Fractional Vegetation Cover Derived from UAV and Sentinel-2 Imagery as a Proxy for In Situ FAPAR in a Dense Mixed-Coniferous Forest?

The fraction of absorbed photosynthetic active radiation (FAPAR) is an essential climate variable for assessing the productivity ecosystems. Satellite remote sensing provides spatially distributed FAPAR products, but their accurate and efficient validation challenging in forest environments. As linked to canopy structure, it may be approximated by fractional vegetation cover (FCOVER) under assumption that incoming either or passed through gaps canopy. With FCOVER being easier retrieve, activities could benefit from a priori information on FCOVER. Spatially available satellite can retrieved imagery Unmanned Aerial Vehicles (UAVs) at centimetric resolution. We investigated sensing-derived as proxy situ dense mixed-coniferous forest, considering both absolute values spatiotemporal variability. Therefore, direct measurements, acquired with Wireless Sensor Network, were related derived UAV Sentinel-2 (S2) different seasons. results indicated aggregated UAV-derived was close (RMSE = 0.02) during peak period when almost closed. S2 product underestimated > 0.3), which we attributed generic nature retrieval algorithm coarser resolution product. concluded used measurements canopies. another key finding, spatial variability consistently surpassed FAPAR, also well-reflected products. recommend integrating this experimental finding consistency criteria context ECV quality assessments. To facilitate sampling activities, further suggest benchmark sizes measurements. Finally, our study contributes refining protocols needed improvement estimates