Spectral scattering properties of Scots pine shoots

Studies the relationship between optical and geometrical properties of Scots pine (Pinus sylvestris) shoots. For the purpose, measurements of shoot bidirectional reflectance (BDR), bidirectional reflectance distribution function (BRDF) as well as shoot spectral reflectance at different incident and view angles were carried out under laboratory conditions. In addition, different geometrical parameters of needles and shoots were measured. The results indicated that scattering from the Pinus sylvestris shoots, modeled as a cylinder, drastically differs from Lambertian surface: the essential part of the incident light beam is transferred forward due to transparency, but the scattered radiation is usually concentrated around the backscattering direction. In directions perpendicular to incident beam direction (scattering angles 90° and 270°) scattering is small, especially in the blue and red spectral regions. The shape of the BRDF as function of scattering angle is maximally smooted in the near infrared (NIR) spectral region and most variable in the blue region. One of the important factors that determines the shape of the BRDF seems to be the specular reflection, intensity of which is determined by Fresnel´s law