Joint Analysis of Optical and SAR Vegetation Indices for Vineyard Monitoring: Assessing Biomass Dynamics and Phenological Stages Over Po Valley, Italy

Abstract

Multi-polarized Synthetic Aperture Radar (SAR) technology has gained increasing attention in agricultural applications. It offers unique capabilities for monitoring vegetation dynamics thanks to its all-weather, day-and-night operation and high revisit frequency. This study presents, for the first time, a comprehensive analysis combining dual-polarimetric radar vegetation index (DpRVI) with optical indices to characterize vineyard crops. Vineyards exhibit distinct non-isotropic scattering behavior due to their pronounced row orientation, making them particularly challenging and interesting targets for remote sensing. The study further explores the relationship between DpRVI and optical vegetation indices, revealing the complementary nature of their information. The low correlation between DpRVI and optical indices ( $r \leq 0.24$ ) suggests they capture distinct vegetation structure and health aspects. Notably, DpRVI exhibits a parabolic trend across the growing season, which may reflect biomass dynamics as inferred from the Winkler Index. Unlike optical indices reflecting vegetation greenness, DpRVI appears more directly related to biomass growth, aligning with specific phenological phases. This research aligns with the objectives of the PNRR-NODES project, which promotes nature-based solutions (NbS) for sustainable vineyard management. The application of DpRVI for monitoring vineyards is part of integrating remote sensing techniques into the broader field of strategies for climate-related change adaptation and risk reduction, emphasizing the role of innovative SAR-based monitoring in sustainable agriculture.