TY - JOUR
T1 - Remote sensing of tamarisk beetle (Diorhabda carinulata) impacts along 412 km of the Colorado River in the Grand Canyon, Arizona, USA
AU - Bedford, Ashton
AU - Sankey, Temuulen T.
AU - Sankey, Joel B.
AU - Durning, Laura
AU - Ralston, Barbara E.
N1 - Funding Information:
This research was funded by the U.S. Bureau of Reclamation through the Glen Canyon Dam Adaptive Management Program. The authors acknowledge the National Park Service, Grand Canyon National Park, and Glen Canyon National Recreation Area for providing permission to conduct the field research. We thank Dr. Erik Schiefer who advised Ashton Bedford at Northern Arizona University during his M.S. thesis ( whose guidance was instrumental in developing the code to calculate the classification accuracy assessments for the study area quads. We also thank Emily Palmquist from the USGS Grand Canyon Monitoring and Research Center for providing vegetation ground survey data. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. The data from this study are published as a U.S. Geological Survey data release ( Bedford, 2016 ) in which a portion of this work was developed. We thank Peg Shippert of Harris Geospatial, Bedford et al., 2018 ) that is available for download at: https://doi.org/10.5066/F72B8X71 .
Publisher Copyright:
© 2018
PY - 2018/6
Y1 - 2018/6
N2 - Tamarisk (Tamarix spp.) is an invasive plant species that is rapidly expanding along arid and semi-arid rivers in the western United States. A biocontrol agent, tamarisk beetle (Diorhabda carinulata), was released in 2001 in California, Colorado, Utah, and Texas. In 2009, the tamarisk beetle was found further south than anticipated in the Colorado River ecosystem within the Grand Canyon National Park and Glen Canyon National Recreation Area. Our objectives were to classify tamarisk stands along 412 km of the Colorado River from the Glen Canyon Dam through the Grand Canyon National Park using 2009 aerial, high spatial resolution multispectral imagery, and then quantify tamarisk beetle impacts by comparing the pre-beetle images from 2009 with 2013 post-beetle images. We classified tamarisk presence in 2009 using the Mahalanobis Distance method with a total of 2500 training samples, and assessed the classification accuracy with an independent set of 7858 samples across 49 image quads. A total of 214 ha of tamarisk were detected in 2009 along the Colorado River, where each image quad, on average, included an 8.4 km segment of the river. Tamarisk detection accuracies varied across the 49 image quads, but the combined overall accuracy across the entire study region was 74%. Using the Normalized Difference Vegetation Index (NDVI) from 2009 and 2013 with a region-specific ratio of >1.5 decline between the two image dates (2009NDVI/2013NDVI), we detected tamarisk defoliation due to beetle herbivory. The total beetle-impacted tamarisk area was 32 ha across the study region, where tamarisk defoliation ranged 1–86% at the local levels. Our tamarisk classification can aid long-term efforts to monitor the spread and impact of the beetle along the river and the eventual mortality of tamarisk due to beetle impacts. Identifying areas of tamarisk defoliation is a useful ecological indicator for managers to plan restoration and tamarisk removal efforts.
AB - Tamarisk (Tamarix spp.) is an invasive plant species that is rapidly expanding along arid and semi-arid rivers in the western United States. A biocontrol agent, tamarisk beetle (Diorhabda carinulata), was released in 2001 in California, Colorado, Utah, and Texas. In 2009, the tamarisk beetle was found further south than anticipated in the Colorado River ecosystem within the Grand Canyon National Park and Glen Canyon National Recreation Area. Our objectives were to classify tamarisk stands along 412 km of the Colorado River from the Glen Canyon Dam through the Grand Canyon National Park using 2009 aerial, high spatial resolution multispectral imagery, and then quantify tamarisk beetle impacts by comparing the pre-beetle images from 2009 with 2013 post-beetle images. We classified tamarisk presence in 2009 using the Mahalanobis Distance method with a total of 2500 training samples, and assessed the classification accuracy with an independent set of 7858 samples across 49 image quads. A total of 214 ha of tamarisk were detected in 2009 along the Colorado River, where each image quad, on average, included an 8.4 km segment of the river. Tamarisk detection accuracies varied across the 49 image quads, but the combined overall accuracy across the entire study region was 74%. Using the Normalized Difference Vegetation Index (NDVI) from 2009 and 2013 with a region-specific ratio of >1.5 decline between the two image dates (2009NDVI/2013NDVI), we detected tamarisk defoliation due to beetle herbivory. The total beetle-impacted tamarisk area was 32 ha across the study region, where tamarisk defoliation ranged 1–86% at the local levels. Our tamarisk classification can aid long-term efforts to monitor the spread and impact of the beetle along the river and the eventual mortality of tamarisk due to beetle impacts. Identifying areas of tamarisk defoliation is a useful ecological indicator for managers to plan restoration and tamarisk removal efforts.
KW - Dam
KW - Herbivory
KW - High resolution image
KW - Invasive
KW - Riparian
KW - River regulation
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U2 - 10.1016/j.ecolind.2018.02.026
DO - 10.1016/j.ecolind.2018.02.026
M3 - Article
AN - SCOPUS:85042276420
SN - 1470-160X
VL - 89
SP - 365
EP - 375
JO - Ecological Indicators
JF - Ecological Indicators
ER -