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Acta Forestalia Fennica
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Articles containing the keyword 'validation'
Category : Research article
article id 1013,
category
Research article
Nils Fahlvik,
Björn Elfving,
Peder Wikström.
(2014).
Evaluation of growth functions used in the Swedish Forest Planning System Heureka.
Silva Fennica
vol.
48
no.
2
article id 1013.
https://doi.org/10.14214/sf.1013
Highlights:
Growth models based on historical growth data gave reliable growth predictions up to the century shift; Detailed single tree growth models had lower precision for estimation of total growth than one single stand-based model; The prediction error was in average about 15% and did not increase with extended prediction period.
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The performance of growth models implemented in the Swedish Forest Planning System Heureka was evaluated. Four basal area growth models were evaluated by comparing their predictions to data from five-year growth records for 1711 permanent sample plots of the National Forest Inventory (NFI-data). Also, two alternative implementations of Heureka, including a combined stand- and tree-level basal area growth model and a single tree-level model, respectively, were evaluated using data from 57 blocks in a thinning experiment (GG-data) involving Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst) in which the trees were monitored for 30 years after the first thinning. The predicted volume growth was also compared to observed values. Growth models based on data from 1970’s and 1980’s overestimated growth in the NFI test plots from the early 2000’s by about 3%. Stand-level models had larger precision than tree-level models. Basal area growth was underestimated in dense NFI-plots and overestimated in non-thinned GG-plots, illustrating an un-solved modelling problem. Basal area growth was overestimated by 2–5% also in the GG-plots over the whole observation period. Volume growth was however accurately predicted for pine and underestimated by 2% for spruce. The relative prediction error did not increase with increasing length of prediction period. Thinning response models calibrated with GG-data worked well in the total application and produced growth levels for different thinning alternatives in line with observations.
-
Fahlvik,
Department of Southern Swedish Forest Research Centre, Swedish University of Agricultural Sciences, P.O. Box 49, SE-230 53 Alnarp, Sweden
E-mail:
nils.fahlvik@slu.se
- Elfving, Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden E-mail: bjorn.elfving@slu.se
- Wikström, Peder Wikström Skogsanalys AB, c/o Peder Wikström, Huldrans väg 1, SE-907 52 Umeå, Sweden E-mail: peder.wikstrom@slu.se
article id 418,
category
Research article
Tron Eid.
(2004).
Testing a large-scale forestry scenario model by means of successive inventories on a forest property.
Silva Fennica
vol.
38
no.
3
article id 418.
https://doi.org/10.14214/sf.418
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Modellers of large-scale forestry scenario models face numerous challenges. Information and sub-models from different disciplines within forestry, along with statistical and mathematical methodology, have to be considered. The individual biological sub-models (i.e. models for recruitment, growth and mortality) applied in large-scale forestry scenario models are in general well documented and extensively evaluated. However, evaluations by means of full-scale comparisons of observed and predicted values for continuous forest areas, where the totality of the large-scale forestry scenario model including interactions between sub-models and other parts of the model, are considered, have rarely been seen. The aim of the present work was to test the totality of the Norwegian large-scale forestry scenario model AVVIRK-2000, and thereby evaluate the applicability of the model for use in management planning. The test was done by means of successive inventories and accurate recordings of treatments over a period of 30 years for a property comprising 78.5 ha forest-land. Seen in the perspective of management planning, the differences between observed and predicted values for potential harvest level, growing stock and growth were small, e.g. a difference between observed growing stock in year 2000 and growing stock in the same year predicted from 1970 of 2.6%. The model may therefore be applied for practical purposes without any fundamental changes or calibrations of the biological model basis. However, the present test should be seen as an example that failed to falsify the model, rather than a final validation. As long as the model is in practical use, further evaluations should continue and subsequent possible calibrations should be performed.
-
Eid,
Agricultural University of Norway, Dept of Ecology and Natural Resource Management, P.O. Box 5003 NO-1432 Ås, Norway
E-mail:
tron.eid@ina.nlh.no
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.
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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
https://orcid.org/0000-0001-8811-152X
E-mail:
christoph.kogler@boku.ac.at
-
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
http://orcid.org/0000-0002-5812-4415
E-mail:
peter.rauch@boku.ac.at
Category : Research note
article id 228,
category
Research note
Aku Riihelä,
Terhikki Manninen.
(2008).
Measuring the vertical albedo profile of a subarctic boreal forest canopy.
Silva Fennica
vol.
42
no.
5
article id 228.
https://doi.org/10.14214/sf.228
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The validation of airborne and satellite-derived albedo measurements suffers from the fact that the surface albedo of forest is difficult to measure in-situ over large areas. The goal of this study is to examine whether or not the estimation of the surface albedo of a forest stand from ground level measurements is possible. In addition, knowledge about the vertical behavior of albedo, and therefore transmitted solar radiation, is important in the modeling of interactions of sunlight with the forest canopy. Such modeling is useful for forest growth estimations among other things. To achieve these goals, an albedometer set-up capable of vertical albedo profiling has been used to obtain data from a boreal forest stand in Northern Finland during periods in summer 2006 and winter 2007. The results show a strong relationship between the data and fitted power-law regression curves. Power-law regression fits best likely because of the radiation transmission characteristics of boreal forest.
-
Riihelä,
Finnish Meteorological Institute, P.O. Box 503, FI-00200 Helsinki, Finland
E-mail:
aku.riihela@fmi.fi
- Manninen, Finnish Meteorological Institute, P.O. Box 503, FI-00200 Helsinki, Finland E-mail: tm@nn.fi
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