Maximum density and density management diagram for mixed-species forests in Durango, Mexico

Abstract Introduction: Stand density affects productivity and the structure and functions of forests. Objectives: To compare maximum density lines for mixed-species forests adjusted with ordinary least Squares (OLS) and Stochastic Frontier Regression (SFR); and generate a density management diagram (DMD) to prescribe thinning. Materials and methods: The data was obtained in mixed-species stands from the Forest Management Unit 1005 "Santiago Papasquiaro y Anexos" in Durango, Mexico. The density-size relationship was established using the Reineke’s model. The maximum density line was adjusted with OLS and SFR, the latter with the half-normal (H-N), normal-exponential (N-E) and normal-truncated (N-T) approaches. The DMD was constructed with the SFR equation with the normal-truncated distribution approach. Results and discussion: The maximum density line, modeled through SFR with N-T approach showed better fit to the upper limit of the maximum density of the mixed-species stand data. DMD suggests that thinning for these stands can be applied with high cutting intensities, contrary to conventional practices, where rarely more than 30 % of the basal area or volume is cut. Conclusion: The maximum density line for mixed-species forests in Durango, Mexico, was generated with stochastic frontier regression, as a normal-truncated model.