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dc.contributor.authorPukkala, Timo
dc.contributor.authorHanssen, Kjersti Holt
dc.contributor.authorAndreassen, Kjell
dc.identifier.citationSilva Fennica. 2019, 53 (3), .nb_NO
dc.description.abstractBased on data from long-term experimental fields with Norway spruce (Picea abies (L.) H. Karst.), we developed new stem taper and bark functions for Norway. Data was collected from 477 trees in stands across Norway. Three candidate functions which have shown good performance in previous studies (Kozak 02, Kozak 97 and Bi) were fitted to the data as fixed-effects models. The function with the smallest Akaike Information Criterion (AIC) was then chosen for additional analyses, fitting 1) site index-dependent and 2) age-dependent versions of the model, and 3) fitting a mixed-effects model with tree-specific random parameters. Kozak 97 was found to be the function with the smallest AIC, but all three tested taper functions resulted in fairly similar predictions of stem taper. The site index-dependent function reduced AIC and residual standard error and showed that the effect of site index on stem taper is different in small and large trees. The predictions of the age-independent and age-dependent models were very close to each other. Adding tree-specific random parameters to the model clearly reduced AIC and residual variation. However, the results suggest that the mixed-effects model should be used only when it is possible to calibrate it for each tree, otherwise the fixed-effects Kozak 97 model should be used. A model for double bark thickness was also fitted as fixed-effects Kozak 97 model. The model behaved logically, predicting larger relative but smaller absolute bark thickness for small trees.nb_NO
dc.rightsNavngivelse-DelPåSammeVilkår 4.0 Internasjonal*
dc.subjectPicea abiesnb_NO
dc.subjectForest managementnb_NO
dc.subjectKozak modelnb_NO
dc.subjectVariable-exponent taper functionnb_NO
dc.titleStem taper and bark functions for Norway spruce in Norwaynb_NO
dc.typeJournal articlenb_NO
dc.typePeer reviewednb_NO
dc.subject.nsiVDP::Landbruks- og Fiskerifag: 900nb_NO
dc.source.journalSilva Fennicanb_NO
dc.relation.projectNorges forskningsråd: 281140nb_NO
cristin.unitnameDivisjon for skog og utmark

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Navngivelse-DelPåSammeVilkår 4.0 Internasjonal
Except where otherwise noted, this item's license is described as Navngivelse-DelPåSammeVilkår 4.0 Internasjonal