The reflectance signal from the forest tree canopy is influenced by the optical properties of the background formed by understory vegetation. Our study shows that the herb-moss layer in the forest tends to be brighter in the visible wavelength when the canopy above is more closed because of the specific properties of plants grown in low light. When leaf-area-based chlorophyll content falls below approximately 150 mg·m–2, reflectance in the red region of the spectrum increases compared with that of the background. The best descriptors of the herb-moss layer for deriving optical parameters are herb layer dry mass for the visible wavelength range and total aboveground water mass for near-infrared (NIR) reflectance. In addition, chlorophyll content per leaf area considerably improves the red reflectance estimate. © 2009 Canadian Aeronautics and Space Institute.