The microwave interacting vegetation surfaces are composed of layered media and is made up of the layers of consecutive leaves, branches, roots and stems of varying dielectric constants situated at a certain level above the surface of earth (Woodhouse 2006a, b; Santoro et al. 2005; Moghaddam 2009). The microwave interacting woody vegetation with variable dielectric constants (due to compositional change) may lead to a change in the direction of reflected microwaves at least to some extent. The microwaves following the interference with woody vegetation, the reflected signal properties such as the wavelength, incidence angle, polarization and terrain surfaces are greatly influenced by the surface roughness, local incidence angle, dielectric constant and surface morphology, respectively (Raney 1998; Leckie

1998) . In order to address the reflection properties of a relatively smooth surface from any part of the vegetation, the Fresnel reflectivity can be employed. For under­standing, the schematic representation of the Fresnel reflection in two different media of varying dielectric constants for air and homogeneous soil which corre­sponds to the refractive indices, n and n2 (respectively) is shown in Fig. 12.1 (Hajnsek and Papathanassiou 2005). Based on this, the following Eqs. 12.13 and 12.14
can be used to calculate the Fresnel reflection constants for horizontal and vertical polarization, respectively.

Where e corresponds to the dielectric constant and м is the unit applied to a natural material of non-ferromagnetic behaviour (natural soil).