Air flow in the natural environment affects the distribution of organisms, mechnical stresses, heat losses by convection, and moisture distribution. Air flow was visualized by bubble tracers in a wind tunnel, and the flow patterns over solid barriers 5 and 15 cm high and 0%, 25%, and 47% porosity barriers, each 10 cm high, were photographed. The leeward circulation pattern is very similar regardless of the barrier height. The leeward effect of the barrier extends a greater distance for the 47% porosity than for the 25% and 0% porosities. The three-dimensional characteristics of visualized turbulent flow clearly indicate the limitations of cup anemometers for measuring field velocities since these instruments do not respond to angles of attack from 70s to 90s. © Ecological Society of America. Abstract reproduced by permission.