Inventory and Survey Methods for Nonindigenous Plant Species (PDF)

Chapter 9 • Coarse-Scale Mapping: The Section or Quadrangle-based MethodSection Based Map of Phillips County, MT▲ Figure 1. Example of a blank section-based map ofPhillips County, MT. Data would be filled in for leafy spurge bythe weed coordinator for Phillips County (after Powell CountyQuarter-Section Based Mapping Project, Jason Smith, WeedCoordinator).mapping links the spatial unit (for example, square-milesections) to a table that identifies whether an NIS is present,absent, or unknown in that entire unit. Spatial layers thatform the framework of coarse-scale mapping are availablefor download from digital GIS data clearinghouses on theInternet. For example, the Section Based Weed MappingProject implemented by the MDA uses several spatial layersavailable from the online digital library of the NRIS (http://nris.state.mt.us/), including PLSS sections and townships,county boundaries, highways, railroads, towns, and rivers.Powell County Weed District includes weed managementarea boundaries on their quarter-section maps. Theseadditional layers provide a spatial reference for each section’slocation.County Level ExamplesThe NIS attributes are populated in the database tableassociated with the PLSS section. The NIS attribute cansimply denote whether the species is present, absent, orstatus unknown in the given section, or the attribute canbe assigned a category based on estimated number of acresinfested in the unit. For example, Powell County uses thefollowing categories: absent (no NIS), low (less than 8 acres),moderate (8 to 40 acres), and high (more than 40 acres)for each quarter section (160 acres). These attribute valuesprovide a more accurate estimate of the acres infested.Coarse-scale mapping takes advantage of the knowledgeof landowners and land managers familiar with locallandscapes. The utilization of local knowledge and directexperience is called knowledge-based mapping. Hard copymaps detailing each mapping unit (i.e., quarter-sections,sections, or quarter-quadrangles) are created and distributedto county weed coordinators if mapping at the statewidelevel, or to private landowners and state and federal landmanagers if mapping at the county level.Examples of how coarse-scale maps are created areprovided for Phillips and Powell counties in Montana. Inboth cases landowners participate to some extent withthe data input into the map. In Phillips County, the weedcoordinator receives a map that depicts each section withinthe county (landscape features such as roads and streamsmake identifying infested areas easier as well), and thenrecords, for example, the status of leafy spurge (Euphorbiaesula) in the sections where the information is known(Figure 1). The coordinator then consults with local landmanagers to fill in the knowledge gaps. If nothing is knownabout a particular section, the leafy spurge status is left asunknown, or changed to present or absent if knowledge isavailable. Completed maps for all noxious weed species arereturned to the statewide mapping coordinator so a GISspecialist can compile data and generate final maps. Analternative approach is used by the Powell County weedcoordinator who sends a quarter-section map for NIS ofinterest to each landowner participating in a cooperativeweed management area in the county. Landowners fill inthe target NIS information for their property and return themap to the weed coordinator. The county then compilesthe information and can update the county-wide NIS maps.The compiled county data can easily be submitted to thestatewide database.State Level ExamplesIn Montana, the MDA and NRIS have designed a mappingapplication that enables county weed coordinators and otherNIS managers to enter NIS location information interactivelythrough the Internet. Weed managers with restricted access66Inventory and Survey Methods for Nonindigenous Plant Species