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Remote sensing derived maps of tamarisk (2009) and beetle impacts (2013) along 412 km of the Colorado River in the Grand Canyon, Arizona

April 10, 2018

These data were compiled for quantifying the area of tamarisks (Tamarix spp.) in May 2009 and to quantify the area of beetle-impacted tamarisk in May 2013 within the 2009 tamarisk classification from Glen Canyon Dam to Separation Canyon, a total distance of 412 km along the Colorado River using the 2009 and 2013 0.2 m high-resolution airborne imagery datasets. We classified tamarisk presence in 2009 using the Mahalanobis Distance method with a total of 2,500 training samples, and assessed the classification accuracy with an independent set of 7,858 samples across 49 image quads. A total of 214 ha of tamarisk was detected in 2009 along the Colorado River, where each image quad, on average, included 8.4 km section of the river. Tamarisk detection accuracies varied across the 49 image quads, but the combined overall accuracy across the entire study region was 74%. The 2013 Beetle-impacted dataset was created by calculating NDVI values using 2009 and 2013 multispectral imagery only within pixels classified as tamarisks in the 2009 multispectral dataset. A region-specific NDVI ratio of >1.5 decline between the two image dates (2009NDVI/2013NDVI) was developed to identify tamarisks impacted by beetle herbivory. The area of beetle-impacted tamarisks varies greatly throughout the canyon, but totaled 32.1 hectares. The Glen Canyon area indicated the greatest amount of hectares of beetle-impacted tamarisk in the study region. These data are intended to be useful for monitoring, research and management related to riparian vegetation. These data can be used for GIS activities including; examining the densities of tamarisk spatially, and change detection analysis. These datasets was designed specifically to assist in quantifying the area of tamarisk impacted by the tamarisk beetle, a biological control agent that arrived in the state of Arizona in 2009. Researchers and managers can use this data to identify beetle-impacted tamarisk areas for further study to better understand the response of the plant communities to tamarisk defoliation and possible mortality. This data may also aid in planning possible restoration efforts by identifying heavily beetle-impacted areas.

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These data are associated with the journal manuscript: Muehlbauer, J. D., Kennedy, T.A., Copp, A.J., and Sabol, T.A., 2016, Deleterious effects of net clogging on the quantification of stream drift, Can. J. Fish. Aquat. Sci.,