Abstract: The close spaced Populus deltoides cv. ‘Lux' I-69/55 plantations have sharper-angled branches and low percentage of skeleton branches. The optimum stand density appears when the leaf area index, reaches 7.81 and the leaf area density amounts to 0.8~0.9. The light distribution within the canopy is subject to the leaf area index and the extinction coefficient. The light intensity weakens faster in closed plantations. Taking 8 % of the relative light intensity as a criticle light intensity, the close spaced plantation possessed the lowest productivity and the medium density plantation the highest at the sixth year. The widely spaced plantation's productivity approached that of the medium density plantation at the seventh year.