This paper deals with the numerical simulation (using a LES approach) of the interaction between an atmospheric boundary layer (ABL) and a canopy, representing a forest cover. This problem was studied for a homogeneous configuration representing the situation encountered above a continuous forest cover, and a heterogeneous configuration representing the situation similar to an edge or a clearing in a forest. The numerical results, reproduced correctly all the main characteristics of this flow, as reported in the literature: the formation of a first generation of coherent structures aligned transversally from the wind flow direction, the reorganisation and the deformation of these vortex tubes to horse shoe structures. The results obtained, introducing a discontinuity in the canopy (reproducing a clearing or a fuel break in a forest), were compared with experimental data collected in a wind tunnel. The results confirmed the existence of a strong turbulence activity inside the canopy at a distance equal to 8 times the height of the canopy, referenced in the literature as an Enhance Gust Zone (EGZ) characterized by a local peak of the skewness factor.