Discriminating saltcedar (Tamarix ramosissima) from sparsely distributed cottonwood (Populus euphratica) using a summer season satellite image

Accurate mapping of saltcedar (Tamarix ramosissima) and cottonwood (Populus euphratica) using remote sensing images is required to study the dynamic relationship between these two species. Our study used pixel-based and semi-object-based methods to classify a high spatial resolution QuickBird image acquired during the summer in northern China, where both saltcedar and cottonwood are native species. The pixel-based classification results revealed that spectral bands alone were not sufficient to discriminate saltcedar from cottonwood trees due to their similar foliage reflectance in the summer. Including texture measures did not improve the result. The unique crown shapes and shadows associated with sparsely distributed cottonwood were used to facilitate the semi object-based method. The overall accuracy of the object-based classification result increased 15 percent compared to that of the pixel-based classification results and showed significant improvement in the discrimination between saltcedar and cottonwood.