Effects of alternative management regimes on forest stand structure, species composition, and income: a model for the Italian Dolomites

Abstract

The aim of this study was to predict the long-term effects of alternative management regimes for uneven-aged mixed-species forests in the Italian Dolomites, among the most beautiful in the Alps range. For this purpose, a non-linear matrix model of stand growth was estimated from re-measured stands, and the predictions compared with actual data. Then, long-term simulations were used to determine the effects of (i) extracting some mortality only; (ii) applying Susmel's (1980) management guides; (iii) cutting only trees above a diameter limit, (iv) saving the beech, and (v) continuing the current harvest rate. The ecological criteria to evaluate the different management regimes were basal area and stand composition by tree species and size. The economic criterion was the net present value of the harvests. The results suggest that, for a 10-year cutting cycle, applying Susmel's guide or a diameter-limit cut of 70 cm for conifers and 50 for beech would keep diversity of species and size equal to that of an unmanaged stand, though lowering basal area. Of the two, Susmel's guide would give 25% higher income. However, income could be doubled by lowering the diameter-limit cut to 60 cm for conifers and 45 for beech. This would give the same basal area and species diversity, but decrease size diversity by about 6%. The policy that did not allow to cut beech resulted in stands that had less beech than those obtained by Susmel's guide or diameter-limit cuts. Perpetuating the current cutting rate gave the highest tree size diversity, but lower species diversity and the lowest income. Of cutting cycles of 5, 10, and 15 years, the longest gave, other things being equal, the highest basal area and size diversity, slightly lower species diversity, but substantially lower income.