Optimizing thinnings and rotation of Scots pine and Norway spruce mixtures

• Main Authors: Vettenranta, Jouni, Miina, Jari
• Format: Article
• Language: English
• Published: Finnish Society of Forest Science 1999-01-01
• Series: Silva Fennica
• Online Access: https://www.silvafennica.fi/article/671

The study describes a simulation-optimization system which uses spatial models for diameter and height growth, crown ratio and tree mortality for Scots pine and Norway spruce mixtures. The optimal one- and two-thinning regimes of six initial stands with varing species composition were solved by using nonlinear optimization. The soil expectation value (SEV) at 3% interest rate was used as a management objective. The regimes are determined by taking into account the stand basal areas before the thinnings, the removal percentages for small, medium-sized and large pines and spruces, and the stand basal area before the final felling. The greatest SEV (8900 FIM haâ1) was attained with the initial stand where the proportion of pines was 65% of the number of the stems. In the two-thinning regime, the first thinning was conducted at the age of 39 years when the stand basal area was 37 m2 haâ1 and the dominant height was about 15 m. After the thinning, the basal area was 27 m2 haâ1. Spruces were thinned from below, but both small and large pines were removed. The second thinning was 8 years later and much heavier: the stand basal area was decreased from 35 m2 haâ1 to 18 m2 haâ1 by removing both small and large pines and spruces. When the optimal two-thinning regime was compared to the regime presented by Forest Centre Tapio, the loss of SEV was about 30% (6070 FIM haâ1) in the case of thinnings from below, and about 20% (7250 FIM haâ1) in the case of thinnings from above.