Differences between students’ PISA reading literacy scores and grading for mother tongue and literature at school : A geostatistical analysis of the Finnish PISA 2009 data

Peer reviewe

Havusekametsästä todelliseen suunnitteluun

Tieteen tor

Effect of species composition on economic return in a mixed stand of Norway spruce and Scots pine.

The effect of species mixture was studied in a mixed stand of Norway spruce and Scots pine by simulating around 100 different treatment schedules during the rotation in a naturally regenerated even-aged stand located on a site of medium fertility in North Karelia, Finland. Both thinning from below and thinning from above were applied. Optimum rotations were determined by maximising the net present value calculated to infinity and different treatment schedules were compared with the net present value over one rotation as per rotation applied. In the optimum treatment programme, the proportion of pines was decreased by half of the basal area in the first thinning stage and by the end of the rotation to about one third. In thinning from above, the proportion of pines can be maintained at a slightly higher level. It is economically profitable to maintain the growing stock capital at approximately the level recommended by Forest Centre Tapio, a semi-governmental forestry authority. With non-optimum species composition, the loss in net present value over one rotation can be about 10% in thinning from below and about 20% in thinning from above

Optimizing thinnings and rotation of Scots pine and Norway spruce mixtures

The study describes a simulation-optimization system which uses spatial models for di-ameter 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 ex-pectation 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 m2ha–1 and the dominant height was about 15 m. After the thinning, the basal area was 27 m2ha–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 m2ha–1 to 18 m2ha–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

Oppilaiden ilmastonmuutososaamisen suhde heidän käsityksiinsä omasta ympäristötietoisuudesta ja -optimismista

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PISA ja TIMSS : Numero- ja sanaleikit kunniaan ja kirjat kulumaan

nonPeerReviewe