THE MAXIMUM DENSITY CONCEPT APPLIED TO UNEVEN-AGED MIXED-SPECIES STANDS

In even-aged pure stands, the relationship between density and quadrat ic mean diameter of different stands can be described by a hyperbola, the coefficients of which depend allometrically on dominant height (St erba's modified Competition Density Rule). From the equations describi ng these relationships the slope of Reineke's maximum density line can be calculated and (for a given data set) tested against the hypothesi s that this slope is -1.605. Data from 134 even- and uneven-aged mixed species stands in northern Idaho and northwestern Montana showed that this slope depended on the skewness of the dbh1.5 distribution, which in turn was correlated with structural stand characteristics like ''u nevenagedness'' and species mixture. The parameters of the extended Co mpetition Density Rule were simultaneously estimated by nonlinear regr ession under an assumption relating asymptotic dominant height and max imum basal area by habitat type. Results demonstrated that both the ma ximum basal area at a given dominant height are higher in even-aged pu re stands (with smaller skewness of the dbh1.5 distribution) than in u nevenaged mixed stands. Furthermore, the differences in maximum stem n umber and maximum basal area resulting from differing skewness decreas e with increasing dominant height. Large differences in maximum basal area can be shown between different habitat types and any given site i ndex, thus demonstrating that habitat types can be used to distinguish yield levels sensu Assmann.