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Submitted to: Geocarto International
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 1/16/2013 Publication Date: 4/1/2014 Citation: Fletcher, R.S. 2014. Employing spatial information technologies to monitor biological control of saltcedar in West Texas. Geocarto International. 29(3):332-347. Interpretive Summary: Saltcedar is an weedy shrub that was originally established for stream channel stabilization and windbreaks in the middle 1800s. Since that time, it has become a prolific invasive weed species that is difficult to control in riparian systems. The saltcedar leaf beetle has shown promise as a biocontrol agent for saltcedar invasions in the United States. In Texas, natural resource managers need assistance in monitoring biological control of invasive saltcedars. A conventional color digital imaging camera was integrated with a global positioning system receiver to monitor biological control of saltcedar in west Texas. On the aerial imagery obtained with the camera, saltcedar plants exhibiting severe feeding damage, and total defoliation caused by beetle and larvae feeding appeared in orange to orange brown color tones and gray color tones, respectively, leading to their identification from other cover types. By linking the camera system with a global position system receiver, the location of each image was recorded, allowing the viewer to develop point distribution maps within a geographic information system showing areas with damaged saltcedar trees along a 155.8-km transect for two dates. Saltcedar plants stress symptoms are the same when it comes to beetle feeding; thus, this technique is applicable to other areas. Technical Abstract: The saltcedar leaf beetle (Diorhadha spp.) has shown promise as a biocontrol agent for saltcedar (Tamarix spp.) invasions in the United States. In Texas, natural resource managers need assistance in monitoring biological control of invasive saltcedars. This study describes application of a medium format conventional color digital camera and global positioning system (GPS) and geographic information system (GIS) technologies to check biological control of saltcedar in West Texas. On July 8 and September 8, 2011, conventional color airborne digital imagery was collected along a 155.8-km transect covering portions of Presidio and Brewster counties of Texas. The camera was tethered to a GPS receiver that geotagged each image and saved the coordinates to a key-hole marked up language file that was viewable on Google Earth. Saltcedar trees exhibiting severe feeding damage and those that were totally defoliated were easily identified on the imagery. The former appeared in orange to brown color tones; the latter exhibited gray color tones. Point distribution maps showing locations of saltcedar trees exhibiting feeding damage were developed from GPS information in the GIS. Coordinate points on the map were linked to the corresponding image, permitting the user to have quick access to view imagery. The results of this study show a practical method for monitoring biological control of saltcedar. |
