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Submitted to: Geocarto International
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/12/2013 Publication Date: 5/1/2014 Citation: Fletcher, R.S. 2014. Applying broadband spectra to assess biological control of saltcedar in West Texas. Geocarto International. 29(4):383-399. 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. In Texas, natural resource managers, government officials, and scientists need effective means for monitoring biological control of saltcedar with the saltcedar leaf beetle. A ground-based study was conducted in West Texas to compare the canopy reflectance characteristics of saltcedar trees exhibiting feeding damage caused by the saltcedar leaf beetle to other cover types. Wavelengths sensitive to changes in leaf pigment concentrations (red wavelength, 630-690 nanometer range) and to reduction in foliage content (near-infrared wavelengths, 770-895, 860-1040 nanometer range) were useful for discriminating severe feeding damage and total defoliation to saltcedar trees, respectively, from other cover types. Wavelengths identified in this study correspond to wavelengths used in commercial airborne and satellite-borne multispectral imaging systems, thus supporting future exploitations of those systems to monitor biological control of saltcedar within complex landscapes. Technical Abstract: In Texas, natural resource managers, government officials, and scientists need effective means for monitoring biological control of saltcedar (Tamarix spp.) with the saltcedar leaf beetle (Diorhadba spp.). This study was conducted to evaluate broadband spectra within visible, red-edge, and near-infrared wavelengths to discriminate saltcedar trees exhibiting feeding damage caused by the saltcedar leaf beetle from other land cover types. Field spectra were collected at two study sites near Presidio, Texas, in 2010 and 2011. Spectral bands evaluated were coastal blue (400-450 nm), blue (450-510 nm), green (510-580 nm), yellow (585-625 nm), red (630-690 nm), red-edge (705-745 nm), and near-infrared (770-895, 860-1040 nm). Data were evaluated with analysis of variance (alpha = 0.05) and Scheffe's multiple comparison test (alpha = 0.05). The red band generally separated stressed saltcedar trees exhibiting changes in their canopy color from other land cover features. Near-infrared bands separated defoliated saltcedar trees. Broadband spectra has potential as a tool for distinguishing saltcedar trees exhibiting feeding damage caused by the saltcedar leaf beetle from other associated features, thus supporting future exploitations of airborne and satellite-borne multispectral systems to monitor biological control of saltcedar within complex landscapes. |
