Compact polarimetric response of native grassland and seeded forage across a gradient of Southern Alberta Prairie ecoregions

Canada’s remaining intact native Prairie grasslands are highly fragmented and difficult to distinguish from seeded forage using conventional satellite methods due to their phenological similarity. This study evaluated the potential of compact polarimetric (CP) C-band synthetic aperture radar (SAR) from the RADARSAT Constellation Mission (RCM) (3 m resolution) to discriminate between native grassland and seeded forage land cover types across five Southern Alberta sites representing diverse plant communities, soils and management regimes. Random forest classification with recursive feature elimination was applied to multitemporal CP-SAR features, including polarimetric decompositions and Stokes parameters. Results demonstrated that C-band CP-SAR effectively captures structural differences between native and seeded sites, with classification accuracies exceeding 92% in Dry and Moist Mixedgrass sites, with slightly lower accuracy (90–91.5%) in Foothills Fescue and Aspen Parkland sites. Early (May) and late-season (August–September) acquisitions, as well as imagery following large regional rainfall events, were particularly important for separability. Stokes parameters and degree of polarization consistently ranked highest among most informative features. The findings highlight the value of high-resolution CP-SAR for regional-scale mapping of rangelands, particularly where optical sensors are limited by cloud cover, providing new opportunities for operational monitoring of Canada’s native grasslands.