Introduction:

Density management diagrams (DMDs) are useful tools for characterizing and managing stand density.

Objective:

To develop a DMD to schedule thinnings in the natural mixed-species forests of the El Salto region, Durango.

Materials and methods:

The data were collected in 441 temporary sampling plots in 263 mixed-species stands with mainly species of the Pinus and Quercus genus. The DMD was based on the Hart-Becking index and a relationship of two allometric equations: 1) the quadratic mean diameter (dg, cm) with the density (N, trees·ha−1) and dominant height (Hd, m), and 2) the volume (V, m3·ha−1) with the dg, Hd and N. In fitting equations, the ordinary Nonlinear Least Squares (NLS) method was used simultaneously. The maximum density limit was estimated by potential quantile regression that related N to Hd.

Results and discussion:

Efficient goodness-of-fit statistics were reported in the fitted models, in terms of Root Mean Square Error (2.29) and coefficient of determination (0.86). The DMD suggests applying thinnings below the maximum density line to avoid mortality. Through the DMD it is possible to evaluate different silvicultural alternatives, schedule thinnings, maximize growth space, promote tree growth and improve forest products.

Conclusion:

The DMD developed is useful for thinning scheduling to obtain saw-timber at rotation age.

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