Articles containing the keyword 'location'

The rule-based formal language of "stochastic sensitive growth grammars" was designed to describe algorithmically the changing morphology of forest trees during their lifetime under the impact of endogenous and exogenous factors, and to generate 3-D simulations of tree structures in a systematic manner. The description in the form of grammars allows the precise specification of structural models with functional components. These grammars (extended L-systems) can be interpreted by the software GROGRA (Growth grammar interpreter) yielding time series of attributed 3-D structures representing plants. With some recent extensions of the growth-grammar language (sensitive functions, local variables) it is possible to model environmental control of shoot growth and some simple allocation strategies, and to obtain typical competition effects in tree stands qualitatively in the model.

• Kurth, E-mail: wk@mm.unknown
• Sloboda, E-mail: bs@mm.unknown

A metabolic model of height growth and site index is derived from a parametrization of the annual carbon balance of a tree. The parametrization is based on pipe-model theory. Four principal variants of the height-growth model correspond to four combinations of assumptions regarding carbon allocation: (a) the apical shoot is autonomous or (b) it is not; and (A) the specific rate of elongation of a shoot equals that of a woody root or (B) it does not. The bB model is the most general as it includes the aA, bA, and aB models as special cases. If the physiological parameters are constant, then the aA model reduces to the form of the Mitscherlich model and the bA model to the form of a Bertalanffy model. Responses of height growth to year-to-year variation in atmospheric conditions are rendered through adjustments of a subset of the model's parameters, namely, the specific rate of production of carbon substrate and three specific rates of maintenance respiration. As an example, the effect of the increasing atmospheric concentration of CO₂ on the time-course of tree height of loblolly pine (Pinus taeda) is projected over 50-year span from 1986. Site index is predicted to increase and, more importantly, the shape of the site-index curve is predicted to change.

• Valentine, E-mail: hv@mm.unknown

Process-based tree growth models are recognized to be flexible tools which are valuable for investigating tree growth in relation to changing environment or silvicultural treatments. In the context of forestry, we address two key modelling problems: allocation of growth which determines total wood production, and distribution of wood along the stem which determines stem form and wood quality. Growth allocation and distribution are the outcome of carbon translocation, which may be described by the Munch theory. We propose a simpler gradient process to describe the carbon distribution in the phloem of conifers. This model is a reformulation of a carbon diffusion-like process proposed by Thornley in 1972. By taking into account the continuity of the cambium along the stem, we obtain a one-dimensional reaction-diffusion model which describes both growth allocation between foliage, stem and roots, and growth distribution along the stem. Distribution of wood along the stem is then regarded as an allocation process at a smaller scale. A preliminary sensitivity analysis is presented. The model predicts a strong relationship between morphology and foliage-root allocation. It also suggests how empirical data, such as stem analysis, could be used to calibrate and validate allocation rules in process-based growth models.

• Deleuze, E-mail: cd@mm.unknown
• Houllier, E-mail: fh@mm.unknown

Change in dry matter partitioning, ¹⁴C-incorporation, and sink ¹⁴C-activity of 1.5-year-old Scots pine (Pinus sylvestris L.) seedlings grown in growth chamber conditions were studied during a 91-day experiment. On five sampling dates, seedlings were labelled with ¹⁴CO₂ and whole-plant allocation patterns were determined. Intensively growing shoots modified the dry matter partitioning: during shoot growth the proportion of roots decreased but after that it increased. Based on their large proportion of dry matter, the needles (excluding current needles) were the strongest sink of carbon containing 40% of the incorporated ¹⁴C. Despite their small initial sink size, the elongating shoots (current main shoot + current branch) and their needles were the second strongest sink (30–40% of the total ¹⁴C) which reflects their high physiological activity. The proportion of ¹⁴C in the current year’s main shoot increased during shoot growth but decreased as the growth began to decline after 70 days. 10–20% of the total assimilated ¹⁴C was translocated to the roots. Laterals above 2nd order were the strongest sink in the root system, containing twice as much ¹⁴C as the other roots together. Alternation between shoot and root growth can be seen clearly: carbon allocation to roots was relatively high before and after the period of intensive shoot growth. Changes in root sink strength resulted primarily from changes in root sink activity rather than sink size.

• Lippu, E-mail: jl@mm.unknown

Crown characteristics and the distribution of three years’ (1986–88) biomass production of 20 pendulous Norway spruce (Picea abies f. pendula (Lawson) Sylvén) trees with heritable narrow crown and 15 normal-growned spruces (Picea abies (L.) H. Karst.) were studied in a 19-year-old mixed stand.

The form of the crown is conical in normal-crowned trees, columnar and narrow in pendulous trees. The partitioning of aboveground biomass to stems during the studied 3-year period was significantly higher in pendulous (0.281) than in normal-crowned trees (0.255) and also the ratio between growth of stemwood and growth of needle biomass during three years was higher in pendulous trees (0.67 g g^-1) than in normal-crowned trees (0.52 g g^-1). The needle biomass was distributed higher in the crown in pendula than in normal-crowned trees and they had a higher needle biomass/branchwood biomass ratio than normal trees. The difference in harvest increment between the two crown types are mostly due to the significantly lower branchwood biomass values in pendulous than in normal-crowned trees. The higher needle ’efficiency’ in pendulous trees is probably connected with high partitioning of needle biomass to the upper part of the crown in pendulous trees.

The PDF includes an abstract in Finnish.

• Pulkkinen, E-mail: pp@mm.unknown

A model was constructed, the aim of which was to predict growth under conditions where air pollutants are present. The model is based on photosynthesis and on the allocation of photosynthetic products for growth. It is assumed that air pollutants released during energy production mainly affect photosynthesis in two ways: 1) directly by injuring the photosynthetic mechanism, and 2) indirectly by leaching nutrients. The two ways were studied empirically in order to identify a sub-model for the photosynthesis of a plant exposed to air pollutants. 

The stand model will be applied to two purposes. The present stage of forests in Finland is compared with the simulated state based on the assumption that no pollutants are present. In addition, the decrease in forest yield under different conditions derived from predictions about long-range pollutant transport in Europe is analysed.

• Mäkelä, E-mail: am@mm.unknown
• Hari, E-mail: ph@mm.unknown
• Kellomäki, E-mail: sk@mm.unknown

The proportions of needle and wood in current-year shoots in crown systems of young Scots pine (Pinus sylvestris L.) trees was studied. The proportion of needles out of the total shoot biomass increased according to the increasing number of the whorl counted from the apex. In the lower part of the crown system the needle biomass of newly-formed shoots was 50–60 fold compared to that of wood and bark biomass. In the upper part of the crown system the same ratio was 1–2. The variation in ratio between needle and wood biomass was whorl-specific and independent of tree class. The magnitude of the ratio was not related to the position of the tree in the stand nor to the prevailing light conditions within the state.

The PDF includes a summary in Finnish.

• Mäkelä, E-mail: am@mm.unknown
• Hari, E-mail: ph@mm.unknown
• Kellomäki, E-mail: sk@mm.unknown

About one million hectares of forests are fertilized annually in Finland. The goal of the present study was to find out, by means of calculations, how the profitability of forest fertilization varies with variations in the stage of development of tree crops, the quality of the site and its geographical location. Calculations concerned bot fertilization of forests in mineral soil sites and in drained peatlands. The study is a part of a larger project concerning the order of profitability of different forest improvement measures in different conditions. The problems dealt with in this study were approached from the point of view of national economy.

On the basis of two empirical materials it is shown that there is a high correlation between the stand growth percentages before and after the fertilization. Applying the results to existing yield tables the authors calculate benefit/cost ratios showing the stage of development of the stand, the quality of the site and its geographical location. According to the results, fertilization is more profitable in sites of medium fertility than on poor sites. Profitability decreases rather fast from south to north and with decreasing timber prices. 

The PDF includes a summary in English.

• Keltikangas, E-mail: mk@mm.unknown
• Seppälä, E-mail: ks@mm.unknown

One forest drainage undertaking in Finland often consists of woodlots belonging to several owners, and over hundred owners may be involved. In the present paper a method for allocation the costs to different owners in a joint drainage undertaking is worked out. The problem has been emphasised by the new Waterways Law, which enables also such drainage projects to be undertaken to which some of the land owners oppose. In those cased the costs must be allocated according to the benefit driven by each owner from the project.

The method attempts to assess the benefits to be driven from the forest drainage, those costs of the drainage that are joint and thus subjected to allocation, and what is the area affected by drainage as used as a basis for cost allocation.

The joined costs are apportioned in the following manner. The area of peatland adjusted to differences in the benefit obtained by drainage is ascertained by the land holder by multiplying the index number by the corresponding areas. In the case of cultivated agricultural land, also an index showing the need for drainage is used in computing the adjusted area. Each topographic unit in the map is provided with a notation of its apportionment area. Joined costs are allocated to different land owners in relation to their adjusted land areas.

The PDF includes a summary in English.

• Heikurainen, E-mail: lh@mm.unknown
• Keltikangas, E-mail: mk@mm.unknown
• Seppälä, E-mail: ks@mm.unknown

The accompanying collective research report is the result of the research project in 1986–90 between the Finnish Academy and the former Soviet Academy of Sciences. The project was organized around common field work in Finland and in the former Soviet Union, and theoretical analyses of tree growth determining processes. Based on theoretical analyses, dynamic stand growth models were made and their parameters were determined utilizing the field results.

Annual cycle effects the tree growth. Our theoretical approach was based on adaptation to local climate conditions from Lapland to South Russia. The initiation of growth was described as a simple low and high temperature accumulation driven model. The model was linked with long-term temperature data.

Analysis of field measurements of CO₂ exchange showed that irradiance is the dominating factor causing variation in photosynthetic rate in natural conditions during summer. The penetration of irradiance into Scots pine (Pinus sylvestris L.) canopy is a complicated phenomenon. A moderately simple but balanced forest radiation regime sub-model was constructed.

The common field excursions in different geographical regions resulted in a lot of experimental data of regularities of woody structure. The water transport seems to be a good common factor to analyse these properties of tree structure. The produced theoretical and experimental material was utilized in the development of stand growth model that describes the growth and development of Scots pine stands in Finland and the former Soviet Union. The core of the model is carbon and nutrient balances. This means that carbon obtained in photosynthesis is consumed or growth and maintenance and nutrients are taken according to the metabolic need. Since the fundamental metabolic processes are the same in all locations, the same growth model structure can be applied in the large range of Scots pine. The model enables the analysis of geographical differences in the growth of Scots pine. The present approach enables utilization of structural and functional knowledge gained in places of intensive research, in the analysis of growth and development of any stand.

• Hari, E-mail: ph@mm.unknown
• Ross, E-mail: jr@mm.unknown
• Mecke, E-mail: ph@mm.unknown

The aim of this study was to investigate the ecophysiological and morphological characteristics of two salt-tolerant tree species, Eucalyptus camaldulensis Dehn. and Combretum quadrangulare Kurz. A greenhouse experiment with different levels of NaCl salinity (0, 0.5, 1.0, 1.5, and 2.0%) was set up and the results were compared with those of a field study on non-saline and saline soils. The determination of optimum gas exchange and the development and evaluation of photosynthetic models with and without water deficit were also included in this study.

Morphological characteristics under saline conditions showed that shoot height and diameter growth, shoot internode length, root length/biomass, leaf width and length, leaf area, number and biomass, and shoot/root and leaf/root ratios decreased with salinity, while leaf thickness increased with salinity. More growth was allocated to the roots than to the leaf canopy. Ecophysiological studies in laboratory showed that photosynthesis, stomatal conductance and water potential decreased with salinity, while the CO₂ compensation point increased with salinity. Transpiration, dark respiration and photorespiration increased at low salinity but decreased at high salinity levels. In the field study, however, there were no significant differences in stomatal conductance and opening between saline and non-saline soils. Model predictions supported the results of the field measurements. Adaptation to salinity was reflected in an acclimatization of tree structure in the field study. There were both functioning and structural changes of seedlings in the greenhouse experiment

In terms of ecophysiological and morphological characteristics, E. Camaldulensis showed better salt tolerance than C. Quadragulare both in the greenhouse experiment and field study

The PDF includes a summary in Finnish.

• Luangjame, E-mail: jl@mm.unknown

At the beginning of the investigation period the total biomass of the Scots pine (Pinus sylvestris L.) stands on the ordinary sedge pine mire was 48 t/ha. The biomass of the mixed stands of Scots pine and birch (Betula pubescens Erhr.) on the herbrich sedge pine mire was 91 t/ha, out of which 60% was from pine. The biomass of the Norway spruce (Picea abies (L.) H. Karst.) on the Vaccinium-Myrtillus spruce mire was 148 t/ha. The average annual net increment of the stand biomass was 5.8 t/ha in the unfertilized pine stand and 6.7 t/ha in the NPK and micronutrient fertilized one during the six-year investigation period. The corresponding figures in the mixed stand were 7.2 t/ha and 7.6 t/ha. The net increment of the biomass in the unfertilized spruce stand was 6.9 t/ha and in the fertilized 8.4 t/ha. A considerable proportion of the net increment was lost to the ground as litter in all stands.

The nitrogen, phosphorus, potassium, magnesium, iron, manganese, zinc, copper and boron cycles were investigated. The annual nitrogen uptake from the soil was 26–42 kg/ha, that of phosphorus 2.5–3.4 kg/ha, potassium 4.5–12 kg/ha, calcium 12–29 kg/ha, magnesium 2–4 kg/ha, iron 1.4–6.6 kg/ha, manganese less than 2 kg/ha and the other nutrients only some grams. Only part of the fertilized nutrients was fixed in the stand.

The PDF includes a summary in Finnish.

• Finér, E-mail: lf@mm.unknown

Flowering time and characteristics of cones and seed development of Scots pine (Pinus sylvestris L.) plus tree clones originating from various parts of Finland and planted (grafts) in Southern Finland (61° 48’ N, 29° 19’ E) were studied during 1976-1978.

The flowering time (in terms of period unit (p.u.) sums for flowering) of the Scots pine plus tree clones showed characteristics specific to each population and the characteristics appear mainly adapted to the local temperature factor within Finland. Generally, the development of floral organs, cones and seed in the spring and summer seasons also showed a temperature dependence in that the reproductive organs are developed rapidly and/or favourably under higher temperature conditions within its optimum range.

In this respect, establishment of northern Scots pine seed orchards in Central or Southern Finland or an optimum flowering, and a favourable seed development with an optimum physiological reproductive isolation from surrounding Scots pine populations can be justified. Problem arising from the north-south transfer of seed orchards and the significance of trees’ growth rhythm are discussed in connection with tree improvement.

The PDF includes a summary in Finnish.

• Chung, E-mail: mc@mm.unknown

• Jåstad, Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Norway https://orcid.org/0000-0002-1089-0284 E-mail: eirik.jastad@nmbu.no
• Nagel, Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Norway https://orcid.org/0000-0002-3171-0262 E-mail: niels.oliver.nagel@nmbu.no
• Hu, Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Norway https://orcid.org/0000-0003-0001-5993 E-mail: junhui.hu@nmbu.no
• 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

A new method for the co-registration of single tree data in forest stands and forest plots applicable to static as well as dynamic data capture is presented. This method consists of a stem diameter weighted linking algorithm that improves the linking accuracy when operating on diverse diameter stands with stem position errors in the single tree detectors. A co-registration quality metric threshold, Q_T, is also introduced which makes it possible to discriminate between correct and incorrect stem map co-registrations with high probability (>99%). These two features are combined to a simultaneous location and mapping-based co-registration method that operates with high linking accuracy and that can handle sensors with drifting errors and signal bias. A test with simulated data shows that the method has an 89.35% detection rate. The statistics of different settings in a simulation study are presented, where the effect of stem density and position errors were investigated. A test case with real sensor data from a forest stand shows that the average nearest neighbor distances decreased from 1.90 m to 0.51 m, which indicates the feasibility of this method.

• Olofsson, Section of Forest Remote Sensing, Department of Forest Resource Management, Swedish University of Agricultural Sciences, Umeå, Sweden https://orcid.org/0000-0002-2836-2316 E-mail: kenneth.olofsson@slu.se
• Holmgren, Section of Forest Remote Sensing, Department of Forest Resource Management, Swedish University of Agricultural Sciences, Umeå, Sweden https://orcid.org/0000-0002-7112-8015 E-mail: johan.holmgren@slu.se

Due to changes in forest management in various European countries, hardwood forest areas and amounts will increase. Sustainable and individual utilization concepts have to be developed for the upcoming available resource. Studies conclude that there is low potential for hardwoods in the traditional appearance market thus the application areas have to be extended to new structural innovative products. This paper examines the extension to a future laminated beech wood supply network which would be a combination of already existing and new production facilities. For a better future use of hardwood raw materials it is necessary to consider the entire supply chain. This also better shows a total hardwood value chain. Therefore, this paper provides data to the solid hardwood business and develops a mixed integer linear programming to design a laminated beech wood supply network. The model is applied to Austria as the sample region. It covers the important strategic decisions where to locate a downstream facility within the existing production network with the lowest supply network cost. Fourteen scenarios are developed to examine various future network configurations. Results about optimal material flows and used sawmills as well as downstream production facilities are presented in form of material and financial performances. Two optimal laminated beech production locations are determined by the calculated scenarios results, and the impact of a new sawmill is analyzed which is focused on beech.

• Kühle, BOKU - University of Natural Resources and Life Sciences, Vienna, Department of Material Science and Process Engineering, and Renewable Institute of Wood Technology Materials, Konrad-Lorenz-Straße 24, 3430 Tulln, Austria E-mail: skuehle@boku.ac.at
• Teischinger, BOKU - University of Natural Resources and Life Sciences, Vienna, Department of Material Science and Process Engineering, and Renewable Institute of Wood Technology Materials, Konrad-Lorenz-Straße 24, 3430 Tulln, Austria E-mail: alfred.teischinger@boku.ac.at
• Gronalt, BOKU - University of Natural Resources and Life Sciences, Vienna, Department of Economics and Social Sciences, Institute of Production and Logistics, Feistmantelstraße 4, 1180 Vienna, Austria E-mail: manfred.gronalt@boku.ac.at

This work presents the findings of a study concerning variability in the basic density of silver birch (Betula pendula Roth) wood, depending on the geographical location of tree stands, the age and thickness of the trees, the forest habitat type, and interactions between some of these factors. The study was carried out on wood from trees aged approximately 30, 50 and 70 years in 12 forest districts located throughout Poland. In total 4777 wood samples, taken from 306 trees from 51 test plots, were measured. The location, the age of the trees, the thickness of the trees and the forest habitat type, as well as interactions between these factors, proved to have a significant influence on the basic density of silver birch wood. The highest mean values of the basic density of the birch wood were found in Sokołów forest district on the FBF habitat type (549 kg m^–3) and in Giżycko forest district on the FMBF habitat type (548 kg m^–3). For the entire set of examined material, the average values of the basic density of wood increase with tree age. For the examined material originating in FBF and FMBF habitats the average values of basic density showed no significant differences; however, in the cases of the forest districts of Giżycko, Łobez and Rudziniec, significant differences in the analysed property were observed.

• Lachowicz, Department of Forest Utilization, Warsaw University of Life Sciences SGGW, Nowoursynowska 159 02-787 Warsaw, Poland E-mail: hubert.lachowicz@wl.sggw.pl
• Bieniasz, Department of Forest Utilization, Warsaw University of Life Sciences SGGW, Nowoursynowska 159 02-787 Warsaw, Poland E-mail: anna.bieniasz@wl.sggw.pl
• Wojtan, Laboratory of Dendrometry and Forest Productivity, Warsaw University of Life Sciences SGGW, Nowoursynowska 159 02-787 Warsaw, Poland E-mail: rwojtan@wl.sggw.pl

• Lu, Deparment of Forestry, University of Missouri, Columbia, MO, USA E-mail: ml@nn.us
• Nygren, The Finnish Society of Forest Science, P.O. 18, FI-01301 Vantaa, Finland E-mail: pekka.nygren@metla.fi
• Perttunen, Finnish Forest Research Institute, Vantaa, Finland E-mail: jp@nn.fi
• Pallardy, Deparment of Forestry, University of Missouri, Columbia, MO, USA E-mail: sgp@nn.us
• Larsen, Deparment of Forestry, University of Missouri, Columbia, MO, USA E-mail: drl@nn.us

• Qi, Ecole Centrale Paris, Laboratory of Applied Mathematics, Grande Voie des Vignes, 92295 Chatenay-Malabry, France; Institute of Automation, Chinese Academy of Sciences, LIAMA/NLPR, P.O.Box 2728, Beijing, China E-mail: qiruitree@gmail.com
• Letort, Ecole Centrale Paris, Laboratory of Applied Mathematics, Grande Voie des Vignes, 92295 Chatenay-Malabry, France E-mail: vl@nn.fr
• Kang, Institute of Automation, Chinese Academy of Sciences, LIAMA/NLPR, P.O.Box 2728, Beijing, China E-mail: mk@nn.cn
• Cournède, Ecole Centrale Paris, Laboratory of Applied Mathematics, Grande Voie des Vignes, 92295 Chatenay-Malabry, France; INRIA saclay Ile-de-France, EPI Digiplant, Parc Orsay Université, 91893 Orsay cedex, France E-mail: phc@nn.fr
• Reffye, INRIA saclay Ile-de-France, EPI Digiplant, Parc Orsay Université, 91893 Orsay cedex, France; CIRAD, UMR AMAP, Montpellier, F-34000 France E-mail: pdr@nn.fr
• Fourcaud, CIRAD, UMR AMAP, Montpellier, F-34000 France E-mail: tf@nn.fr

• Liu, Chengdu Institute of Biology, Chinese Academy of Sciences, P.O. Box 416, Chengdu 610041, P. R. China; Sichuan Academy of Forestry, Chengdu 610081, P. R. China E-mail: xl@nn.cn
• Xu, Chengdu Institute of Biology, Chinese Academy of Sciences, P.O.Box 416, Chengdu 610041, P. R. China E-mail: hx@nn.cn
• Berninger, Département des sciences biologiques, Cp 8888 succ centre ville, Université du Québec à Montréal, Montréal (QC) H3C 3P8, Canada E-mail: fb@nn.ca
• Luukkanen, Viikki Tropical Resources Institute, P.O. Box 28, FI-00014 University of Helsinki, Finland E-mail: ol@nn.fi
• Li, Chengdu Institute of Biology, Chinese Academy of Sciences, P.O.Box 416, Chengdu 610041, P. R. China; Viikki Tropical Resources Institute, P.O. Box 28, FI-00014 University of Helsinki, Finland E-mail: licy@cib.ac.cn

• Vanninen, University of Helsinki, Department of Forest Ecology; mailing address: SAIMA – Centre for Environmental Sciences, Linnankatu 11, FIN-57130 Savonlinna, Finland E-mail: petteri.vanninen@helsinki.fi

• Uri, Institute of Silviculture, Estonian Agricultural University, Kreutzwaldi 5, 51014 Tartu, Estonia E-mail: vuri@eau.ee
• Tullus, Institute of Silviculture, Estonian Agricultural University, Kreutzwaldi 5, 51014 Tartu, Estonia E-mail: ht@nn.ee
• Lõhmus, Institute of Geography, University of Tartu, Vanemuise 46, 51014 Tartu, Estonia E-mail: kl@nn.ee

• Buckley, Environmental Biology Group, Research School of Biological Sciences, The Australian National University, GPO Box 475, Canberra City, ACT 2601, Australia and Cooperative Research Centre for Greenhouse Accounting, RSBS, ANU E-mail: tom_buckley@alumni.jmu.edu
• Miller, Environmental Biology Group, Research School of Biological Sciences, The Australian National University, GPO Box 475, Canberra City, ACT 2601, Australia E-mail: jmm@nn.au
• Farquhar, Environmental Biology Group, Research School of Biological Sciences, The Australian National University, GPO Box 475, Canberra City, ACT 2601, Australia and Cooperative Research Centre for Greenhouse Accounting, RSBS, ANU E-mail: gdf@nn.au

• Koskela, Department of Forest Ecology/Tropical Silviculture Unit, P.O. Box 28, FIN-00014 University of Helsinki, Finland E-mail: jarkko.koskela@helsinki.fi

• Wang, Department of Natural Resources and Environmental Sciences, University of Illinois, Urbana, IL, USA E-mail: wang12@staff2.cso.uiuc.edu
• Poso, Department of Forest Resource Management, P.O. Box 24, FIN-00014 University of Helsinki, Finland E-mail: sp@nn.fi
• Waite, Department of Forest Resource Management, P.O. Box 24, FIN-00014 University of Helsinki, Finland E-mail: mlw@nn.fi
• Holopainen, Department of Forest Resource Management, P.O. Box 24, FIN-00014 University of Helsinki, Finland E-mail: mh@nn.fi