%0 Research article
%T Optimizing thinnings and rotation of Scots pine and Norway spruce mixtures
%A Vettenranta, Jouni
%A Miina, Jari
%D 1999
%J Silva Fennica
%V 33
%N 1
%R doi:10.14214/sf.671
%U https://silvafennica.fi/article/671
%X 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 ha–1) 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  ha–1 and the dominant height was about 15 m. After the thinning, the  basal area was 27 m2 ha–1. 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  ha–1 to 18 m2 ha–1 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 ha–1) in the case of thinnings from below, and about 20% (7250 FIM  ha–1) in the case of thinnings from above.