Detection and Classification of Plant Species through Spectir Airborne Hyperspectral Imagery in Clark County, Nevada

The non-native Saltcedar (Tamarix ramosissima Ledeb.) and the native Honey mesquite (Prosopis Glandulosa Torr.), exist in abundance in Clark County, NV. We are using remote sensing to measure changes in distribution and abundance of these species. We collected six strips of 1m-resolution SpecTIR hyperspectral images in Clark County on May, 2005. SpecTIR has 227 spectral bands ranging from 0.45 to 2.45 μm. We have explored the properties of these high-spatial resolution hyperspectral images, and we are now testing the potential for detecting and classifying Tamarix, Prosopis and other plant species along Muddy River. Spectral band selection and feature extraction methods are being used to reduce the dimension of the hyperspectral data and the distinguishable spectral characteristics are chosen for SAM (Spectral Angle Mapper) and supervised maximum likelihood (ML) classifiers. Terrestrial information and habitat knowledge of the vegetation are also incorporated into the classifier. The accuracy of classification results are being verified in relation to ground surveys. Preliminary results will be reported on this project. The results will provide evidence for a proposed project of vegetation delineation and change detection in Clark County. BACKGROUND AND INTRODUCTION Remote sensing technique is an important approach to monitor the large-scale ecosystem health. Without possible sampling bias derived from field work, remote sensing can be used to detect and measure crucial changes to habitat. Particularly, remote sensing is useful to identify the indicators for the frail ecosystem. By monitoring indicators, land owners can asses and adjust the current management strategies. Vegetation spectral signatures often share the similar patterns. This causes the difficulty in separating the different vegetation species using conventional multispectral imagery. Recently hyperspectral remote sensing techniques have been broadly applied for detecting and distinguishing the vegetations. Due to its exceptionally high spectral resolution, hyperspectral imaging offers great potential in mapping the abundance of particular species over large spatial extents. For example, several recent publications have applied hyperspectral image analysis to mapping individual invasive species with varying levels of success (Ustin, Scheer et al. 2001; Lass, Thill et al. 2002; Williams and Hunt 2002; Underwood, Ustin et al. 2003). The non-native Saltcedar (Tamarix ramosissima Ledeb.) and other the native vegetation, such as Honey mesquite (Prosopis Glandulosa Torr.), exist in abundance in Clark County, NV. Saltcedar was first introduced in the U.S. from southeastern Europe and Asia to reclaim eroded areas and prevent further loss of stream banks, primarily in the southwest. However, saltcedar has lower value to wildlife habitat and consumes tremendous amount of water, which contribute spring drought. Furthermore, its leaves are concentrated with salts. Once releasing these salts, the surface soil can become highly saline, thus preventing possible colonization by many native plant species. In Clark County, Saltcedar invades riparian habitats and displaces native flora and fauna to a large extent. It is a primary concern of the local government to evaluate the disturbance caused by saltcedar to the arid ecosystem. By applying hyperspectral remote sensing technique, it is our hypothesis that we can survey and monitor the distribution of saltcedar along the riparian corridor and abundance of other plant species in Clark County.