing the severity of fires; fire suppression in fire-adapted communities or fire in communities not adapted to fire; grazing cattle above the density of native herbivores). In this context, disturbance is likely to facilitate the invasion of rapidly colonizing and persistent species.

Coverage. Visual or quantitative estimate of the relative amount of area in a stratum where the canopy of the non-native species intercepts the light that would otherwise be available for other species in or below that stratum. Estimated cover may be dispersed or continuous in a site. Cover is usually measured when foliage is fully expanded. In the case of species that form a dense, continuous mat of rhizomes or stolons, the percent of the soil surface or upper level occupied by that root mat can be estimated as soil, rather than canopy, cover.

Disturbance. Natural mechanisms that limit biomass by causing its partial or total destruction (e.g., fires caused by lightning; herbivory; flooding; hurricanes).

Discrete populations. A population is a group of individuals of the same species living in the same place and which are much more likely to reproduce with one another than with individuals from another population. For the purposes of this assessment, discrete populations must be at least 1 mile apart. They likely arose by separate, long-distance dispersal events.

Distributional evidence. Search floras, databases, herbaria, etc. (For examples see "Floras, etc." in Other Resources on page 27.) For each relevant record, document: the source (e.g., database, herbarium); the date; the site; the collector; and any other relevant information. If formal documentation is not available, obtain such information (confirmed in writing) from at least two people who have the expertise to identify the particular species.

Documentation of evidence. One publication including relevant, original research will suffice if data are specific to the taxon and zone(s) under evaluation. If such documentation is not available or needs to be up-dated, at least three individuals who have expertise on the particular species and zone in question must be identified. If more than three experts have been identified, use the responses that are most precautionary (i.e., worst assessment of impacts or greatest management needs reported), as consistent with the intent of the assessment. Relevant information (confirmed in writing) must be provided by at least two of the three experts to justify a "yes" response to a question, or to support a score-accruing statement. For example, in Sections II-a and IV, scores are summed for all statements that have each been confirmed either in the literature or by at least two experts. In statement II-a i), if two experts indicate that there have been ecosystem changes 15 points are assigned for this item even if the experts are reporting different types of ecosystem changes. If data in the literature show that a species causes a particular ecological impact but not in the zone under consideration, expert opinion is still needed. However, an expert could give the opinion that this impact is also likely to occur in the zone and that could be one of the three expert opinions needed. Records should be kept of all the experts who were contacted for each species and zone, regardless of whether they provided input.

Federal- or Florida -listed. Species that are listed by Federal laws or Florida statutes or rules as Threatened, Endangered or Species of Special Concern within the State of Florida. The list of endangered and threatened species of plants is available at: http://www.doacs.state.fl.us/pi/enpp/botany/images/Notes2003.pdf

Also species and habitats of special concern that are regulated by Florida Statute include: mangroves (FL statute 403.9321), sea oats and sea grape (FL statute 370.041), cypress trees (FL statute 590.02). Other types of imperiled species are listed at: http://myfwc.com/imperiledspecies/

Invading. A species that forms self-sustaining and expanding populations within a natural plant community with which it had not previously been associated (cf. "invasive" in Vitousek et al. 1995).

Invasive. Invading species that cause documented ecological impacts (> Low: pages 18 - 20).

Long-term alterations in ecosystem processes. Examples of ecosystem processes that could be altered: erosion and sedimentation rates; land elevation; water channels; water-holding capacity; water-table depth; surface flow patterns; rates of nutrient mineralization or immobilization; soil or water chemistry; and type, frequency, intensity, or duration of disturbance. For further explanation see Gordon (1998).

Native. Species within its natural range or natural zone of dispersal (i.e., within the range it could have, or would have, occupied without direct or indirect introduction and/or care by humans. Excludes species descended from domesticated ancestors) (Vitousek et al. 1995).

Natural areas. Areas of Florida (public or private) with designated management objectives that include the conservation of native biodiversity. While a range of activities may be conducted on these areas (e.g., prescribed fire, low intensity grazing), those activities are designed to be compatible with the conservation objective. State and local governments and some private landowners, for example, manage natural areas both for recreation, grazing, forestry or other harvest values and for conservation values. These areas would be included in the assessment of invasion, with clearly identifiable edges disregarded. Species that invade only adjacent to roads, trails, fire lanes, recent dredge spoil, formerly cultivated areas, expanses of bare soil, etc. should not be identified as invaders with impacts in natural areas because their persistence and spread is only in these clearly anthropogenically disturbed zones in the natural area. Populations of species that spread along these disturbed zones but disperse over 10 yards into more intact natural areas would be included as invading. Ecological impacts would be assessed only where the population has spread into the intact natural areas and not within the source population in the disturbed or formerly cultivated area.

Pollen or genetic invasion. When a native species is displaced by a non-native species through hybridization.

Sites. Locations that can be distinctly described by name (e.g., named State Park or lake) and may be subdivided into distinct habitats and/or communities (e.g., mesic uplands in Acme Park and rocklands in Acme Park). A site may contain more than one discrete population of a species provided that the populations are at least 1 mile apart.

Stratum. A distinct layer in the architecture of vegetation (e.g., tree canopy, under-story shrubs).

References

Gordon, D.R. 1998. Effects of invasive, non-indigenous plant species on ecosystem processes: lessons from Florida. Ecological Applications 8: 975-989.

Vitousek, P., L. Loope, C. D'Antonio and S.J. Hassol. 1995. Biological invasions as global change. pp. 213-336 In: S.J. Hassol and J. Katzenberger (eds) Elements of change 1994. Aspen Global Change Institute, Aspen, CO.

Other Resources

Floras, databases, herbaria, etc.

Plant locators

Footnotes

1. This document is SS-AGR-225, one of a series of the Agronomy Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Revised June 2005. Visit the EDIS Web Site at http://edis.ifas.ufl.edu.

2. Alison M. Fox, associate professor, Agronomy Department, University of Florida, Gainesville, FL; Doria R. Gordon, state ecologist, The Nature Conservancy and courtesy professor, Department of Botany, University of Florida, Gainesville, FL; Joan A. Dusky, professor and associate dean for Extension, University of Florida, Gainesville, FL; Linda Tyson, professor, Santa Fe Community College, Gainesville, FL; and Randall K. Stocker, professor, Agronomy Department, University of Florida, Gainesville, FL. Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL.

The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication does not signify our approval to the exclusion of other products of suitable composition.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other extension publications, contact your county Cooperative Extension service.

U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Larry Arrington, Dean.


Copyright Information

This document is copyrighted by the University of Florida, Institute of Food and Agricultural Sciences (UF/IFAS) for the people of the State of Florida. UF/IFAS retains all rights under all conventions, but permits free reproduction by all agents and offices of the Cooperative Extension Service and the people of the State of Florida. Permission is granted to others to use these materials in part or in full for educational purposes, provided that full credit is given to the UF/IFAS, citing the publication, its source, and date of publication.