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Articles containing the keyword 'simulation model'

Category : Article

article id 5591, category Article
Egbert Beuker, Seppo Kellomäki, Marja Kolström. (1996). Changes in wood production of Picea abies and Pinus sylvestris under a warmer climate: comparison of field measurements and results of a mathematical model. Silva Fennica vol. 30 no. 2–3 article id 5591. https://doi.org/10.14214/sf.a9236
Keywords: Pinus sylvestris; climate change; Picea abies; simulation model; global warming; provenance trials
Abstract | View details | Full text in PDF | Author Info

To project the changes in wood production of Norway spruce (Picea abies (L.) H. Karst.) and Scots pine (Pinus sylvestris L.) in Finland as a result of climate change, two separate studies were made. The first study, at the Faculty of Forestry, University of Joensuu, based its projections on mathematical models; the second one, at the Finnish Forest Research Institute, based projections on measurements of wood production in two series of aged provenance experiments. The results of the two studies were similar for both species: after a 4°C increase of the annual mean temperature a drastic increase in wood production in northern Finland, but little effect, or even some decrease in the southern part of the country. However, the assumptions used in the two studies differed. One important difference was that in the models the temperature is assumed to be increasing gradually over the years, whereas in the provenance experiments, climate changed immediately when the seedlings were transferred to the planting sites. Another problem with the provenance experiments is that when material is moved in a north-south direction in Finland, not only temperature but also photoperiod changes markedly. To compare these two studies, site factors (e.g. soil type, temperature, precipitation) and silvicultural factors (e.g. plant spacing, survival, time of thinning, thinning intensity) from the provenance experiments were included a variable in the mathematical models.

  • Beuker, E-mail: eb@mm.unknown (email)
  • Kellomäki, E-mail: sk@mm.unknown
  • Kolström, E-mail: mk@mm.unknown
article id 5468, category Article
Seppo Kellomäki, Heikki Hänninen, Taneli Kolström, Risto Lauhanen, Ulla Mattila, Brita Pajari, Hannu Väisänen. (1992). A simulation model for the succession of the boreal forest ecosystem. Silva Fennica vol. 26 no. 1 article id 5468. https://doi.org/10.14214/sf.a15626
Keywords: succession; gap dynamics; ecosystems; simulation models; forest ecology
Abstract | View details | Full text in PDF | Author Info

A model for the succession of the forest ecosystem is described. The growth and development of trees and ground cover are controlled by temperature and light conditions and the availability of nitrogen and water. In addition, the effects of the annual cycle of trees including the risk of frost damage, wild fire, and wind damages are contained in the model as factors which control the survival and productivity of trees. The model also makes it possible to evaluated the risk of insect attack assuming that this risk is inversely related to the growth efficiency of trees.

The PDF includes an abstract in Finnish.

  • Kellomäki, E-mail: sk@mm.unknown (email)
  • Hänninen, E-mail: hh@mm.unknown
  • Kolström, E-mail: tk@mm.unknown
  • Lauhanen, E-mail: rl@mm.unknown
  • Mattila, E-mail: um@mm.unknown
  • Pajari, E-mail: bp@mm.unknown
  • Väisänen, E-mail: hv@mm.unknown
article id 5449, category Article
Timo Pukkala, Taneli Kolström. (1991). Effect of spatial pattern of trees on the growth of Norway spruce stand. Silva Fennica vol. 25 no. 3 article id 5449. https://doi.org/10.14214/sf.a15603
Keywords: Picea abies; thinnings; growth; spatial distribution; simulation models; biological competition
Abstract | View details | Full text in PDF | Author Info

The simulation model consists of a method to generate theoretical Norway spruce (Picea abies (L.) H. Karst.) stands, and a spatial growth model to predict the growth of these stands. The stand generation procedure first predicts the tree diameters from a few stand characteristics and from tree locations. Tree age and height are predicted using spatial models. Spatial growth models were made for both diameter growth and basal area growth. Past growth was used as a predictor in one pair of models and omitted in another pair. The stand generation method and the growth models were utilized in studying the effect of tree arrangement and thinning method on the growth of a Norway spruce stand.

The PDF includes an abstract in Finnish.

  • Pukkala, E-mail: tp@mm.unknown (email)
  • Kolström, E-mail: tk@mm.unknown
article id 5419, category Article
Timo Pukkala, Owen Mubita, Jussi Saramäki. (1990). Management planning system for tree plantations. Silva Fennica vol. 24 no. 2 article id 5419. https://doi.org/10.14214/sf.a15573
Keywords: diameter distribution; plantations; yield model; Zambia; simulation model; Pinus kesiya; timber management planning; multiobjective optimization
Abstract | View details | Full text in PDF | Author Info

The paper presents a simple model of long-term forest management planning in tree plantations. The model is particularly suitable for developing countries where the research resources are limited. The management plan is prepared in two steps. First, one or several treatment schedules are simulated for each calculation unit (age class, compartment, etc.) over the selected planning period. Second, an optimal combination treatment schedules according to the selected objectives and constraints is searched by mathematical programming. The simulation of growth is based on the prediction of the diameter distribution at the desired time point. All stand characteristics are derived from this distribution. The models needed in the yield simulation can be estimated from temporary sample plots. A case study management plan for 13,000 ha of Pinus kesiya (Royle ex Gordon) plantations in Zambia is presented to demonstrate the system.

The PDF includes an abstract in Finnish.

  • Pukkala, E-mail: tp@mm.unknown (email)
  • Mubita, E-mail: om@mm.unknown
  • Saramäki, E-mail: js@mm.unknown
article id 5357, category Article
Heikki Hänninen, Paavo Pelkonen. (1988). Effects of temperature on dormancy release in Norway spruce and Scots pine seedlings. Silva Fennica vol. 22 no. 3 article id 5357. https://doi.org/10.14214/sf.a15514
Keywords: Pinus sylvestris; Norway spruce; Picea abies; Scots pine; bud burst; dormancy release; annual cycle of development; chilling requirement; rest period; simulation model
Abstract | View details | Full text in PDF | Author Info

Models concerning the effects of temperature on dormancy release in woody plants were tested using two-year old seedlings of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst.). Chilling experiments suggest that the rest period has a distinct end point. Before the attainment of this end point high temperatures do not promote bud development towards dormancy release, and after it further chilling does not affect the subsequent bud development. A new hypothesis of dormancy release is suggested on the basis of a comparison between present and earlier findings. No difference in the proportion of growth commencing seedlings were detected between the forcing temperatures of 17°C and 22°C. The rest break of 50% of Norway spruce and Scots pine seedlings required six and eight weeks of chilling, respectively. Great variation in the chilling requirement was found, especially for Scots pine.

The PDF includes an abstract in Finnish.

  • Hänninen, E-mail: hh@mm.unknown (email)
  • Pelkonen, E-mail: pp@mm.unknown
article id 5319, category Article
Heikki Hänninen. (1987). Effects of temperature on dormancy release in woody plants. Silva Fennica vol. 21 no. 3 article id 5319. https://doi.org/10.14214/sf.a15476
Keywords: temperature; bud burst; dormancy; annual cycle of development; dormancy breaking; chilling requirement; rate of development; rest period; simulation model; stage of development
Abstract | View details | Full text in PDF | Author Info

Logical structure of three simulation models and one conceptual model concerning effects of temperature on dormancy release in woody plants was examined. The three basic types of simulation models differed in their underlying assumptions. Contrasting implications of the models were inferred by deduction. With the aid of these implications, the model types can be tested using experiments with continuous and interrupted chilling. Similarly, implications of the conceptual model of rest phases were inferred, by which the model can be tested using experiments with continuous chilling and forcing in multiple temperatures. The possibilities to synthetize the conceptual model with any of the three simulation model types, as well as the biological interpretation of the model variables, were discussed.

The PDF includes an abstract in Finnish.

  • Hänninen, E-mail: hh@mm.unknown (email)
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
Keywords: forest policy; Norway; simulation models; forest sector models; forest policy analysis
Abstract | View details | Full text in PDF | Author Info

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 (email)

Category : Article

article id 7676, category Article
Jussi Saramäki. (1992). A growth and yield prediction model of Pinus kesiya (Royle ex Gordon) in Zambia. Acta Forestalia Fennica no. 230 article id 7676. https://doi.org/10.14214/aff.7676
Keywords: diameter distribution; Weibull function; simulation models; Pinus kesiya; thinning reaction
Abstract | View details | Full text in PDF | Author Info

The study presents a growth and yield prediction model for a Pinus kesiya (Royle ex Gordon) stand by diameter classes. The material consists of temporary sample plots taken from a plantation inventory, of permanent sample plots established in commercial compartments and of an espacement trial. The mean basal area of the stand, variance and skewness of the diameter distribution are predicted. From these variables the parameters of the Weibull function are derived. Site class is assumed to be known or is calculated from measured information. Mortality is also predicted by estimating the number and mean size of dead trees. Thinnings are defined by the number of trees removed and by their relative size. If measured tree level data at the initial situation is available it can be utilized in the predictions, however, simulations can also be performed with stand level information. The minimum information needed for the prediction is planting density, site class as well as the times and removals of thinnings.

The calculations show that by decreasing the planting density of P. Kesiya from the present 1,330 stems/ha or by conducting early precommercial thinning both the relative and absolute amount of large sawlogs in the total production increase. An increase in the present planting density only slightly increases total yield. It is obvious that the presently recommended rotation of 25 years is too short for producing large sawlogs, especially on poor sites. This rotation period is suitable for small sawlog production while for pulpwood regimes shorter rotation periods can be used. If thinnings are done before the maximum current annual growth is reached stands will react well, but later on the ability to respond to thinnings decreases rapidly. Thinnings from below accelerates the production of large sawlogs more than thinning from above or systematic thinning. If all sawlog sizes are considered no great differences between thinning type exist. The study recommends different thinning regimes according to site class. Separate programs are recommended for the production of sawlogs and pulpwood.

The used thinning reaction model needs refinement and further studies with annual measured thinning trial material.

The PDF includes a summary in Finnish.

  • Saramäki, E-mail: js@mm.unknown (email)

Category : Research article

article id 671, category Research article
Jouni Vettenranta, Jari Miina. (1999). Optimizing thinnings and rotation of Scots pine and Norway spruce mixtures. Silva Fennica vol. 33 no. 1 article id 671. https://doi.org/10.14214/sf.671
Keywords: mixed forests; optimal treatments; simulation models; Hooke and Jeeves’ method; thinning types
Abstract | View details | Full text in PDF | Author Info
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.
  • Vettenranta, Kivirinnanpolku 4, FIN-40950 Muurame, Finland E-mail: vettenr@cc.joensuu.fi (email)
  • Miina, Faculty of Forestry, University of Joensuu, P.O. Box 111, FIN-80101 Joensuu, Finland E-mail: jm@nn.fi

Category : Review article

article id 9984, category Review article
Christoph Kogler, Peter Rauch. (2018). Discrete event simulation of multimodal and unimodal transportation in the wood supply chain: a literature review. Silva Fennica vol. 52 no. 4 article id 9984. https://doi.org/10.14214/sf.9984
Keywords: logistics; supply chain management; forest products industry; decision support systems; validation and verification of simulation models; resilient risk management
Highlights: Focus on discrete event simulation, wood supply chain and multimodal transport; Analyses of 12 review articles and a core of 32 research papers, complemented by 48 related ones; Research focus from unimodal to multimodal transport to build efficient, resilient, green and socially sustainable supply chains; Development of robust risk management considering supply risks, demand risks and external risks is needed.
Abstract | Full text in HTML | Full text in PDF | Author Info

This review systematically analyses and classifies research and review papers focusing on discrete event simulation applied to wood transport, and therefore illustrates the development of the research area from 1997 until 2017. Discrete event simulation allows complex supply chain models to be mapped in a straightforward manner to study supply chain dynamics, test alternative strategies, communicate findings and facilitate understanding of various stakeholders. The presented analyses confirm that discrete event simulation is well-suited for analyzing interconnected wood supply chain transportation issues on an operational and tactical level. Transport is the connective link between interrelated system components of the forest products industry. Therefore, a survey on transport logistics allows to analyze the significance of entire supply chain management considerations to improve the overall performance and not only one part in isolation. Thus far, research focuses mainly on biomass, unimodal truck transport and terminal operations. Common shortcomings identified include rough explanations of simulation models and sparse details provided about the verification and validation processes. Research gaps exist concerning simulations of entire, resilient and multimodal wood supply chains as well as supply and demand risks. Further studies should expand upon the few initial attempts to combine various simulation methods with optimization.

  • Kogler, Institute of Production and Logistics, Department of Economics and Social Sciences, University of Natural Resources and Life Sciences, Vienna, Feistmantelstrasse 4, A-1180 Vienna, Austria ORCID https://orcid.org/0000-0001-8811-152X E-mail: christoph.kogler@boku.ac.at (email)
  • Rauch, Institute of Production and Logistics, Department of Economics and Social Sciences, University of Natural Resources and Life Sciences, Vienna, Feistmantelstrasse 4, A-1180 Vienna, Austria ORCID http://orcid.org/0000-0002-5812-4415 E-mail: peter.rauch@boku.ac.at

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