A model with four layered media is developed for the calculation of the radio loss in forests. In this model two lossy dielectric layers placed over a conducting flat earth are used to represent the crown and the trunk of the trees. Dyadic Green's functions in their eigenfunction expansion forms are used to analyze this model, and the electromagnetic fields are obtained from these functions. The theoretical results of the radio loss for vertical and horizontal radiating dipoles and for typical forests agree with the available experimental data. For this comparison the parameters for the layer representing the crown of the trees were estimated.