Stem analysis-based procedure to estimate a posteriori whether the long-term timber yield of a forest has been sustained

Introduction: Sustained timber yield is the ability of the forest to maintain its production at a similar level through time.Objective: To propose a procedure to estimate a posteriori whether the long-term timber yield of a forest has been sustained by assessing the heights and diameters reached by same-aged trees but established in different years.Materials and methods: Diameters were gotten from stem analysis and heights were estimated by linear interpolation. Trees were grouped by size, and heights and diameters of same-aged trees established in different years were regressed versus the Year at which Trees Reached that Age (YTRA). All the trees were analyzed by multiple regression, regardless of the size groups; the regression model included the reciprocal of the tree age and the YTRA as explanatory variables for height and diameter.Results: Regression of heights and diameters versus YTRA at different ages (10, 20,..., 70) showed positive slopes, indicating that the more recently established trees had better growth and no evidence of deterioration of timber yield over time was found. The results on all the trees as a whole agreed with results for trees by size groups; these results coincided with what forest managers observed in situ.Conclusion: The procedure provides user-friendly tools to detect any negative changes that may jeopardize timber yield sustainability, identify possible causes, and implement corrective management practices.