We adjusted the expression between the crown-projected area and the diameter of the trees without competition as a continuation of the study of functional density relationships of mixed Nothofagus stands. This expression allowed us to define the starting competition line for these stands. Both the lower line and the maximum density line (defined in a previous article) were used to develop the density management diagram for pure and mixed Nothofagus stands. This diagram may be used for silvicultural planning purposes. The index, called the "Crown Competition Factor", was adjusted as a practical application and may be used to characterize the competitive status of a stand and to develop growth models.