Separating crested wheatgrass using field hyperspectral data in the native prairie of southwestern Saskatchewan

Crested wheatgrass (Agropyron cristatum) is an introduced invasive grass species in North American grasslands. It was initially seeded to increase the grazing duration but is now threatening native grassland biodiversity. In this study we investigated which biophysical and spectral properties (hyperspectral and simulated multispectral) distinguish crested wheatgrass from native grasses. We further assessed whether spectral indices, linked to biophysical traits, could distinguish crested wheatgrass from native grasses. We collected field data of hyperspectral reflectance, leaf area index (LAI), biomass, and vegetation cover. Crested wheatgrass sites have higher grass cover, height, LAI, and biomass (total, live, and dead), but lower bare ground than native grasses. Hyperspectral data showed lower visible and SWIR reflectance for crested wheatgrass than for native grasses. SWIR spectral indices for hyperspectral data, SWIR and visible spectral indices for simulated Sentinel-2A data and visible spectral indices for PlanetScope SuperDove data discriminated crested wheatgrass from native grasses. These findings will advance invasive grass monitoring by shifting the focus from phenology to biophysical properties-based detection, supporting management of crested wheatgrass and restoration of native grassland ecosystems.