Vegetation effects on electromagnetic wave propagation can have a strong impact on many localization or communication systems. This situation explains an increasing interest in the development of tree attenuation and scattering models which could help in the characterization of complex propagation environments. In this paper, we propose a general methodology to compute propagation effects due to a set of trees based on a point scattering model and the multiple scattering theory. We show its capacity to generate realistic simulations in good accordance with S band measurements.