Articles by Birger Solberg

The usefulness of forest sector models in forest policy analysis is discussed, mainly based on experiences from Norway. Forest sector modelling is contrasted to two alternative approaches: (i) Intuitive, verbal analysis, and (ii) econometric models. It is concluded that forest sector models, properly developed in contact with the policy makers, should be of considerable value in forest policy analysis.

• Solberg, E-mail: bs@mm.unknown

Forestry and forest industries are important for regional income and employment in Norway as well as in most North European countries, but few studies exist about factors affecting the timber supply at regional level. The main objective of this study is to estimate aggregated regional timber supply elasticities for six regions in Norway. Thereby we also test for regional differences, focusing on wood prices, standing stock volume and interest rate as explanatory variables. We have used three different statistical models (fixed and random effects panel models and first difference models) on regional data from the Norwegian forest inventory on standing volume and official statistics on harvested volumes, interest rate and prices of sawlogs and pulpwood for the period 1996–2016. Statistically significant different price elasticities are found in 12 out of total 15 pairs of regions. The price elasticity was lower and the volume elasticity higher in the western region compared to the other regions. The first difference models are best with respect to specification tests. The use of region specific price elasticities gives slightly better fit for the panel data models than using a uniform price parameter. The results show that the econometric specification influence the parameter values, and it is thus complicated to directly compare results in different timber supply studies. Regional differences in timber supply are important to consider.

• Rørstad, Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Norway E-mail: per.kristian.rorstad@nmbu.no
• Solberg, Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Norway E-mail: birger.solberg@nmbu.no
• Trømborg, Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Norway E-mail: erik.tromborg@nmbu.no

• Raymer, Norwegian University of Life Sciences, Department of Ecology and Natural Resource Management, P.O. Box 5003, N-1432 Ås, Norway E-mail: akr@nn.no
• Gobakken, Norwegian University of Life Sciences, Department of Ecology and Natural Resource Management, P.O. Box 5003, N-1432 Ås, Norway E-mail: terje.gobakken@umb.no
• Solberg, Norwegian University of Life Sciences, Department of Ecology and Natural Resource Management, P.O. Box 5003, N-1432 Ås, Norway E-mail: bs@nn.no

• Rørstad, Norwegian University of Life Sciences, Dept of Ecology and Natural Resource Management, Ås, Norway E-mail: per.kristian.rorstad@umb.no
• Trømborg, Norwegian University of Life Sciences, Dept of Ecology and Natural Resource Management, Ås, Norway E-mail: et@nn.no
• Bergseng, Norwegian University of Life Sciences, Dept of Ecology and Natural Resource Management, Ås, Norway E-mail: eb@nn.no
• Solberg, Norwegian University of Life Sciences, Dept of Ecology and Natural Resource Management, Ås, Norway E-mail: bs@nn.no

• Lindstad, Norwegian University of Life Sciences, Department of Ecology and Natural Resource Management, Ås, Norway E-mail: berit.lindstad@umb.no
• Solberg, Norwegian University of Life Sciences, Department of Ecology and Natural Resource Management, Ås, Norway E-mail: bs@nn.no

This study compares the responses of two Swedish 5-year predictive stand-level functions with the observed responses in 721 fertilization experiment plots in Norway fertilized with nitrogen (N). All plots are single-species consisting of Norway spruce (Picea abies (L.) H. Karst.) or Scots pine (Pinus sylvestris L.) fertilized with ammonium nitrate (AN) or urea. The correlations between the observed and the two predicted responses were 0.34–0.40 for all plots taken together. One response function performed well on average, but underestimated the response in pine plots and overestimated the response in spruce plots. The second function overpredicted the response on the full dataset, in spruce plots and old forest, but performed well in pine plots. Both functions overestimated the growth response in high-productive plots. Higher N deposition in Norway than in Sweden may count for parts of the deviations. Testing of fertilization functions on new datasets is rare, but important part of the evaluation of functions. As the functions are not well fit for predicting the growth response in spruce and high-productive plots in our sample, new functions that include N deposition are welcome.

• Sjølie, Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, NO-1432 Ås, Norway E-mail: hanne.sjolie@nmbu.no
• Sørlie, Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, NO-1432 Ås, Norway E-mail: hans.asbjorn.sorlie@slf.dep.no
• Tveite, Norwegian Forest and Landscape Institute, P.O. Box 115, NO-1431 Ås, Norway E-mail: bjorn.tveite@skogoglandskap.no
• Solberg, Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, NO-1432 Ås, Norway E-mail: birger.solberg@nmbu.no