Estimation of leafy spurge cover from hyperspectral imagery using mixture tuned matched filtering

Leafy spurge, Euphorbia esula L. is an adventive, perennial weed that infests approximately 1.2 million ha of land in North America. It often forms dense stands that displace native vegetation and useful forage plants on rangelands and in riparian habitats. Leafy spurge is a good candidate for detection via remote sensing because the distinctive yellow-green color of its bracts is spectrally unique when compared to co-occurring green vegetation. During 1999, Airborne Visible Infrared Imaging Spectrometer (AVIRIS) imagery was acquired in northeastern Wyoming and ground cover data were collected. Mixture tuned matched filtering (MTMF), a specialized type of spectral mixture analysis, was used to estimate leafy spurge canopy cover and map leafy spurge distribution. Overall performance of MTMF for estimating percent cover of leafy spurge for all sites was good (r2=0.69) with better performance in prairie areas (r2=0.79) and poorer performance occurring on wooded sites (r2=0.57). However, results demonstrated that in open canopies with leafy spurge in the understory, the spectral signature is sufficiently distinct to be detectable. The techniques presented here could be used for constructing leafy spurge distribution and abundance maps with satellite hyperspectral data for larger regional areas.