Maps of Occupation and Estimates of Acres Covered by
Nonnative Invasive Plants in Southern Forests


James H. Miller, Research Invasive Ecologist
and
Erwin B. Chambliss, Research Associate
USDA Forest Service Southern Research Station
Auburn, Alabama

and
Christopher M. Oswalt
USDA Forest Service Southern Research Station
Forest Inventory and Analysis
Knoxville, Tennessee

Maps of occupation and tabular coverage estimates are accessible for 33 recognized nonnative plants invading forests of the 13 southern States using U.S. Forest Service's Southern Research Station Forest Inventory and Analysis (SRS FIA) data posted as of March 15, 2008. Links and instructions are also provided for how you can access, view summary tables, and download the most current data for these species and 20 other nonnative plants invading Florida.

These maps and data are made available as tools to focus State, county, agency, and individual's invasive plant management programs and to gain greater support. Just as important, the web database can be used to determine the current occupation and model future spread, costs, and impacts to forest-human ecosystems by researchers and agencies.

Summary of the Information and Data Links

  • Regional Maps of the invasive plant species by:
    • Percent of subplots in a county occupied by each nonnative invasive plant species (NIPS) or species group (genera).
    • Acres in a county covered by each NIPS or species group.
  • Estimated acres covered by the 33 nonnative invasive plants species in a State and the Southern Region
  • Details of the Survey and How to access and view the data.

Regional Maps of Invasive Plant Species

Two sets of maps have been produced using data posted at "Nonnative Invasive Plant data tool", http://srsfia2.fs.fed.us/nonnative_invasive/Southern_Nonnative_Invasives.htm on March 15, 2008. Up to seven years of data had been collected for some States and preliminarily verified, released by the States' Forester, and posted. A map of the number of subplots surveyed in a county at that date can be viewed at Subplots per County.

The two map sets can be accessed here:

Estimates of Acres Covered

A spreadsheet of cover estimates by species within each State and the totals for the USDA Forest Service's Southern Region has been produced using the database from March 15, 2008. Mid-point values for each cover category have been summed for all the sub-plots containing the NIPS in a county and multiplied by 1,500 acres. This expansion factor is the regional mean for all the sampling proportion of all subplots. The county estimates were then summed to gain the State and regional estimates.

The recommended citation for the maps and cover estimates is:
Miller, James H.; Chambliss, Erwin B; Oswalt, Christopher M. 2008. Maps of occupation and estimates of acres covered by nonnative invasive plants in southern forests using SRS FIA data posted on March 15, 2008. [Available only on the internet: http://www.invasive.org/fiamaps/ Date accessed: Month-day-year]

Details of the Survey

USDA Forest Service Research in partnership with State forestry agencies initiated a Southern Region survey of 33 invasive plant taxa in 2001 on all forest ownerships. The survey of invasive plant species was added to the traditional timber resource surveys that have been underway since the 1930's, commonly referred to the Southern Forest Inventory and Analysis.

The Nonnative Invasive Plant Species (NNIPS) selected for survey were regionally recognized exotic pest plants known to invade interior forest stands and forest edges, gaps and stream-sides less than 120 feet wide. Plants surveyed in all States in the Southern Region are:

Invasive Trees: tree-of-heaven (Ailanthus altissima), silktree or mimosa (Albizia julbrissin), princesstree or paulownia (Paulownia tomentosa), chinaberrytree (Melia azedarach), tallowtree or popcorntree (Triadica sebifera), and Russian olive (Elaeagnus angustifolia).

Invasive Shrubs: silverthorn (Elaeagnus pungens), autumn olive (Elaeagnus umbellata), winged burning bush (Euonymus alatus), Chinese and European privets (Ligustrum sinense and L. vulgare), Japanese and glossy privets (Ligustrum japonicum and L. lucidum), nonnative bush honeysuckles (Lonicera maackii, L. morrowii, L., tartarica, L. fragrantissima, and L. xbella), nandina (Nandina domestica), and nonnative roses (Rosa multifora, R. bracteata, and R. laevigata).

Invasive Vines: oriental bittersweet (Celastrus orbiculatus), nonnative climbing yams (Dioscorea oppositifolia and D. bulbifera), wintercreeper (Euonymus fortunei), English ivy (Hedera helix), Japanese honeysuckle (Lonicera japonica), kudzu (Pueraria montana), vincas or periwinkles (Vinca minor and V. major), nonnative wisterias (Wisteria sinensis and W. floribunda).

Invasive Grasses and Canes: giant reed (Arundo donax), tall fescue (Lolium arundinaceum), cogongrass (Imperata cylindrica), Nepalese browntop or microstegium (Microstegium vimineum), Chinese silvergrass (Miscanthus sinensis), and nonnative bamboos (Phyllostachys aurea and other Phyllostachys spp. and Bambusa spp.).

Invasive Fern and Forbs (broadleaved plants): Japanese climbing fern (Lygodium japonicum), garlic mustard (Alliaria petiolata), shrubby lespedeza (Lespedeza bicolor), Chinese lespedeza (Lespedeza cuneata), and tropical soda apple (Solanum viarium).

The manual used by the surveyors, "Nonnative Invasive Plants in Southern Forests: a Field Guide for Identification and Control" is accessible at: http://www.srs.fs.usda.gov/pubs/gtr/gtr_srs062/

And a HTML format at http://www.invasive.org/eastern/srs/

Copies can be ordered via email (pubrequest@fs.fed.us), phone (828-257-4830), or mail (Southern Research Station, 200 W.T. Weaver Boulevard, Asheville, NC 28804-3454).

Each State inventory commenced in different years and have varying rates of cycle completions (entire State) while at least one-fifth of the plots within a State are expected to be inventoried every year (one "Panel"). This is an ongoing process. States have progressed at different rates and are tracked by cycle, panel, and year. State inventory histories and current progress can be viewed at http://srsfia1.fia.srs.fs.fed.us/data_center/index.shtml. The Oklahoma inventory is being updated currently and the results should be available in early 2009. As time progresses more current inventory data will be added to the data base.

Percent cover by species is recorded on four permanent subplot clusters of 1/24 acre each located across forested landscapes on an approximately 3-mile grid. Each subplot represents about 1,500 acres. Cover is currently recorded by five category codes: 1 = Trace < 01%; 2 = 01-10%; 3 = 11-50%; 4 = 51-90%; and 5 = 91-100%. Mid-point values for each category have been used to calculate an estimate of cover by species for each State and a total for the Region. FIA plots sample only a small fraction of forest land, and samples are located systematically at widely-spaced intervals, so species that are regionally common are more likely to be recorded and cover estimates will be more precise. Species that are locally abundant but widely scattered, or that occur infrequently, will be estimated with less precision.

How to access and view the data

To access data and view summaries on the current distribution of the 33 invasive plants covered in Nonnative Invasive Plants of Southern Forests and the additional 20 forest invasive plants in Florida, go to the following website and follow the appropriate links.

Southern Research Station Forest Inventory and Analysis (FIA) Data Center at: http://srsfia2.fs.fed.us/data_center/index.shtml

For the invasive plant data click on - "Nonnative Invasive Plant data tool" or go directly to: http://srsfia2.fs.fed.us/nonnative_invasive/Southern_Nonnative_Invasives.htm

At this website is an overview of the survey methods used to collect the data with the documented changes in procedures and any noted discrepancies. The data are summarized in separate tables for invasive trees, shrubs, vines, grasses, and ferns/forbs.

This data access tool allows the user to:

  • View the Plant Profile description on USDA Plants Database by clicking on the species name on the table header.
  • Have the data displayed for that State by counties by clicking on the State name in the first column.
  • Find all the FIA State and county data for that species by clicking on the species total at the bottom of the table.
  • Save the data by right clicking and export to Excel™ worksheet to create summaries or perform analyses. The Excel™ worksheet also can be saved as a .DBF™ file to import into ArcView™ or other mapping programs.
  • Merge the invasive plant data with other publicly available FIA data - details are on the website listed above.

For those already familiar with other FIA data, exploratory research may be conducted by downloading the NNIPS information and linking it with associated FIA data that resides on the FIA DataMart website http://www.ncrs2.fs.fed.us/FIADatamart/fiadatamart.aspx. The data available for download from the FIADB/Mapmaker website has coordinates and ownership values "fuzzed and swapped" to approximate locations recognizing privacy rights. To better understand this issue, please see this website and contact SRS FIA for clarification and assistance. You can use the link at "contact us."

Remember that these data have been taken on forested plots including a small proportion of forest edges. No observations have been recorded for invasive plant species that occur on non-forested lands. Invasive species that are rare on forest land but abundant on non-forest land may not be recorded by the FIA sampling scheme.

Results yield estimates of relative abundance, range, and impacted area on forest land, while long term monitoring is to assess the rate of spread. These regional data are for strategic resource assessments on forest land, and for planning control and management programs. Geographically-referenced observations from non-forest lands are necessary to complete a strategic assessment on all land areas. Currently, forestland modeling can be developed through analysis of overstory tree and plot attributes, and landscape context information from other sources.

Efforts are continually underway to document discrepancies in the data using quality assurance and accuracy checks by the SRS FIA staff. Discrepancies such as misidentifications that have been noted and the changes made are posted at the top of the data summary tables for a period. The most current data posted for a State is also noted at this location until further posting are made. If you find other discrepancies or have suggestions for improving the website and data summaries please convey these to SRS FIA customer service representatives or through the contact us link.

The recommended citation for this web application is:
Ridley, Ted; Rudis, Victor A.; Beresford, Helen. Forest inventory nonnative invasive plant web-application, version 1.0. Knoxville, TN: U.S. Department of Agriculture, Forest Service, Southern Research Station, Forest Inventory and Analysis Program.
[Available only on the internet: http://srsfia2.fs.fed.us/nonnative_invasive/Southern_Nonnative_Invasives.htm
Date accessed: Month-day-year].

A comprehensive list of all plants that are considered to be invasive in the Southern Region can be viewed at http://www.invasive.org/south/, which may be useful for constructing prevention and control strategies. Much more helpful information on invasive species identification and control is accessible at this website.

Acknowledgement: The SRS FIA Invasive Plant Coordinator during the initiation and formative phase of the project was the late Dr. Victor A. Rudis. He made major contributions to the selection of species for inventory, the inventory protocols, accuracy of data, and construction of the innovative web portal. He was relentless in his many efforts to aid our region in recognizing and managing the invasion of southern forests by nonnative plants. Without his insightful guidance and persistence, these data and data summaries would not be available for our continued struggle to save our forests.


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