In order to study the interactions between the important processes within a wildland fire, Los Alamos National Laboratory and the USDA Forest Service are continuing to develop the HIGRAD/FIRETEC wildfire behavior model. HIGRAD/FIRETEC is a coupled atmosphere/wildfire behavior model and is based on conservation of mass, momentum, species, and energy. HIGRAD/FIRETEC is a three-dimensional transport model that uses a compressible-gas formulation to couple its physics based wildfire model with the motions of the local atmosphere. This model has been used to examine fire behavior and the interaction between the fire and atmosphere in a number of idealized simulations, including idealized grass fires and homogenized understory and canopy simulations. These idealized simulations illustrate the importance of the interaction between fire, atmosphere, and vegetation structure. We are beginning to use HIGRAD/FIRETEC to simulate fires in fuel beds with more realistic representations of vegetation. Among these fuel beds are ponderosa pine forests using individual tree data from experimental sites near Flagstaff and pinion-juniper stands using data from areas near Los Alamos. These simulations are giving us a chance to examine the interaction of wind in discontinuous fuel beds and more specifically, investigate the role that the canopy structure might serve in fires of these types. By comparing the idealized and homogenized fuel bed simulations with the more realistic and inhomogeneous fuel beds we hope to learn more about the sensitivity of fire behavior to stand structure under various wind conditions.