Inventory and Survey Methods for Nonindigenous Plant Species (PDF)

Chapter 3 • Landscape-Scale Wildland Inventoriesq Figure 2. Daily inventory routes of each crew member were recorded and mapped within the project area (black line) using thebetween feature points (BFP, black points) tracking function of the GeoExplorer GPS units. Here BFP were taken every 500 ft (152m) to show that a surveyor had been in an area even if no NIS locations were recorded.maintain confidence that at least 90% of all infestations oftarget species 0.01 acre or larger within the entire inventoryarea were detected. Search swath widths were adjusted asneeded according to variations in terrain, walking speed,associated vegetation, and target species. In heavy cover and/or for difficult-to-see species, swath widths were as narrowas 25 yards. In very open terrain and/or for highly visiblespecies such as salt cedar (Tamarix ramosissima), some effectiveEDSWs were 100 yards or greater. Inventorying steepterrain using the EDSW method was not always possible,so in that case crew members used binoculars to visuallyscan the open but inaccessible hillsides for suspected targetspecies. Binoculars were also used to search flats and washbottoms for target species in any openings surrounded byimpenetrable woody vegetation.Each inventoried area was assigned a detection confidencevalue based on the crew’s estimated ability to see 0.01-acreand larger infestations of the least visible target species,taking into account terrain, vegetation cover, and the sizeand growth stage of the targeted plant species. Detectionconfidence was broken into three categories: low (1 to 50%),medium (51 to 89%), and high (90 to 100%).Locations of all target species were documented usingGPS units with 2 to 5 m accuracy (Figure 3). Crews alsorecorded the location and documented the identity of anyother nontarget species they encountered if that NIS had aknown history of invasiveness in other regions in the West.The crew recorded the occurrence of target species on a hardcopy map (U.S. Geological Survey 7.5-minute topographicalmaps) in any situation where GPS satellite reception was notpossible (such as in narrow side canyons) or in cases of GPSequipment malfunction.28Inventory and Survey Methods for Nonindigenous Plant Species