Managing Invasive Plants: Concepts, Principles, and Practices link

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MANAGING INVASIVE PLANTS: Concepts, Principles, and Practices

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Review, Resources, & References


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Key Points


Knowledge gained from assessments can provide a deeper understanding of the problems and solutions associated with plant invasions so that land managers are better equipped to identify management strategies and options, establish action thresholds and measurable management objectives, select safe and effective management methods, and evaluate program outcomes.


Invasive plant management is essentially a form of risk management, where invasive plants or the methods used to control them may present a threat (risk) to a valued resource. Risks (likelihood and consequences) of plant invasions and their management are highly variable and not fully understood. Managing risk requires a thorough understanding of the problem (invasive plants) and solutions (management actions).


Assessment systems have been devised for characterizing plant species in terms of their invasiveness, impacts, and feasibility of control (ranking systems); and for characterizing areas in terms of their ecological value or vulnerability to invasion (geospatial analysis). Together, these systems can help prioritize prevention and control efforts to specific areas and invasive plant populations.


Action thresholds are helpful in prioritizing and selecting management strategies and options. Management objectives that describe desired invasive plant population levels in specific measurable terms may help define action thresholds in some situations. Monitoring is used to measure population changes over time and detect progress towards or away from desired action thresholds and management objectives.


Assessments can help identify appropriate management strategies (prevention, detection, control, restoration) by characterizing the phase of the plant invasion process (introduction, colonization, naturalization) for populations. Assessments also help to prioritize populations for eradication, suppression, and/or containment.


Inventories and surveys are both conducted to acquire information about the location and/or abundance of a resource at one point in time. Inventories catalogue species within an entire area, whereas surveys sample a representative portion of an area. Mapping is one way to gather, record, depict, or communicate inventory or survey information. Monitoring is a survey repeated through time to determine changes in the status and trends of a resource.


Inventories and surveys generally fall into two different types based on their overall purpose: those that document the distribution and abundance or invasive plant populations for making management decisions; and those that attempt to further understanding of invasive plant populations or plant communities.


There are several types of invasive plant monitoring that may be employed depending on information needs and land management goals: early detection, effect of management action on target invasive plant populations or nontarget species and the environment, status and trends of target species populations, and effect of invasive plants on native species and the environment.


A monitoring plan provides the blueprint to reach invasive plant management objectives and facilitates continuity in the program from implementation, to evaluation, to adapting management if needed. This plan may be integrated into other planning documents.


Prior to initiating an assessment it is important to consider the overall goals and objectives of the assessment, the scale and scope, the type and detail of data to be used, and methods for collecting and analyzing data and making decisions. While assessments should be conducted in a way that provides sufficient information and understanding to make sound decisions that support management goals, it is important to conduct the best assessment possible within a reasonable timeframe and budget.

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Risk Assessment and Management

Information Resources for Weed Risk Assessment

US Environmental Protection Agency - Guidelines for Ecological Risk Assessment

Alien Plants Ranking System - Version 5.1

National Park Service - Handbook for Ranking Exotic Plants for Management and Control

Australia Weed Risk Assessment System

National Invasive Species Information Center

Invasive Plant Management: CIPM Online Textbook

US Forest Service Rocky Mountain Research Station - Simulating Patterns and Processes at Landscape Scales

Society for Ecological Restoration International - Reading Resources

Hazard Analysis and Critical Control Points Plan

USDA Forest Service Invasive Species Prevention

Invasive Species: Manager's Tool Kit - Prevention

Center for Invasive Plant Management - Invasive Plant Prevention Guidelines

A National Early Detection and Rapid Response System for Invasive Plants in the United States (3.4 MB PDF)

Early Detection of Invasive Plant Species Handbook


Measuring and Monitoring Plant Populations (Elzinga et al. 1998) (5.13 MB PDF)

Inventory and Survey Methods for Nonindigenous Plant Species

L Rew, ML Pokorny, editors. 2006. Bozeman (MT): Montana State University Extension. 75 p.

North American Weed Management Association - North American Invasive Plant Mapping Standards
(250 KB PDF)

US Fish and Wildlife Service NWR Volunteer Weed Mapping Manual
(3.3 MB PDF)

The Nature Conservancy - Weed Information Management System

The Nature Conservancy - Remote Sensing: A Primer

US Forest Service - A Weed Manager's Guide to Remote Sensing and GIS

National Biological Information Infrastructure - Early Detection and Rapid Response

US Geological Survey National Institute of Invasive Species Science - Gather Survey Data

US Geological Survey & National Park Service - Early Detection of Invasive Species Handbook


Measuring and Monitoring Plant Populations (Elzinga et al. 1998) (5.13 MB PDF)

National Park Service Vital Signs Monitoring

Natural Resources Monitoring Partnership

US Geological Survey National Institute of Invasive Species Science

US Geological Survey & National Park Service - Early Detection of Invasive Species Handbook

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Anderson DG, Lavender A. 2006. Noxious Weed Monitoring at the US Air Force Academy - Year 1 Results. Fort Collins (CO): Colorado Natural Heritage Program. 35 p.

Andersen KA, Dewey SA. 2007. USU Wildland Weed Mapping Methods Training Supplement. Master thesis. Logan (UT): Utah State University. 107 p.

APHIS. 2004. USDA Animal and Plant Health Inspection Service. Weed-initiated Pest Risk Assessment Guidelines for Qualitative Assessments. (771 KB PDF) < plant_health/plant_pest_info/weeds/downloads/wra.pdf>. Accessed 2007 Oct 30.

APRS Implementation Team. 2001. Alien Plants Ranking System. Southwest Exotic Plant Information Clearinghouse. <>. Accessed 2007 Oct 30.

Barnett DT, Stohlgren TJ, Jarnevich CS, Chong GW, Ericson JA, Davern TR, Simonson SE. 2007. The art and science of weed mapping. Environmental Monitoring and Assessment 132:235-252.

Barnett DT, Stohlgren TJ, Lusk M, Ericson JA. 2005. Iterative Sampling of Non-native Plant Species at Hart Mountain National Antelope Refuge.

Briske DD, Fuhlendorf SD, Smeins FE. 2006. A unified framework for assessment and application of ecological thresholds. Rangeland Ecological Management 59:225-236.

Brown JR, Herrick J, Price D. 1999. Managing low-output agroecosystems sustainably: the importance of ecological thresholds. Canadian Journal of Forestry Research 29:1112-1119.

Cal-IPC. 2006. California Invasive Plant Council. California Invasive Plant Inventory. (1.89 MB PDF)<>. Accessed 2007 Oct 30.

Chippendale JF. 1991. Potential returns to research on rubber vine (Cryptostegia grandiflora). Master Thesis. Brisbane (QLD): University of Queensland.

Coble HD, Mortensen DA. 1991. The threshold concept and its application to weed science. Weed Technology 6:191-195.

Cousens R and Mortimer M. 1995. Dynamics of Weed Populations. New York:Cambridge University Press. p 21.54

Elzinga CL, Salzer DW, Willoughby JW. 1998. Measuring and Monitoring Plant Populations. Denver (CO): US Department of Interior, Bureau of Land Management, Report #BLM/RS/ST- 98/005+1730. (5.13 MB PDF) <>. Accessed 2007 Oct 30.

Endress BA, Radosevich SR, Naylor BJ, Wells J, Parks CG. 2006. Beyond inventory/survey and monitoring: risk assessment and management. In: Rew LJ, Pokorny ML, editors. Inventory and Survey Methods for Nonindigenous Plant Species. Bozeman (MT): Montana State University Extension. p 70-74.

EPA. 1998. US Environmental Protection Agency. Framework for Ecological Risk Assessment. (1.16 MB PDF) <>. Accessed 2007 Oct 30.

Hiebert R. 2001. Prioritizing weeds: the alien plant ranking system. Conservation in Practice 2(1):36-38.

Hiebert R. 1997. Prioritizing invasive plants and planning for management. In. Luken JO, Thieret JW, editors. Assessment and Management of Plant Invasions. New York (NY): Springer-Verlag. p 195-212.

Hiebert R, Stubbendiek J. 1993. Handbook for Ranking Exotic Plants for Management and Control. US National Park Service Natural Resources Report NPS/NRMWRO/NRR-93/08.

Hobbs RJ, Humphries SE. 1995. An integrated approach to the ecology and management of plant invasions. Conservation Biology 9(4):761-770.

Hogle I, Spenst R, Leininger S, Block G. 2007. San Pablo Bay National Wildlife Refuge Lepidium latifolium Control Plan. Petaluma (CA): US Fish and Wildlife Service, San Pablo Bay National Wildlife Refuge.

Kuchler AW. 1988. General considerations. In: Kuchler AW, Zonneveld IS, editors. Vegetation Mapping, Handbook of Vegetation Science, Vol 10. Boston (MA): Kluwer Academic Publishers. p 191-202.

Mantas M, The Nature Conservancy of Montana, Northern Region Cohesive Strategy Team, Flathead National Forest. 2003. Evaluating Risk to Native Plant Communities from Selected Exotic Plant Species. <>. Accessed 2007 Oct 30.

Martin B, Hanna D, Korb N, Frid L. 2007. Decision Analysis of Alternative Invasive Weed Management Strategies for Three Montana Landscapes. Prepared by the Nature Conservancy of Montana, Helena, MT and ESSA Technologies Ltd., Vancouver BC, 34 p. <http://conserveonline. org/docs/2007/02/MT_invasives_2-15-2007.pdf>. Accessed 2007 Oct 10.

Morse LE, Randall JM, Benton N, Hiebert R, and Lu S. 2004. An Invasive Species Assessment Protocol: Evaluating Non-Native Plants for Their Impact on Biodiversity. Version 1. NatureServe, Arlington, Virginia. (873 KB PDF) < invasiveSpeciesAssessmentProtocol.pdf>. Accessed 2007 Oct 30.

National Research Council. 2002. Predicting Invasions of Nonindigenous Plants and Plant Pests. Washington DC: National Academy Press. p 194.

NAWMA. 2002. North American Weed Management Association. North American Invasive Plant Mapping Standards. (251 KB PDF) <
>. Accessed 2007 Oct 30.

Pheloung PC, Williams PA, Hallow SR. 1999. A weed risk assessment model for use as a biosecurity tool evaluating plant introductions. Journal of Enviromental Management 57:239-251.

Pokorny ML, Dewey SA, Radosevich SR. 2006. Getting started: fundamentals of nonindigenous plant species inventory/survey. In: Rew LJ, Pokorny ML, editors. Inventory and Survey Methods for Nonindigenous Plant Species. Bozeman (MT): Montana State University Extension. p 8-16.

Radosevich S. Online textbook chapter 3: Plant invasions and their management. Center for Invasive Plant Management. <>. Accessed 2007 October 30.

Repath CF. 2005. Evaluating and Monitoring Invasive Plant Processes. Master thesis. Bozeman (MT): Montana State University. 130 p.

Rew LJ, Maxwell BD, Aspinall R. 2005. Predicting the occurrence of nonindigenous species using environmental and remotely sensed data. Weed Science 53(2):236-241.

Rice PM. 2007. INVADERS Database System: Risk Assessment for Potentially Noxious Species in Idaho and Montana. Division of Biological Sciences, University of Montana, Missoula. <>. Accessed 2007 October 30.

Schnase JL, Smith JA, Stohlgren TJ, Graves S, Trees C. 2002. Biological invasions: a challenge in ecological forecasting. In: Proceedings of Geoscience and Remote Sensing Symposium, 2002 (IGARSS ‘02. Toronto), IEEE 2002 International Vol. 1, p 122-124.

Shafii B, Price WJ, Prather GS, Lass LW, Thill DC. 2003. Predicting the likelihood of yellow starthistle (Centaurea solstitialis) occurrence using landscape characteristics. Weed Science 51:748-751.

Stohlgren TJ, Chong GW, Schell LD, Rimar KA, Otsuki Y, Lee M, Kalkhan MA, Villa CA. 2002. Assessing vulnerability to invasion by nonnative plant species at multiple spatial scales. Environmental Management 29(4):566-577.

Stohlgren TJ, Schnase JL. 2006. Risk analysis for biological hazards: what we need to know about invasive species. Risk Analysis 26(1):163-173.

Suedel BC, Bridges TS, Kim J, Payne BS, Miller AC. 2007. Application of risk assessment and decision analysis to aquatic nuisance species. Integrated Environmental Assessment and Management 3(1):79-89.

Taylor JD. 2004. Surveying and mapping invasive plants on Northeast refuges. In: Hales S, Mars S, Popolizio C, Robinson S, Stern C. US Fish & Wildlife Service Field Notes, New Jersey Field Office, Spring 2004. <>. Accessed 2007 Oct 31.

US Fish and Wildlife Service. 2006. National Wildlife Refuge Volunteer Weed Mapping Manual. (3.3 MB PDF) <>. Accessed 2007 Oct 30.

Williams BK, Szaro RC, Shapiro CD. 2007. Adaptive Management: The US Department of the Interior Technical Guide. Adaptive Management Working Group, US Department of the Interior, Washington, DC. (36 MB PDF) <>. Accessed 2007 October 31.

Wootton L, Georgian Court University. Asiatic Sand Sedge Carex kobomugi. <>. Accessed 2007 Oct 30.