Inventory and Survey Methods for Nonindigenous Plant Species (PDF)

Beyond Inventory/Survey and Monitoring:Risk Assessment and ManagementChapter 10Bryan A. Endress, Steven R. Radosevich, Bridgett J. Naylor, John Wells, andCatherine G. ParksIntroductionAnticipating species that will become invasive andknowing where to look for them is a critical aspectof nonindigenous plant management. Managersand policy makers alike want to know the likelihoodthat new nonindigenous species (NIS) will becomeprevalent over large areas, as well as which habitatsand ecosystems are at risk of invasion. Although NISinventory/survey and monitoring activities are critical todeveloping effective NIS management programs, theyare limited in their ability to predict the likelihood offuture invasions by different species. Thus, ecologistsgenerally have been able to provide only after-the-factexplanations for NIS invasions. Risk assessments,like those currently employed by state and federal landmanagement agencies to assess wildfire risks, are anemerging tool to assess the risk of NIS establishmentand spread. Here we introduce the concept of nonindigenousplant species risk assessment and providean example of an ongoing project in northeast Oregon.Additionally, potential benefits to land managers andcurrent challenges to the development of usable,effective, on-the-ground NIS risk assessments arediscussed.What Is an NIS Risk Assessment?The primary objective of an NIS risk assessment is toserve as a proactive tool for land managers and policy makersthat (1) evaluates the likelihood of NIS establishmentand spread, (2) identifies which species pose the greatestthreat in a particular area or landscape, and (3) highlightsareas at greatest risk to certain NIS. The information canthen be used to prioritize management actions, includingNIS inventory/survey, monitoring, prevention, control, andrestoration activities.Risk assessments generally include information on (1)ecological and environmental characteristics of an area, suchas vegetation, land use, disturbance history, slope, elevation,and soil; (2) biological information on particular NIS, suchas their habitat requirements and spread rates; and (3)locations of NIS taken from patch observations. This informationcan be combined using a geographic informationsystem (GIS) so that areas can then be classified or rankedon their “invasability” or degree of risk to NIS invasions.How Is an NIS Risk AssessmentPlanned and Conducted?In 2002, we began developing a prototype NIS riskassessment model. The study objectives were to assess thefeasibility of creating effective risk models using existingdata from the USDA Forest Service, and to identify challengeslimiting their development and use. The StarkeyExperimental Forest and Range (SEFR), located in the BlueMountains of northeastern Oregon, was chosen as theinitial study area because of its manageable size (77.6 km 2 ,or 19,180 acres), diverse landscape of forest and grasslandcommunities, and the availability of a GIS database forthe area. Elevations in SEFR range from 1,122 to 1,500 m(3,681 to 4,921 ft), and dominant plant communities includemixed conifer and ponderosa pine (Pinus ponderosa) forests,as well as grasslands dominated by bluebunch wheatgrass(Pseudoroegneria spicata). Here we outline the process ofconducting an NIS risk assessment by focusing on one NIS,sulfur cinquefoil (Potentilla recta).In 2003, after sulfur cinquefoil was initially found in SEFRduring an NIS inventory, we wanted to assess the risk of itsfurther spread within SEFR. Sulfur cinquefoil can invadeand dominate a variety of vegetation types (see Rice 1999;Zouhar 2003; and Endress and Parks 2004 for summariesof sulfur cinquefoil ecology and management). Roadsides,abandoned agricultural fields, clear-cuts, and other disturbedsites are particularly susceptible to invasion by thisplant species. Additionally, low-disturbance sites, includingnative bunchgrass communities, ponderosa pine stands, andopen-canopied mixed-conifer forests, are also susceptible.Sulfur cinquefoil can pose a serious threat in many areas ofthe Blue Mountains ecoregion due to its prolific seed production.When plant communities become infested with sulfurcinquefoil it is believed that native plant diversity decreasesand natural ecosystem processes are altered (Rice 1999).To determine areas at risk to sulfur cinquefoil invasionand to produce a risk map for SEFR, we considered threefactors: (1) the susceptibility of existing plant communitiesto invasion, (2) disturbance history, and (3) the proximity tocurrent infestations.SusceptibilitySusceptibility is the vulnerability of plant communities inSEFR to the establishment of sulfur cinquefoil. To determinesusceptibility we collected sulfur cinquefoil occurrenceinformation from state, federal, and private organizationswithin the Blue Mountains ecoregion (including Wallowa,Union, Umatilla, and Baker counties) and combined thisinformation with existing vegetation information in GIS. Thecombined data verified which plant communities within the70Inventory and Survey Methods for Nonindigenous Plant Species