Development of a stand density management diagram for even-aged pedunculate oak stands and its use in designing thinning schedules

Density management is the usual method used by silviculturists to achieve a desired future stand condition, and one of the most effective methods of design, display and evaluation of alternative density management regimes in even-aged stands is the use of stand density management diagrams. In the present study, we describe a method for developing thinning schedules for even-aged pedunculate oak (Quercus robur L.) stands in Galicia (north-western Spain), using a density management diagram. The diagram integrates the relationships among stand density, dominant height, quadratic mean diameter and stand volume in a single graph. The data used in its construction were obtained from 172 sample plots located throughout Galicia. The diagram is basically composed of two equations: the first relates the quadratic mean diameter to the stand density and dominant height; the second relates the stand volume to the quadratic mean diameter, stand density and dominant height. These equations were fitted simultaneously using full information maximum likelihood. The relative spacing index is used to characterize the growing stock and the diagram provides isolines for dominant height, number of trees per hectare, quadratic mean diameter and stand volume. Dominant height isolines together with the site index curves allow specification of the timing of thinnings while intermediate and final harvest volumes are calculated using the stand volumes isolines.