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Silva Fennica 1926-1997
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Articles by Birger Solberg

Category: Research article

article id 109, category Research article
Ann Kristin Raymer, Terje Gobakken, Birger Solberg. (2011). Optimal forest management with carbon benefits included. Silva Fennica vol. 45 no. 3 article id 109. https://doi.org/10.14214/sf.109
In this paper, we analyse how optimal forest management of even aged Norway spruce changes when economic values are placed on carbon fixation, release, and saved greenhouse gas emissions from using wood instead of more energy intensive materials or fossil fuels. The analyses are done for three different site qualities in Norway, assuming present climate and with a range of CO2 prices and real rates of return. Compared to current recommended management, the optimal number of plants per ha and harvest age are considerably higher when carbon benefits are included, and increase with increasing price on CO2. Furthermore, planting becomes more favourable compared to natural regeneration. At the medium site quality, assuming 2% p.a. real rate of return and 20 euros per ton CO2, optimal planting density increases from 1500 per ha to 3000 per ha. Optimal harvest age increases from 90 to 140 years. Including saved greenhouse gas emissions when wood is used instead of more energy intensive materials or fossil fuels, i.e. substitution effects, does not affect optimal planting density much, but implies harvesting up to 20 years earlier. The value of the forest area increases with increasing price on CO2, and most of the income is from carbon. By using the current recommended management in calculations of carbon benefit, our results indicate that the forest’s potential to provide this environmental good is underestimated. The study includes many uncertain factors. Highest uncertainty is related to the accuracy of the forest growth and mortality functions at high stand ages and densities, and that albedo effects and future climate changes are not considered. As such, the results should be viewed as exploratory and not normative.
  • Raymer, Norwegian University of Life Sciences, Department of Ecology and Natural Resource Management, P.O. Box 5003, N-1432 Ås, Norway ORCID ID:E-mail:
  • Gobakken, Norwegian University of Life Sciences, Department of Ecology and Natural Resource Management, P.O. Box 5003, N-1432 Ås, Norway ORCID ID:E-mail: terje.gobakken@umb.no (email)
  • Solberg, Norwegian University of Life Sciences, Department of Ecology and Natural Resource Management, P.O. Box 5003, N-1432 Ås, Norway ORCID ID:E-mail:
article id 141, category Research article
Per Kristian Rørstad, Erik Trømborg, Even Bergseng, Birger Solberg. (2010). Combining GIS and forest modelling in estimating regional supply of harvest residues in Norway. Silva Fennica vol. 44 no. 3 article id 141. https://doi.org/10.14214/sf.141
New and ambitious targets for renewable energy production put attention to increased supply of biomass. Harvest residues are only to a limited extent demanded by the traditional forest industries and represent an unutilized resource for increased production of renewable energy in Norway. The overall objective of this paper is to study how GIS and forest modelling can be combined to improve estimates of the supply of harvest residues, taking different environmental and economic constraints into consideration. The analyses are based on a case study of a forest area of more than 40 000 ha in Southern Norway divided into about 500 private forest properties. The study was carried out by computations of timber harvest using the forestry scenario model SGIS based on extensive forest inventory data at stand level. In the studied area energy utilization of harvest residues is not profitable below an energy price of about EUR 3.2/GJ (NOK 0.10 /kWh) when the distance from roadside to industry is 20 km. Above this level supply increases rapidly over a rather narrow price range and is nearly inelastic above EUR 4.1/GJ (NOK 0.12/kWh). We did not find significant negative shifts in the residues supply caused by changes in location of roundwood harvest over time. Exclusion of collection from stands with a site index (H40) below 14 reduced the potential supply of residues by 16–27%. The optimisation method combined selection of exogenous variables in order to map observed harvesting level and is probably the best approach to map future harvest.
  • Rørstad, Norwegian University of Life Sciences, Dept of Ecology and Natural Resource Management, Ås, Norway ORCID ID:E-mail: per.kristian.rorstad@umb.no (email)
  • Trømborg, Norwegian University of Life Sciences, Dept of Ecology and Natural Resource Management, Ås, Norway ORCID ID:E-mail:
  • Bergseng, Norwegian University of Life Sciences, Dept of Ecology and Natural Resource Management, Ås, Norway ORCID ID:E-mail:
  • Solberg, Norwegian University of Life Sciences, Dept of Ecology and Natural Resource Management, Ås, Norway ORCID ID:E-mail:
article id 167, category Research article
Berit H. Lindstad, Birger Solberg. (2010). Assessing national compliance with international forest policy processes – the role of subjective judgments. Silva Fennica vol. 44 no. 1 article id 167. https://doi.org/10.14214/sf.167
Several international policy processes with sustainable forest management (SFM) as a common goal have emerged during the past two decades. Based on an empirical study from Norway, this paper analyses the role of subjective judgments in assessing national compliance with three international forest policy processes, and the implications for determination of the effects of these processes. The Expanded Programme of Work on Forest Biological Diversity, the Ministerial Conference on the Protection of Forests in Europe and the United Nations Forum on Forests, including its predecessors, collectively provide more than 600 recommendations for SFM. While it is nothing new that SFM encompasses value questions, this paper is a systematic review of where in a process of assessing national compliance the role of judgments is most profound. The paper shows that the multiple objectives of the forest recommendations, references to national circumstances and provisions for stakeholder involvement lead to differing opinions about the degree of conformity between international recommendations and national situation, i.e. compliance. These differing opinions mean different prospects for the international processes to have effects, because only implementation, or active responses to international recommendations, constitutes effects. The roles of judgments and values are recommended topics for further investigation. Factors influencing how compliance is assessed, and consequently the degree to which implementation is deemed necessary, require specific attention. Due consideration to substantive and methodological choices in determining national changes and in separation of other sources of influence will provide a better basis for informed discussion of compliance with and effects of international forest-related policy processes.
  • Lindstad, Norwegian University of Life Sciences, Department of Ecology and Natural Resource Management, Ås, Norway ORCID ID:E-mail: berit.lindstad@umb.no (email)
  • Solberg, Norwegian University of Life Sciences, Department of Ecology and Natural Resource Management, Ås, Norway ORCID ID:E-mail:

Category: Research note

article id 1330, category Research note
Hanne K. Sjølie, Hans Asbjørn Kårstad Sørlie, Bjørn Tveite, Birger Solberg. (2015). The performance of two Swedish N fertilization functions evaluated on data from Norwegian fertilization experiments. Silva Fennica vol. 49 no. 4 article id 1330. https://doi.org/10.14214/sf.1330
Highlights: The performance of two predictive Swedish fertilization growth response functions was assessed on data from Norwegian fertilization experiments; One function performed well on the full dataset, but overpredicted the growth response in spruce plots and underpredicted in pine plots; The second function performed well in pine stands, but overestimated the growth response in spruce and in total.

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

Category: Article

article id 5301, category Article
Birger Solberg. (1986). Forest sector simulation models as methodological tools in forest policy analysis. Silva Fennica vol. 20 no. 4 article id 5301. https://doi.org/10.14214/sf.a27757

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, ORCID ID:E-mail:

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