Inventory and Survey Methods for Nonindigenous Plant Species (PDF)

Chapter 1 • Getting Startedof large NIS infestations and to locate all isolated patchesdiscovered beyond the main infestation. Reconnaissanceinventories/surveys should be conducted periodically inorder to detect new patches before any become too largeto eradicate. Reconnaissance inventories/surveys can belimited to specific areas considered most susceptible tonew NIS introductions and/or establishment (roads, trails,campgrounds, etc.), or they may be performed over theentire area. Typically, little effort is devoted to locating anddelineating large infestations of species already known tobe abundant. This allows for faster coverage of targetedareas and ensures that a maximum number of acres can besearched for new patches or new species within the allottedtime and budget. Reconnaissance inventories/surveys mayinvolve searches over several hundred to many thousandsof acres. Little if any additional data are collected beyondspecies, location, and size of patches. It may be reasonable tocombine exploratory and reconnaissance inventory/surveyinto a single field operation. Map scale is typically 1:24,000or finer.ExtensiveIn general, extensive inventory/survey should not beconducted until after an exploratory and/or reconnaissanceproject has been completed. Extensive inventory/survey mayinvolve relatively large tracts of land, much like the exploratoryor reconnaissance categories. However, the objective ofextensive inventory/survey is to collect data that are considerablymore detailed, more accurately delineated, and/orat a finer resolution than those collected by exploratoryinventories/surveys, in order to build upon and refine datagathered previously. One of the biggest differences betweenextensive inventory/survey and the previous two categoriesis that in an extensive inventory/survey data on indigenousspecies are also collected to study possible correlations orassociations between NIS, native vegetation, and/or certainenvironmental factors. Extensive inventory/survey is generallymore expensive than exploratory or reconnaissancetypes. Requirements for greater detection resolution and/orthe collection of the additional data generally result in feweracres being inventoried or surveyed per day. An extensiveinventory/survey is almost always conducted at a finer scalethan the exploratory or reconnaissance types, at a map scaleof 1:24,000 or finer.IntensiveThe objective of intensive inventories/surveys is to obtainas much information as possible about NIS, other plantspecies, and environmental factors at a level of accuracy anddetail sufficient to allow meaningful scientific interpretationsof ecological relationships. According to Kuchler’sdefinition, an intensive inventory/survey usually implies arelatively small area, perhaps a few hundred acres or less,but may require the same amount of time and expense as amuch larger area inventoried/surveyed extensively (Kuchlerand Zonneveld 1988). Inventories/surveys are consideredintensive if locating individual NIS and characterizing theplant communities in which they are found are the majorobjectives of the project effort. Observers attempt to reducethe degree of generalization to a minimum by recordingevery detail of the NIS community structure, including otherplant species. Intensive inventories/surveys may include collectionof data on phenology, floristic composition, dynamicfeatures, land use, elevation, relief, slope, exposure, soil,water, or geologic character. The level of detail involved infine-scale inventories/surveys may make some of the collecteddata useful as a baseline for future monitoring projects.For example, with improved statistical analysis and modelingit is now possible to sample intensively over a relativelysmall area and predict the occurrence of the target NIS overa much larger management area which was not sampled.Intensive maps are often at scales of 1:5,000 to 1:1,000.Sampling NIS in the LandscapeNonindigenous plant inventories and surveys are used tolocate plant populations and then record and/or delineate theirlocation. Some fundamental techniques for sampling NIS andtheir advantages and disadvantages are discussed below.Sampling DesignOnce managers have identified their NIS managementand inventory objectives—what NIS they want to searchfor, where, and why—they need to determine the inventory/survey sampling design for the landscape of interest.Nonindigenous plant location data are generally collectedusing point, transect, and swath (or band) sampling unitsin the landscape. Point sampling units are usually circular,transect and swath sampling units are linear and dataare collected continuously, and unit size is predefined inall cases. In transect sampling, NIS can be inventoried/surveyed directly below a transect line or for a designateddistance on either side of the transect line. Transects areoften sampled in straight lines, and if reproducibility isdesired, they may have a marked beginning and end. Swathssample the management area in bands of land. The widthof the swath is a predetermined distance on both sides ofthe surveyor (e.g., 25 to 100 m), and the length of the swathvaries. Swaths are often not straight and the route is notalways meant to be reproducible. Transects and swaths canalso be established as designated routes of travel in whichdata (i.e., NIS presence) are collected as points along theroute, potentially at randomly determined locations.12Inventory and Survey Methods for Nonindigenous Plant Species