Articles containing the keyword 'distribution'

This study examined the relationships between forest management planning units and patches formed by forest habitat components. The test area used was a part of Koli National Park in North Karelia, eastern Finland. Forest management planning units (i.e. forest compartments) were defined by using a traditional method of Finnish forestry which applies aerial photographs and compartment-wise field inventory. Patches of forest habitat components were divided according to subjective rules by using a chosen set of variables depicting the edaphic features and vegetation of a forest habitat. The spatial distribution of the habitat components was estimated with the kriging-interpolation based on systematically located sample plots. The comparisons of the two patch mosaics were made by using the standard tools of GIS. The results of the study show that forest compartment division does not correlate very strongly with the forest habitat pattern. On average, the mean patch size of the forest habitat components is greater and the number of these patches lower compared to forest compartment division. However, if the forest habitat component distribution had been considered, the number of the forest compartments would have at least doubled after intersection.

• Uuttera, E-mail: ju@mm.unknown
• Hyppänen, E-mail: hh@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

Distribution and occurrence of bark beetles and other forest insects in relation to environmental variation were analysed by multivariate methods. Eight different forest edges were studied using 10 x 10 m sample plots that formed 200 m linear transects perpendicular to the forest edge. Forest edge affected the distribution of insect species only in the edges between mature, non-managed spruce stands and clear cuts or young seedling stands, but not in the pine stands. The occurrence of the selected forest insects mainly depended on variables associated with the amount and quality of suitable woody material. The most significant environmental variables were forest site type, crown canopy coverage, tree species, number of stumps, number of dead spruce trunks and amount of logging waste at site. Quantitative classification of species and sample plots showed that some specialized species (Xylechinus pilosus, Cryphalus saltuarius, Polygraphus poligraphus and P. subopacus) adapted to mature spruce forests, tended to withdraw from the forest edge to interior stand sites. By contrast many generalized species (Pityogenes chalcographus, P. quadridens, Pissodes spp., Hylurgops palliatus, Tomicus piniperda, Dryocoetes spp. and Trypodendron lineatum) benefitted from cuttings and spread over stand borders into mature forest.

• Peltonen, E-mail: mp@mm.unknown
• Heliövaara, E-mail: kh@mm.unknown
• Väisänen, E-mail: rv@mm.unknown

The purpose of this study was to compare the Weibull distributions estimated for the entire growing stock of a stand and separately for Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst.) in describing the basal area diameter distributions in mixed stands. The material for this study was obtained by measuring 553 stands located in eastern Finland. The parameters of the Weibull distribution were estimated using the method of maximum likelihood. The models for these parameters were derived using regression analysis. Also, some parameter models from previous studies were compared with the measured distribution. The obtained distributions were compared using the diameter sums of the entire growing stock, diameter sums by tree species and of the sawtimber part of the growing stock. The results showed that far more accurate results were obtained when the distributions were formed using parameter models separately for the different tree species than when using parameter models for the entire growing stock. This was already true when considering the entire growing stock of the stand and especially when the results were examined by tree species. When the models for the entire growing stock were applied by tree species in relation to basal areas, the results obtained were overestimates for Norway spruce and underestimates for Scots pine. The models from earlier studies, where parameter models were estimated separately for tree species from the National Forest Inventory data, showed good fits also in regard to the data of this study.

• Maltamo, E-mail: mm@mm.unknown

For biomass forestry in the inland parts of Southern and Central Finland, the obvious choice of willow species is Salix myrsinifolia. However, selection of clones of indigenous species has not yet been completed and more research and selection is needed. In the Piipsanneva old peatland trial, indigenous species of willow, mostly clones of S. myrsinifolia and S. phylicifolia, were compared in terms of biomass production, coppicing, height growth and diameter distributions. In this trial, the mean annual biomass production was not particularly high; more important results were attained in the ranking of clones. The trial strengthens the hypothesis that, over the long-term, the biomass production of S. myrsinifolia is higher than that of S. phylicifolia. It was supposed that behind the highest yield there was a clone with uniform quality, one whose diameter distribution would be narrow and positively skewed. Comparisons of parameters of Weibull functions showed that the distributions of the best clones were wide, indicating that those clones use the whole growth space better than those with narrow distribution.

• Honkanen, E-mail: ah@mm.unknown

Yield of Cupressus lusitanica Mill. was modelled by predicting the diameter distribution of trees at given stand ages. The beta distribution was used as a theoretical distribution. The models used for the calculation of diameter distribution were based on 66 temporal sample plots with varying age, site and stand density. The growing sites of Cupressus lusitanica were divided into four classes on the basis of age and dominant height. Using the stand models developed in the study, the yield and profitability of different thinning schedules was evaluated by a simulation technique. In the simulated treatment regimes, the mean annual increment varied from 6.6 m³/ha in the poorest site class to 16.6 m³/ha in the best class with rotation lengths ranging from 25 years (best sites) to 34 years (poorest sites). With typical planting densities (1,600 trees/ha), thinnings increase the total harvest by a few percentage points and improved the profitability of plantation forestry.
The PDF includes an abstract in Finnish.

• Pohjonen, E-mail: vp@mm.unknown
• Pukkala, E-mail: tp@mm.unknown

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
• Kolström, E-mail: tk@mm.unknown

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
• Mubita, E-mail: om@mm.unknown
• Saramäki, E-mail: js@mm.unknown

The paper continues an earlier study by Kilkki and Päivinen concerning the use of the Weibull function in modelling the diameter distribution. The data consists of spruces (Picea abies (L.) H. Karst.) measured on angle count sample points of the National Forest Inventory of Finland. First, maximum likelihood estimation method was used to derive the Weibull parameters. Then, regression models to predict the values of these parameters with stand characteristics were calculated. Several methods to describe the Weibull function by a tree sample were tested. It is more efficient to sample the trees at equal frequency intervals than at equal diameter intervals. It also pays to take separate samples for pulpwood and saw timber.

The PDF includes an abstract in Finnish.

• Kilkki, E-mail: pk@mm.unknown
• Maltamo, E-mail: mm@mm.unknown
• Mykkänen, E-mail: rm@mm.unknown
• Päivinen, E-mail: rp@mm.unknown

The condition of forest road pavements was studied in spring, one week after maintenance and in autumn. The effect of vibrating blade was slightly better than that of pulled drag. Large loose stones couldn’t be pressed into pavement with either of the implements. The use of the vibrating blade was three times as expensive as the use of the pulled drag, however, the blade is suitable for other purposes as well.

The PDF includes an abstract in Finnish.

• Rummukainen, E-mail: ar@mm.unknown

The single tree growth models presented in this study were based on about 4,000 trees measured in 50 even-aged Scots pine (Pinus sylvestris L.) sample plots with varying density, spatial pattern of trees and stand age. Predictors that used information about tree locations decreased the relative standard error of estimate by 10 percentage points (15%), if past growth was not used as a predictor, and about 15 percentage points (30%) when past growth was one of the predictors. When ranked according to the degree of determination, the best growth models were obtained for the basal area increment, the next best for relative growth, and the poorest for diameter increment. The past growth decreased the relative standard error of estimate by 15–20 percentage points, but did not make the spatial predictors unnecessary. The degree of determination of the spatial basal area growth model was almost 80% if the past growth was unknown and almost 90% if the past growth was known. Variables that described the amount of removed competition did not improve the growth models.

The PDF includes an abstract in Finnish.

• Pukkala, E-mail: tp@mm.unknown

The study presents two methods of predicting tree dimensions in a Scots pine (Pinus sylvestris L.) stand if only the location of trees is known. The first method predicts the tree diameter from the spatial location of neighbours. In the second method the diameter distribution of a subarea is estimated from the local stand density. This distribution is then sampled to obtain diameters. In both methods the tree height is predicted with a spatial model on the basis of diameters and locations of trees. The main purpose of the presented models is to generate realistic stands for simulation studies.

The PDF includes an abstract in Finnish.

• Pukkala, E-mail: tp@mm.unknown

The effect of drainage on structure of tree stands is analysed by comparing the average structural characteristics (e.g. diameter distribution) of stands in the data for different drainage age classes and selected site types. The material consists of ca. 4,400 relascope sample plots, which are part of a large drainage area inventory project. The uneven-aged structure of the virgin peatland forest is preserved for several decades after drainage. This is enhanced by the post-drainage increase of small-diameter trees, especially birch. The number of trees per hectare increased during a period of ca. 30 years and levelled off thereafter. The increase in the number of saw log stems is clearly related to the fertility of the site and its geographical location.

The PDF includes a summary in English.

• Hökkä, E-mail: hh@mm.unknown
• Laine, E-mail: jl@mm.unknown

The effect of grouping on 5-year old volume increment was studied by a simulation technique using spatial growth models estimated in Scots pine (Pinus sylvestris L.) stands in the phase of the first commercial thinning. A total of 24 model stands were regenerated by applying 12 spatial processes for two different diameter distributions. In addition to model stands, 6 different thinnings were simulated in two real stands. The clustering of trees was described with Fisher’s grouping index and by estimating the relative interception of diffuse radiation. In model stands with constant diameter distribution the correlation between the grouping index and volume increment ranged from -0.81 to -0.91. The correlation between volume increment and interception was 0.81–0.83 with one diameter distribution and 0.70 if both distributions were combined. In one thinned stand the correlation between the growth estimate and grouping index varied between -0.33 and 0.76. The correlation between interception and growth was about 0.30 in one stand and 0.72 if both stands were combined. Small irregularities do not decrease the volume production of a young Scots pine stand, but if the clustering is considerable or there are reasonably wide harvest strips, growth will be reduced by 10–20%.

The PDF includes a summary in Finnish.

• Pukkala, E-mail: tp@mm.unknown

The paper demonstrates the possibility of using data from small relascope sample plots in the derivation of the regression models which predict the Weibull function parameters for the dbh-distribution. The Weibull parameters describing the basal area dbh-distribution were estimated for relascope sample plots from the Finnish National Forest Inventory. In the first stage of the estimation nonlinear regression analysis was employed to derive initial parameter estimates for the second stage, in which the maximum likelihood method was used. The parameter estimates were employed as dependent variables for the derivation of the regression models; the independent variables comprised of the compartment-wise stand variables generally estimated in ocular inventories.

The PDF includes an abstract in Finnish.

• Kilkki, E-mail: pk@mm.unknown
• Päivinen, E-mail: rp@mm.unknown

Thinning models are generally based on the density of the stand measured by the average basal area per hectare, for instance. These models are handicapped by the uneven structure of the stands. In uneven stands the averages are inadequate indicators for the need and amount of thinnings.

Small relascope plots were tested in the measurement of the spatial distribution of trees and in the determination of the need and amount of thinnings. The thinning quantity was determined as the difference between the actual distribution of the relascope plots into basal area classes and the ideal distribution after thinning. Sequential sampling was used in the derivation of the decision equations. A respective BASIC-program for a programmable pocket calculator is given.

The PDF includes a summary in English.

• Kilkki, E-mail: pk@mm.unknown
• Pohjola, E-mail: tp@mm.unknown
• Pohtila, E-mail: ep@mm.unknown

The study deals with the distribution of above-ground biomass of Vaccinium myrtillus L. along the vegetation continuum segregated by using phytosociological classification method composite clustering. The qualitative characteristics of forest sites corresponding to different vegetational clusters were defined on the basis of indirect gradient analysis of vegetation data and description of tree stand properties in stands in 160 sample areas in Southern Finland.

Six vegetation types differing from each other mainly in abundance of the most constant and dominant plant species were formed. Sample areas with rich grass-herb vegetation, as well as sample areas representing comparatively dry, barren site type were clearly separated from other groups of sample areas. Stand characteristics, particularly the proportional distribution of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst.) seems to be another important factor affecting the vegetation composition.

The lowest biomass values of blueberry were connected with herb-rich vegetation and shady spruce-dominated stands. Comparatively low values were connected to also other spruce-dominated sample areas. Pine-dominant or mixed pine-spruce stands the biomass values were significantly higher. Even if the site quality is essentially equal, the abundance relationships between Vaccinium myrtillus and other components of the ground vegetation may vary in wide ranges and cause difficulties in practical site classification.

The PDF includes a summary in English.

• Kuusipalo, E-mail: jk@mm.unknown

Climatological factors determining the natural northern boundary in Europe of oak (Quercus robur L.) were investigated. The natural northern boundary of oak corresponds in detail to the curve at which the growing season, beginning at +5°C in spring and ending at +10°C in autumn, is of a certain constant length. The northern boundaries for more oceanic plants can be explained by prolonged autumn activity. This is obviously the general explanation or the concept of oceanity. Oak spread markedly in Finland in the summers during 1961–1975, which on an average were as warm but much dried than those during 1931–1960. The importance of humidity for oak was discussed.

The PDF includes a summary in English.

• Solantie, E-mail: rs@mm.unknown

The particle size distribution affects several properties of the soil, thus, the ability to define the texture type of the soil as accurately as possible in field conditions is essential. The soil particle size classification devised by Atterberg (1912) is used in Finnish forestry. The study is based on a small laboratory material. The correlation between some characteristics of the soil particle size distribution, field capacity and cation exchange capacity were determined.

The particle size characteristics such as the relative proportion of different particle sizes, average particle size (Md) and parameters depicting the degree of sorting were determined. The relative proportion of soil particles below 0.06 mm correlated best with both field capacity and cation exchange capacity. Similarly, the average particle size and the degree of sorting correlated well with the field capacity and the cation exchange capacity.

The use of sorting characteristics is not well-suited to the type of soil sample material containing a high proportion of particles of varying size as was used in this material. Such characteristics are probably more easily applicable to the fine sand and sand sediments which are predominant in Finnish forest soils. The most useful particle size distribution characteristics in soils having a great variation in particle sizes were the average particle size and the relative proportion of silt and clay. Thus, the nutrient and water status of the soil can be predicted to some extent by examining the percentage of silt and clay, average particle size and the degree of sorting.

The PDF includes a summary in English.

• Sepponen, E-mail: ps@mm.unknown

Ips acuminatus Gyll. (Coleoptera, Scolytidae) is a bark beetle that causes deep bluing in thin-barked Scots pine (Pinus sylvestris L.) pulpwood. It has been shown that this decreases pulp yield. The purpose of this study was to map the southern border of the distribution of Ips acuminatus in Finland. It was found that there have been changes in the distribution of this species during the last three decades. Ips acuminatus has now disappeared from southern Finland. On the basis of the sample plots (134 cutting areas) the southern border of this pest lies on the line running through the towns Vaasa–Seinäjoki–Äänekoski–Jyväskylä–Pieksämäki–Savonlinna–Punkaharju. A certain degree of localisation was observed in the occurrence of I. acuminatus in its distribution area, for instance, differences in its occurrence frequency in cutting areas and even in log and cutting residue piles in the sample cutting area.

It is considered that the most important reasons for these changes in distribution are the increase in logging and changes in the location of cutting sites, and resulting competition for breeding material for the increased population of bark beetles. Furthermore, the long-distance transport of unpeeled logs from the north across the present southern borders may, in the future, contribute to local changes in the southern distribution of Ips acuminatus.

The PDF includes a summary in English.

• Puukko, E-mail: kp@mm.unknown

The technique of double normalizing, i.e. normalizing the relative needle biomass and the length of the living crown system, is applied to the modelling of the distribution of needle biomass in the canopy of young Scots pine (Pinus sylvestris L.) stands. The study based on the parameters of β-function shows that at the individual-tree level, the variance in needle distribution was not closely associated with any tree characteristics. A shift in the point of maximum needle biomass upwards unsuppressed trees was, however, evident. This was associated with an increase in the height of the trees. At the stand level, the stand mean height and stand density had an equal and a rather high potential for explaining the variance in the needle distribution. The normalized crowns are utilized in models for determining light extinction in the crown. A special technique for determining the amount of photosynthates available for growth in a particular tree is presented.

The PDF includes a summary in Finnish.

• Kellomäki, E-mail: sk@mm.unknown
• Hari, E-mail: ph@mm.unknown
• Ilonen, E-mail: pi@mm.unknown
• Kanninen, E-mail: mk@mm.unknown

The maps concerning the natural distribution of oak (Quercus robur L.) have proved most unreliable in detailed examination. In this paper, the author has collected his observations on natural oak in the westernmost parts of the province of Uusimaa and the easternmost parts of province of Turunmaa, the islands included. Furthermore, the paper includes some viewpoints which must be considered as criteria when determining the naturality of the stand in question. Future borders of oak’s distribution range must be moved farther up north to replace the earlier views of the northern limit of natural oak in Finland.

The PDF includes a summary in English.

• Rainio, E-mail: rr@mm.unknown

The paper describes the systematics, distribution, abundance and nest sites of Formica rufa -group in different Finnish forest types. In addition, it has been estimated the availability of Finnish ants in the biological competition.

F. polyctena, F. aquilonia and F. lugubris are distributed over whole Finland. F. rufa and F. nigricans to Southern Finland only. The relative abundace of ant nests diminish to Northern Finland. F. rufa -group prefer most forest on moist land (Myrtillus and Oxalis-Myrtillus types), mixed forests of Norway spruce (Picea abies (L.) H. Karsts), Scots pine (Pinus sylvestris L.) and birch (Betula sp.), and the silvicultural density 0.6–0.7 (good or satisfactory density), but they avoid broadleaved and pure one-tree species forests. For the biological competition the most competitive ant species seem to be F. polyctena and F. aquilonia.

The PDF includes a summary in English.

• Wuorenrinne, E-mail: hw@mm.unknown

Fomes annosus (Fr.) Cke. (now Heterobasidion annosum (s.str.)) has proved highly adaptable to varying conditions. Thus, the fungus is able to alter the pH as well as in alkalic as acid direction according to the original pH-grade. The fungus spreads mainly by basidiospores or by the sterile mycelium, but maybe also by the conidiospores. The fungus has spread through the temperate zone; in the tropical and sub-tropical zone it is found sporadically. There is a mention in the literature of at least 136 species in which it has been found. It is found in hardwoods but is most disastrous in conifers. The economic losses are considered biggest in England, Germany and Scandinavia.

The research has not been able to find a safe way to protect the trees growing on an infected site. The only way to limit the damage seems to be the use of mixed stands. Stump-protection has proved to be a relatively effective way to prevent the spread of the fungus to uninfected sites. The formerly used creosote has been mainly substituted by new chemicals, such as sodium nitrite. They act by altering the stump in a way that is favourable for antagonists to Fomes annosus, such as Trichoderma viride and Penicillium sp., or the recently presented Peniophora gigantea.

Although the fungus is found in many tree species, there is a difference in the relative resistance of different species. Among the conifers, the Abies-species (with exception of Abies grandis, A. alba and A. sachalienensis) are considered comparatively resistant. The species of Larix and Pseudotsuga are more resistant than those of Picea and Pinus.

The PDF includes a summary in English.

• Palmberg, E-mail: cp@mm.unknown

The aim of the study was to update knowledge of natural range of English oak (Quercus robur L.), European ash (Fraxinus exelsior L.), Norway maple (Acer platanoides L.), small-leaved lime (Tilia cordata Miller), wych elm (Ulmus glabra Mill.) and European white elm (Ulmus laevis Pall.) in Finland, and estimate how far north they could be grown as forest trees or as park trees. The study is based on literature and questionnaires sent to cities and towns, District Forestry Boards, districts of Forest Service, Forestry Management Associations and railway stations.

The northern borders in the natural range of the species succeed one another from south to north as follows: English oak, European ash, Norway maple, wych elm, and small-leaved lime. Occurrence of European white elm is sporadic. The English oak forms forests in the southernmost Finland, while the other species grow only as small stands, groups or solitary trees. According to experiences of planted stands or trees, the northern limits of the species succeed one another from south to north as follows: European ash, English oak, Norway maple, European white elm, wych elm and small-leaved lime. All the species are grown in parks fairly generally up to the district of Kuopio-Vaasa (63 °). The northern limits where the species can be grown as park trees reach considerably further north in the western part of the country than in the east.

The article includes a summary in English.

• Ollinmaa, E-mail: po@mm.unknown

Distribution of European white elm (Ulmus laevis Pallas) is on its northernmost border in Pyhäjärvi and Kokemäenjoki area. This survey describes distribution of European white elm in the flooded shores of the central lake of Pyhäjärvi and Kokemäenjoki river water system.

Both Ulmus laevis and U. montana (now U. Glabra Hudson) can be found in the area, but most of the elms qrowing in thea area are U. laevis. U. laevis occurs around the lake in two separate areas, almost entirely in flooded shores of the lake. Regeneration of elm from seeds was limited on a narrow belt on the higher part of the flooded shore. Consequently, U. laevis can be found as zones around the lake, created by the changes in water level of the lake. The trees are judged to be native for the area.

The article includes an abstract in German.

• Saarnijoki, E-mail: ss@mm.unknown

Aspen (Populus tremula L.) is a common tree in Finland, and has been used, for instance, in matchstick industry. However, there has been little studies on its distribution and properties. In this study, 142 sample trees in different forest site types in Valtimo and Onkamo in Eastern Finland were measured in detail in 1935.

According to the results, during the first 10 years aspens height growth is fastest of the Finnish tree species surpassing, for instance, Scots pine (Pinus sylvestris L.) and birch (Betula sp.) . The diameter growth is similar to Scots pine up to the age of 50 years, after which the growth of aspen exceeds Scots pine. Branchless portion of the stem compared to the height of the tree increases until it reaches about 50% of the height of the tree. In poorer sites aspen is prone to decay.

Aspen regenerates easily both by root shoots and seeds. If root shoots are left to grow, the mother tree should be free of decay. In general, seedlings are of better quality. Good quality aspen stands require thinning and a rich forest type. If an old aspen stand has decay, the trees should be ring-barked and the site regenerated with a new tree species.

The article includes an abstract in German.

• Blumenthal, E-mail: bb@mm.unknown

Occurence of buckthorn (Hippophaës rhamnoides L.) in the mainland coast and archipelago of Rauma in the Southwestern Finland was surveyed during 1934-1936. The species is coastal, growing most prominent in the islands of central zone of the archipelago, while it is rare in the outermost archipelago and loses competition to other vegetation in mainland. The main competitors in the innermost islands are black alder (Alnus glutinosa (L.) Gaertn.) and Norway spruce (Picea abies (L.) H. Karst.) and in the outermost islands black alder and common juniper (Juniperus communis L.). Seawater and ice can cause damage to buckthorn, but it resists wind well. The species grows well both on fine and coarse gravel.

The article includes an abstract in German.

• Enkola, E-mail: ke@mm.unknown

Finland possesses climatic and botanical conditions that can make it rich in game. Several species, for instance blue hare (Lepus timidus L.), squirrel (Sciurus vulgaris L.), red fox (Vulpes vulpes L.) and ermin (Mustela erminea L.), and several migrating bird species are distributed in almost in every parts of the country. Hunting is still unorganized, but restrictive regulations have been established, and the central organization of hunting clubs (Suomen Yleinen Metsästäjäliitto) has member clubs in different part of the country. There is about 70-80,000 hunters in the country. Hunting has influenced the abundance of many species. For instance, European beaver (Castor fiber L.) has been hunted to extinction, and lynx (Lynx lynx L.), wolf (Canis lupus L.), otter (Lutra lutra L.), bear (Ursus arctos L.) and wolverine (Gulo gulo L.) are threatened. Also the distribution of elk (Alces alces L.) is patchy due to hunting.

The article shows distribution and abundance of forest birds, and describes the six game zones in Finland. The game zones correspond the vegetation zones, and have distinctive differences in distribution of the game species. Hunting has previously been important livelihood in Finland, but has this role only in the north in Lapland, Kainuu and Perä-Pohjola, and near the eastern border of the country. The number of hunted small game in the hunting season 1933-1934 are presented by the species. The monetary value of the game is estimated at about 30-40 million Finnish marks annually.

The PDF includes a summary in Finnish.

• Klemola, E-mail: vk@mm.unknown

One of the difficulties in constructing growth and yield tables has been to determine which of the sample plots growing the same tree species and belonging to the same forest site type, with reference to the quality of stands, have to be included in the same growth series.

New growth and yield tables for the most important tree species were constructed in Finland in 1916–1919, using new principles that aim at avoiding some of the common weaknesses. There were two main differences to the earlier work. First, the site quality class (forest site type) was determined for each sample plot when the sample plot was measured, independently of the stand occupying the site. In this way it was possible to treat the sample plots of each site as an independent group from the beginning, and so that the quality classes were the same for all the tree species. Second, mathematic-statistical methods were used to deduct the so-called stem frequency distribution series, when studying which of the sample plots of the same quality class belong to the same growth series. They represent the average number of stems of the different diameter classes. A more detailed description of the method used to create the growth and yield tables is published in Acta Forestalia Fennica no. 15.

In the PDF is included a summary in Finnish.

• Ilvessalo, E-mail: yi@mm.unknown

In an earlier paper of the author it was established that bracken fern (Pteridium aquilinum (L.) Kuhn.) that the sporal regeneration of the species is almost entirely connected with fire, and that the size of the bracken fern clones, distinguished by their characteristics, was related to the time of the fire. The time of the fire was determined by the samples taken with auger from the trees on the sample plots. A large data on the occurrence of bracken fern was collected around Finland, but only part of it could be used in the previous study, as the trees of the site provided no means to find out it the site had been burned earlier.

In earlier studies, a mass occurrence of sporelings of bracken fern in England has been connected to cities bombed and burned during the World War II. In this study the data of the clones is connected to historical sources and the time of wars in Finland. The comparisons in this study have confirmed the results achieved by comparing the dimensions of the bracken clones to the fire dates. It was found that the wars have caused an increase in the regeneration frequency of bracken fern.

• Oinonen, E-mail: eo@mm.unknown

The objective of the present study was to obtain information on the regeneration by spores of bracken fern (Pteridium aquilinum (L.) Kuhn.) as well as the permanence and vegetative spreading of the clones. Prevention of bracken fern, which can hinder forest regeneration, is possible only when the basic facts of the life cycle is known. It would be useful to know if it is probable that bracken fern can become prevalent by spore regeneration, and to what extent it invades forest land by vegetative spreading.

No bracken fern sporelings were found, and the experiments of regeneration by spores were unsuccessful, therefore, the studies were concentrated on the clones. Due to the fire tolerance of the plant, it was expected that the clone material would show gradation according to the periods of fire. The first part of the work concerns individual variation in bracken, the second part concentrates on the data collected from sample plots, which latest fire could be dated from the trees.

The results of the studied clones confirm the correlation between the stands interpreted as clones and the length of the post-fire period. The stands were delimited to clones by their individual characteristics. The spreading on average sites (Vaccinium and Myrtillus type forests) was in average 35.8±2 cm annually. It is concluded that bracken fern regeneration by spores is very rare in Finland and that it has been rarer during the last 50 years compared to the preceding period. This is probably caused by the end of slash-and-burn cultivation and decrease of forest fires in Finland. Bracken fern clones often survive the fires through their rhizomes, and fragments of old clones originating before the fire could be found in the study areas. These clones may be even 300 years old. Especially in its northern areas of distribution, bracken fern is connected with settlement and old slash and burn sites. Regeneration by spores in the northern distribution areas seem to be less than in the southern areas.

• Oinonen, E-mail: eo@mm.unknown

There has not been complete agreement as to what is meant by ectendotrophic mycorrhizae, and there is a wide variety of opinion among authors on mycorrhizal terminology. In this paper ectendotrophic mycorrhizae are defined to be short roots with Hartig net and intracellular hyphae in the cortex. A mantle and digestion of intracellular hyphae may be found but are not necessary. In the study of Mikola (1965) ectendotrophic mycorrhiza was found to be common in Scots pine (Pinus sylvestris L.) seedlings in Finnish nurseries. The mycorrhizae had always similar structure and the mycelium isolated from the seedlings (E-strains) was similar. The aim of this study was to find out what kind of ectendotrophic mycorrhizae exist in forests and nurseries outside Finland, what kind of mycorrhizae do the E-strains isolated from Scots pine form with other tree species, and are these associations symbiotic.

Only one type of ectendotrophic mycorrhiza was found on the 600 short roots collected from the continents of Europa and America. The type was similar to the one described by Mikola: the mycelium is coarse and forms a strong Hartig net, and intracellular infection is heavy. Evidence is convincing that this structure was formed by the same fungus species. The species is unidentified. Mycorrhizae synthesized by E-strain with six spruce species, fir, hemloch and Douglas fir were all ectotrophic.

The E-type ectendotrophic mycorrhizae proved to be a balanced symbiosis. The seedlings of 13 tree species inoculated with the E-strain grew in the experiment better than the controls. The observation that ectendotrophic mycorrhizae dominates in the nurseries but is seldom found in forests, and then only in seedlings growing in the forest, was confirmed in the study. In synthesis experiments E-strain formed either ecto- or ectendotrophic mycorrhiza depending on the tree species.

• Laiho, E-mail: ol@mm.unknown

Norway spruce (Picea abies (L.) H. Karst.) is a species that becomes in Finland over time the dominant species in the sites that are suitable for it. The reason that it covers only a quarter of the forest areas in Finland depends mainly on forest fires. The aim of this review was to discuss the biological factors that affect competition between Scots pine and Norway spruce.

Especially important is the ability to regenerate and grow past seedling stage. There does not seem to be significant differences in the number of good seed and seedling years of the species. Spruce regenerates better on moss covered forest floor than pine. On the other hand, pine seedlings grow faster than spruce seedlings, and tolerate better dry conditions. Consequently, one of the defining biological differences is that Norway spruce needs more humid conditions than Scots pine. Spruce is shown to have greater transpiration than pine. Spruce also has higher site requirements, however, growing as undergrowth, it seems to be better able to compete of the nutrients with the larger trees than pine. It also tolerates shading better. Spruce is less frost tolerant than pine.

The PDF includes a summary in German.

• Aaltonen, E-mail: va@mm.unknown

The article discusses the thermal conditions in the northern limits of trees and some bushes in Finland. Temperature is the most important limiting factor for distribution of plant species. Precipitation variations, however, are small in Finland. The article lists the main features of thermal conditions during the different seasons in different parts of Finland. The northern limits and the thermal condition of the area are described for the following species: Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst.), mezereon, buckthorn, common alder, linden, elm, maple, hazel, ash, oak, hybrid mountain ash, yew and Swedish whitebeam.

The PDF includes a summary in English.

• Keränen, E-mail: jk@mm.unknown

The paper presents preliminary results of paleobotanical studies on vegetation in Åland, south-west Finland. The investigations concentrated on studying arrival of tree species and stratigraphy of peatlands. According to the studies, some plant fossils found in the peat (Ceratophyllum submersum, Sparagnium neglectum, Najas flexilis) indicate that climate of the region has earlier been warmer than at the present. The present forests in Åland are dominated by coniferous species, but the pollen analysis of the peat indicate that Norway spruce (Picea abies (L.) H. Karst.) became a common species in the region about by the time of Christ’s birth. The species has reached its present distribution in Åland relatively late. The pollen analyses give relatively little information about the arrival of birch (Betula sp.) and Scots pine (Pinus sylvestris L.), but it seems obvious that occurrence of birch reached its culmination just before spruce. During the warm period common alder (Alnus glutinosa (L.) Gaertn.) was the most important species, and also pollen of oak (Quercus robur L.), kinden (Tilia cordata L.) and elm (Ulmus sp.) was relatively common in the peat of some of the studied peatlands. An interesting finding was the pollen of Carpinus betulus in many sites in Åland.

The PDF includes a Finnish and German summary.

• Backman, E-mail: ab@mm.unknown

The article describes the distribution of the European white elm; its sites and vegetation communes; phenotype (size and form); variations in the leaves; inflorescence and fruiting; germinative capacity of the seeds; regeneration, both vegetative propagation and from seeds; commercial use of the timber; and the history of European white elm.

The PDF contains a summary in Finnish.  

• Linkola, E-mail: kl@mm.unknown

The northern range of small leaved lime (Tilia cordata Mill.) in Finland has remained the same since the end of 1800s, but according to the studies of subfossiles of lime found in peatlands, the northern limit has once been higher than at the present. The northernmost natural specimens of the species in Reisjärvi do not produce seed, and are therefore probably a relict. The article includes a review on the distribution of the species in Finland and its capacity to regenerate. The natural regeneration of lime in Finland is at present very rare. The species has lost its ability to sexual reproduction, but reproduces readily vegetatively.

The PDF includes a summary in German.

• Hertz, E-mail: mh@mm.unknown

The first proper growth and yield tables were prepared in Finland already in 1872, but they have been used little as the needs of forestry and forest sciences increased. One of the problems of the old yield tables was how the site quality classes are determined. The new growth and yield tables use the forest site type classification, which enables the use of same site types for all tree species. This makes it possible to compare the growth of different tree species in same kind of sites. The tables also use stem frequency distribution series. In the first stage, the tables were prepared for Southern and Central Finland.

The PDF includes a summary in German.

• Ilvessalo, E-mail: yi@mm.unknown

A strip survey was made to define the forest and peatland site class distribution and the condition of the forests in Savo and Karelia in central and eastern parts of Finland. According to the survey, 24% of the forested lands are peatlands. Fresh mineral soil sites (26%) were the most common mineral soil site type. Intermediately dry forest soil sites covered 22% of the area, forest sites with grass-herb vegetation 12,79%, rich grass-herb forest soil sites 3,16% and dry forest soil sites 9,59% of the forested area. The most common tree species were Scots pine (Pinus sylvestris L.), 39%, Betula sp., 26%, Norway spruce (Picea abies (L.) H. Karst.), 18%, and grey alder (Alnus incana (L.) Moench), 10% of the forest land. The article includes a review about the wood harvesting in the forests, and their present silvicultural state. According to the study, about 30% of the forested lands (not including peatlands) were unproductive; mostly mixed alder and birch stands of poor quality or open lands.

The PDF includes a summary in German.

• Multamäki, E-mail: sm@mm.unknown

The data has been collected from northern Finland between about 64th and 68^th north latitudes, excluding the polar tree line areas. The sample plots have been selected to represents greatest variation of the habitats in altitude, rainfall and other site factors. The selected trees were cut, their age, height, and diameter at various heights examined and possible signs of forest fires noticed. The age of the trees was examined also with microscope. The age class distribution of the sample plots was studied. The determination of historical seed years was based on age class distribution of the sample plots.  

Grouping of the trees into different age classes was too weak a method to make any conclusions about the periodicity or even less about the frequency of the seed years.  There were also noticeable differences in determining the age of the trees between macroscopic and microscopic age examination. There are also differences in the amount of seedlings between different forest types.

• Lakari, E-mail: ol@mm.unknown

The article is a review on shifting cultivation, its methods and use in Finland, and its effect on the condition of forests. Shifting cultivation decreases forest reserves not only by burning large amounts of wood. Of the area used for shifting cultivation, 10-50% can be open land. The older age classes of forests are often missing, and range of tree species shift towards deciduous trees. This causes lack of large timber. The shorter the rotation, the less well the most valuable trees survive on the area. One reason is lack of seed trees. Of the coniferous trees, Scots pine (Pinus sylvestris L.) is able to survive in the burnt-over lands better than Norway spruce (Picea abies (L.) H. Karst.), because it can produce seeds at a relatively young age. Betula sp. and especially grey alder (Alnus incana (L.) Moench) regenerate well on burnt-over lands. Also the frequency of good seed years determine which tree species become the dominant species on a burnt-over site.

When shifting cultivation is abandoned, deciduous trees keep their advantage over coniferous trees, because the wood of coniferous trees is used more in the surrounding villages. Pine and spruce spread to the burnt-over areas from the poorer sites that often had remained unburned. In densely populated areas in some counties in Savo in eastern Finland, where shifting cultivation was practiced intensively, Norway spruce became rare. Dominant tree species in the burnt-over areas became birch and pine.

• Heikinheimo, E-mail: oh@mm.unknown

To enhance the utilization of the wood, the sawmills are forced to place more emphasis on planning to master the whole production chain from the forest to the end product. One significant obstacle to integrating the forest-sawmill-market production chain is the lack of appropriate information about forest stands. Since the wood procurement point of view in forest planning systems has been almost totally disregarded there has been a great need to develop an easy and efficient pre-harvest measurement method, allowing separate measurement of stands prior to harvesting. The main purpose of this study was to develop a measurement method for Scots pine (Pinus sylvestris L.) stands which forest managers could use in describing the properties of the standing trees for sawing production planning.

Study materials were collected from ten Scots pine stands located in North Häme and South Pohjanmaa, in Southern Finland. The data comprise test sawing data on 314 pine stems, diameter at breast height (dbh) and height measures of all trees and measures of the quality parameters of pine sawlog stems in all ten study stands as well as the locations of all trees in six stands. The study was divided into four sub-studies which deal with pine quality prediction, construction of diameter and dead branch height distributions, sampling designs and applying height and crown height models. The final proposal for the pre-harvest measurement method is a synthesis of the individual sub-studies.

Quality analysis resulted in choosing dbh, distance from stump height to the first dead branch, crown height and tree height as the most appropriate quality characteristics of Scots pine. Dbh and dead branch height are measured from each pine sample tree while height and crown height are derived from dbh measures by aid of mixed height and crown height models. Pine and spruce diameter distribution as well as dead branch height distribution are most effectively predicted by the kernel function. Roughly 25 sample trees seem to be appropriate in pure pine stands. In mixed stands the number of sample trees needs to be increased in proportion to the intensity of pines in order to attain the same level of accuracy.

• Uusitalo, E-mail: ju@mm.unknown

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

An extensive field-based survey was conducted to establish the distribution of site types on drained peatlands, the condition of the drainage networks, the post-drainage development of the tree stands, their structure and silvicultural condition and the corresponding requirements for operational measures. The data is based on sampling of the forest drainage undertaking during 1930–78 and consists of 1,312 km inventory transect, 6,030 relascope sample plots and 21,700 studied ditches.

Of the studied peatlands more than 60% were Scots pine (Pinus sylvestris L.) mires, slightly under 20% Norway spruce (Picea abies) mires, and under 10% each treeless mires and paludified upland forest sites. The remaining peatland area that is to be considered suitable for forest drainage according to criteria used by Heikurainen (1960) now consists mainly of spruce mires and paludified upland forest types; about 1 million ha both groups still remain undrained.

The proportion of ditches in need of ditch cleaning was estimated to be under 10% in the youngest drained areas and under 30% in the oldest. The mean tree stand volumes of the drained peatlands of different site types show the same dependence on the trophic level as in earlier studies but the volumes seem to be some 5–10% lower. These results compare favourably with those of the 7th national forest inventory.

Trends in the post-drainage development of tree stand volumes and increment are also, generally, in accordance with earlier findings but have somewhat lower values. The development of the nutrient-poor site type stands, especially in Northern Finland, seems to be significantly poorer than was earlier assumed.

The PDF includes a summary in English.

• Keltikangas, E-mail: mk@mm.unknown
• Laine, E-mail: jl@mm.unknown
• Puttonen, E-mail: pp@mm.unknown
• Seppälä, E-mail: ks@mm.unknown

Fungal diaspores were caught in Southern Finland (Helsinki, Turku, Jyväskylä, Lappeenranta) and in Northern Finland (Oulu, Ivalo) in 1967—68 on exposed discs of Picea abies (L.) Karst. wood. In the laboratory, the diaspores on the discs developed mycelia which stained the wood. A month after exposure fungi and bacteria were isolated from stained areas.

The number of identified fungal species was relatively high and included fungi of different taxonomic groups. The most common fungi identified were Peniophora gigantea and Trichoderma viride. The most common Agaricaceae obtained were species of Hypholoma. Of the fungi imperfecti, relatively high numbers of not only Trichoderma viride but also of the Alternaria and Fusarium species were isolated. According to the investigation, species of several fungal groups seem to participate in the early stages of the decayed process of spruce.

The PDF includes a summary in Finnish.

• Kallio, E-mail: tk@mm.unknown

• Halme, VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT Espoo, Finland https://orcid.org/0000-0002-7517-6663 E-mail: eelis.halme@vtt.fi
• Mõttus, VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT Espoo, Finland https://orcid.org/0000-0002-2745-1966 E-mail: matti.mottus@vtt.fi

The natural northern distribution limit for pedunculate oak (Quercus robur L.) is in southern Finland. We hypothesized that the maximum frost hardiness (FH_max) in the winter limited the cultivation of oaks in northern latitudes. We tested the hypothesis with controlled freezing tests in midwinter. The acorns for the experiment were collected from the four main oak populations in southernmost Finland. The seedlings were raised in the nursery, frost hardened in field conditions, and then moved to a growth chamber at –2 °C on two occasions in winter and tested for FH_max in controlled freezing tests. Frost hardiness was assessed by differential thermal analysis (DTA) based on the low temperature exotherm (LTE) and relative electrolyte leakage (REL) of the stem, and visual damage scoring (VD) of the buds and stem. The initiation and peak of the LTE took place at an average of –41 °C and –43 °C respectively, without differences among the populations. The variation in the initiation and peak of the LTE was high, ranging from –34.6 °C to –45.5 °C and from –37.1 °C to –46.9 °C respectively. According to the REL method, the frost hardiness of the populations ranged from –44.0 °C to –46.4 °C in February and from –40.6 °C to –41.6 °C in March, without significant differences among the populations. According to VD, the bud was the least frost hardy organ, with FH between –19 °C and –33 °C, depending on population and assessment time. We conclude that the maximum hardiness may set the limit for the distribution of pedunculate oak northwards, but the high within-population variation offers potential to breed more frost hardy genotypes.

• Repo, Natural Resources Institute Finland (Luke), Natural Resources, Yliopistokatu 6b, FI-80100 Joensuu, Finland https://orcid.org/0000-0002-7443-6275 E-mail: tapani.repo@luke.fi
• Volanen, Kalevankatu 4b B21, FI-80110 Joensuu, Finland E-mail: virva.volanen@siunsote.fi
• Pulkkinen, Natural Resources Institute Finland (Luke), Production systems, Latokartanonkaari 9, FI-00790 Helsinki, Finland https://orcid.org/0000-0002-1643-7691 E-mail: pertti.pulkkinen@luke.fi

Studies of the spatial patterns of dominant plant species may provide significant insights into processes and mechanisms that maintain stand stability. This study was performed in a permanent 1 ha plot in evergreen and deciduous broad-leaved mixed forests on Tianmu Mountain. Based on two surveys (1996 and 2012), the dynamics of the spatial distribution pattern of the dominant population (Cyclobalanopsis myrsinifolia (Blume) Oersted) and the intra- and interspecific relationships between C. myrsinifolia and other dominant species populations were analyzed using Ripley’s K(r) function. We identified the importance value of a species in a community, which is the sum of the relative density, relative frequency, and relative dominance. The drivers of spatial distribution variation and the maintenance mechanisms of the forest were discussed. The results showed that the importance value of C. myrsinifolia within the community decreased over the past 16 years. The C. myrsinifolia population exhibited a significantly aggregated distribution within a spatial scale of 0–25 m in 1996 whereas it changed to a random distribution at scales larger than 5.5 m in 2012. From 1996 to 2012, the spatial distribution patterns between C. myrsinifolia and Cyclocarya paliurus (Batal.) Iljinsk. and between C. myrsinifolia and Cunninghamia lanceolata (Lamb.) Hook did not change significantly. In 1996, C. myrsinifolia and Daphniphyllum macropodum Miq. were positively associated at the scale of 0–25 m; this relationship was strongly significant at the scale of 6–10 m. However, there was no association between the populations of two species in terms of the spatial distribution at the scale of 0–25 m in 2012. Our findings indicate that the drivers of variation in the spatial distribution of the C. myrsinifolia population were intra- and interspecific mutual relationships as well the seed-spreading mechanism of this species.

• Yang, Zhejiang Forest Resources Monitoring Center, Hangzhou 310020, China E-mail: 20080095@zafu.edu.cn
• Yi, School of Forestry and Biotechnology, Zhejiang A & F University, Lin’an 311300, China E-mail: yilita@zafu.edu.cn
• Ye, School of Forestry and Biotechnology, Zhejiang A & F University, Lin’an 311300, China E-mail: 542243187@qq.com
• Wu, School of Forestry and Biotechnology, Zhejiang A & F University, Lin’an 311300, China E-mail: 326585523@qq.com
• Liu, School of Forestry and Biotechnology, Zhejiang A & F University, Lin’an 311300, China E-mail: mhliu@zafu.edu.cn

Hybrid aspen (Populus tremula L. × P. tremuloides Michx.) is known with outstanding growth rate and some favourable wood characteristics, but models for stand management have not yet been prepared in northern Europe. This study introduces methods and models to predict tree dimensions, diameter at breast height (dbh) and tree height for a hybrid aspen plantation using data from repeatedly measured permanent sample plots established in clonal plantations in southern Finland. Dbh distributions using parameter recovery method for the Weibull function was used with Näslund’s height curve to model tree heights. According to the goodness-of-fit statistics of Kolmogorov-Smirnov and the Error Index, the arithmetic mean diameter (D) and basal area-weighted mean diameter (DG) provided more stable parameter recovery for the Weibull distribution than the median diameter (DM) and basal area-weighted median diameter (DGM), while DG showed the best overall fit. Thus, Näslund’s height curve was modelled using DG with Lorey’s height (HG), age, basal area (BA), and tree dbh (Model 1). Also, Model 2 was tested using all predictors of Model 1 with the number of trees per ha (TPH). All predictors were shown to be significant in both Models, showing slightly different behaviour. Model 1 was sensitive to the mean characteristics, DG and HG, while Model 2 was sensitive to stand density, including both BA and TPH as predictors. Model 1 was considered more reasonable to apply based on our results. Consequently, the parameter recovery method using DG and Näslund’s models were applicable for predicting tree diameter and height.

• Lee, Natural Resources Institute Finland (Luke), Natural resources, Latokartanonkaari 9, FI-00790 Helsinki, Finland https://orcid.org/0000-0003-1586-9385 E-mail: daesung.lee@luke.fi
• Siipilehto, Natural Resources Institute Finland (Luke), Natural resources, Latokartanonkaari 9, FI-00790 Helsinki, Finland E-mail: jouni.siipilehto@luke.fi
• Hynynen, Natural Resources Institute Finland (Luke), Natural resources, Vipusenkuja 5, FI-57200 Savonlinna, Finland https://orcid.org/0000-0002-9132-8612 E-mail: jari.hynynen@luke.fi

Dalbergia latifolia Roxb., commonly known as rosewood, is one of the highly valuable tropical timber species of Nepal. The tree species was widely distributed in the past, however, over-exploitation of natural habitat, deforestation, forest conversion for agriculture, illegal logging and the invasion of alien species resulted in the classification of this species as vulnerable by the IUCN (International Union for Conservation of Nature) category. So, the prediction of habitat suitability and potential distribution of the species is required to develop restoration mechanisms and conservation interventions. In this study, we modelled the suitable habitat of D. latifolia over the entire possible range of Nepal using a Maxent model. We compiled 23 environmental variables (19 bioclimatic, 3 topographic and a vegetative layer), however, only 12 least correlated variables along with 43 spatially representative presence locations were retained for model prediction. We used a receiver operating characteristic (ROC) curve to assess the model’s performance and a Jackknife procedure to evaluate the relative importance of predictor variables. The model was statistically significant with an area under the curve (AUC) value of 0.969. The internal Jackknife test indicated that elevation was the most important variable for the model prediction with 71.3% contribution followed by mean temperature of driest quarter (9.8%). The most (>0.6) suitable habitat for the D. latifolia was 235 484 hectares with large sections of area in two provinces whereas, the western most provinces were not suitable for D. latifolia as per Maxent model. The information presented here can provide a framework for nature conservation planning, monitoring and habitat management of this rare and endangered species.

• Mahatara, Forest Research and Training Centre, Government of Nepal, P.O. Box 3339, Babarmahal, Kathmandu 44600, Nepal E-mail: honeystar73@gmail.com
• Acharya, Forest Research and Training Centre, Government of Nepal, P.O. Box 3339, Babarmahal, Kathmandu 44600, Nepal E-mail: acharya.amulkumar@gmail.com
• Dhakal, Forest Research and Training Centre, Government of Nepal, P.O. Box 3339, Babarmahal, Kathmandu 44600, Nepal E-mail: dhakalbp.shorea@gmail.com
• Sharma, Forest Research and Training Centre, Government of Nepal, P.O. Box 3339, Babarmahal, Kathmandu 44600, Nepal E-mail: dipeshsharmadiyu2015@gmail.com
• Ulak, Forest Research and Training Centre, Government of Nepal, P.O. Box 3339, Babarmahal, Kathmandu 44600, Nepal E-mail: sunitaulak@gmail.com
• Paudel, Agriculture Forestry University, P.O. Box 13712 Rampur, Chitwan, Nepal E-mail: prashant.paudel88@gmail.com

In remote sensing-based forest inventories 3D point cloud data, such as acquired from airborne laser scanning, are well suited for estimating the volume of growing stock and stand height, but tree species recognition often requires additional optical imagery. A combination of 3D data and optical imagery can be acquired based on aerial imaging only, by using stereo photogrammetric 3D canopy modeling. The use of aerial imagery is well suited for large-area forest inventories, due to low costs, good area coverage and temporally rapid cycle of data acquisition. Stereo-photogrammetric canopy modeling can also be applied to previously acquired imagery, such as for aerial ortho-mosaic production, assuming that the imagery has sufficient stereo overlap. In this study we compared two stereo-photogrammetric canopy models combined with contemporary satellite imagery in forest inventory. One canopy model was based on standard archived imagery acquired primarily for ortho-mosaic production, and another was based on aerial imagery whose acquisition parameters were better oriented for stereo-photogrammetric canopy modeling, including higher imaging resolution and greater stereo-coverage. Aerial and satellite data were tested in the estimation of growing stock volume, volumes of main tree species, basal area and diameter and height. Despite the better quality of the latter canopy model, the difference of the accuracy of the forest estimates based on the two different data sets was relatively small for most variables (differences in RMSEs were 0–20%, depending on variable). However, the estimates based on stereo-photogrammetrically oriented aerial data retained better the original variation of the forest variables present in the study area.

• Tuominen, Natural Resources Institute Finland (Luke), Bioeconomy and Environment, P.O. Box 2, FI-00791 Helsinki, Finland E-mail: sakari.tuominen@luke.fi
• Balazs, Natural Resources Institute Finland (Luke), Bioeconomy and Environment, P.O. Box 2, FI-00791 Helsinki, Finland E-mail: andras.balazs@luke.fi
• Kangas, Natural Resources Institute Finland (Luke), Bioeconomy and Environment, P.O. Box 68, FI-80101 Joensuu, Finland E-mail: annika.kangas@luke.fi

We modelled the effect of habitat composition and roads on the number and occurrence of moose (Alces alces L.) damage in Ostrobothnia and Lapland using a zero-inflated count model. Models were developed for 1 km², 25 km² and 100 km² landscapes consisting of equilateral rectangular grid cells. Count models predict the number of damage, i.e. the number of plantations and zero models the probability of a landscape being without damage for a given habitat composition. The number of moose damage in neighboring grid cells was a significant predictor in all models. The proportion of mature forest was the most frequent significant variable, and an increasing admixture of mature forests among plantations increased the number and occurrence of damage. The amount of all types of plantations was the second most common significant variable predicting increasing damage along with increasing amount of plantations. An increase in thinning forests as an admixture also increased damage in 1 km² landscapes in both areas, whereas an increase in pine-dominated thinning forests in Lapland reduced the number of damage in 25 km² landscapes. An increasing amount of inhabited areas in Ostrobothnia and the length of connecting roads in Lapland reduced the number of damage in 1 and 25 km² landscapes. Differences in model variables between areas suggest that models of moose damage risk should be adjusted according to characteristics that are specific to the study area.

• Nikula, Natural Resources Institute Finland (Luke), Bioeconomy and Environment, Ounasjoentie 6, FI-96200 Rovaniemi, Finland E-mail: ari.nikula@luke.fi
• Nivala, Natural Resources Institute Finland (Luke), Bioeconomy and Environment, Ounasjoentie 6, FI-96200 Rovaniemi, Finland E-mail: vesa.nivala@luke.fi
• Matala, Natural Resources Institute Finland (Luke), Natural resources, Yliopistokatu 6, FI-80100 Joensuu, Finland E-mail: juho.matala@luke.fi
• Heliövaara, University of Helsinki, Department of Forest Sciences, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: kari.heliovaara@helsinki.fi

Optical 2D remote sensing techniques such as aerial photographing and satellite imaging have been used in forest inventory for a long time. During the last 15 years, airborne laser scanning (ALS) has been adopted in many countries for the estimation of forest attributes at stand and sub-stand levels. Compared to optical remote sensing data sources, ALS data are particularly well-suited for the estimation of forest attributes related to the physical dimensions of trees due to its 3D information. Similar to ALS, it is possible to derive a 3D forest canopy model based on aerial imagery using digital aerial photogrammetry. In this study, we compared the accuracy and spatial characteristics of 2D satellite and aerial imagery as well as 3D ALS and photogrammetric remote sensing data in the estimation of forest inventory variables using k-NN imputation and 2469 National Forest Inventory (NFI) sample plots in a study area covering approximately 5800 km². Both 2D data were very close to each other in terms of accuracy, as were both the 3D materials. On the other hand, the difference between the 2D and 3D materials was very clear. The 3D data produce a map where the hotspots of volume, for instance, are much clearer than with 2D remote sensing imagery. The spatial correlation in the map produced with 2D data shows a lower short-range correlation, but the correlations approach the same level after 200 meters. The difference may be of importance, for instance, when analyzing the efficiency of different sampling designs and when estimating harvesting potential.

• Tuominen, Natural Resources Institute Finland (Luke), Economics and Society, P.O. Box 2, FI-00791 Helsinki, Finland E-mail: sakari.tuominen@luke.fi
• Pitkänen, Natural Resources Institute Finland (Luke), Economics and Society, P.O. Box 2, FI-00791 Helsinki, Finland E-mail: timo.p.pitkanen@luke.fi
• Balazs, Natural Resources Institute Finland (Luke), Economics and Society, P.O. Box 2, FI-00791 Helsinki, Finland E-mail: andras.balazs@luke.fi
• Kangas, Natural Resources Institute Finland (Luke), Economics and Society, P.O. Box 68, FI-80101 Joensuu, Finland E-mail: Annika.Kangas@luke.fi

An understanding of the genetic variation of the beech, especially at the edge of its natural distribution, is essential because of the change in natural distribution of the species resulting from changing climatic conditions. The main aim of the study was to determine the level of genetic diversity of European beech at the north-eastern edge of its natural range. The other aim was to check the genetic variation of beech from the two centres, the north and the south of Poland, which were identified in previous findings based on pollen analyses and phenotypic traits. The research material was the progeny of twelve beech provenances. The genetic structure of the populations was determined by ten highly variable microsatellite DNA loci. The results confirmed the high genetic diversity of beech at the north-eastern edge of its natural distribution, which infers the probability of their good adaptation to the changing climate and an extension of the range. Genetic analyses confirmed the existence of two genetic centres for beech in Poland. The populations from south-eastern Poland had a slightly higher diversity than the populations from the north-western area, which may indicate that the colonisation of Poland occurred by two routes. The results are important for creating the borders of the provenance regions and for limiting the transfer of seeds and seedlings. The choice of forest reproductive material, based on the knowledge of genetic diversity, is very important for the stability of future forests.

• Kempf, Department of Genetics and Forest Tree Breeding, Faculty of Forestry, University of Agriculture in Krakow, Al. 29-listopada 46, 31–425 Krakow E-mail: m.kempf@ur.krakow.pl
• Konnert, Bavarian Office for Forest Seeding and Planting, Forstamtsplatz 1, 83317 Teisendorf, Germany E-mail: monika.konnert@asp.bayern.de

Accurate timber assortment information is required before cuttings to optimize wood allocation and logging activities. Timber assortments can be derived from diameter-height distribution that is most often predicted from the stand characteristics provided by forest inventory. The aim of this study was to assess and compare the accuracy of three different pre-harvest inventory methods in predicting the structure of mainly Scots pine-dominated, clear-cut stands. The investigated methods were an area-based approach (ABA) based on airborne laser scanning data, the smartphone-based forest inventory Trestima app and the more conventional pre-harvest inventory method called EMO. The estimates of diameter-height distributions based on each method were compared to accurate tree taper data measured and registered by the harvester’s measurement systems during the final cut. According to our results, grid-level ABA and Trestima were generally the most accurate methods for predicting diameter-height distribution. ABA provides predictions for systematic 16 m × 16 m grids from which stand-wise characteristics are aggregated. In order to enable multimodal stand-wise distributions, distributions must be predicted for each grid cell and then aggregated for the stand level, instead of predicting a distribution from the aggregated stand-level characteristics. Trestima required a sufficient sample for reliable results. EMO provided accurate results for the dominating Scots pine but, it could not capture minor admixtures. ABA seemed rather trustworthy in predicting stand characteristics and diameter distribution of standing trees prior to harvesting. Therefore, if up-to-date ABA information is available, only limited benefits can be obtained from stand-specific inventory using Trestima or EMO in mature pine or spruce-dominated forests.

• Siipilehto, Natural Research Institute Finland (Luke), Management and Production of Renewable Resources, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: jouni.siipilehto@luke.fi
• Lindeman,  Natural Research Institute Finland, Green Technology, Kaironiementie 15, 39700 Parkano E-mail: harri.lindeman@luke.fi
• Vastaranta, University of Helsinki, Department of Forest Sciences, P.O. Box 62 (Viikinkaari 11), FI-00014 University of Helsinki E-mail: mikko.vastaranta@helsinki.fi
• Yu, Finnish Geospatial Research Institute (FGI), Department of Remote Sensing and Photogrammetry, National Land Survey of Finland, P.O. Box 15 (Geodeetinrinne 2), FI-02431, Masala, Finland E-mail: xiaowei.yu@maanmittauslaitos.fi
• Uusitalo,  Natural Research Institute Finland, Green Technology, Kaironiementie 15, 39700 Parkano E-mail: jori.uusitalo@luke.fi

• Fahlvik, 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
• Ekö, Southern Swedish Forest Research Centre, Swedish University of Agricultural Sciences, P.O. Box 49, SE-230 53 Alnarp, Sweden E-mail: per.magnus.eko@slu.se
• Petersson, StoraEnso Skog AB, Åsgatan 22, SE-791 80 Falun, Sweden E-mail: nils.petersson@storaenso.com

• Siipilehto, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: jouni.siipilehto@metla.fi
• Mehtätalo, University of Eastern Finland, School of Computing, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: lauri.mehtatalo@uef.fi

• Zasada, Warsaw University of Life Sciences, Faculty of Forestry, Laboratory of Dendrometry and Forest Productivity, Nowoursynowska 159, 02-776 Warsaw, Poland E-mail: michal.zasada@wl.sggw.pl

• Siipilehto, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: jouni.siipilehto@metla.fi

• Havimo, University of Helsinki, Department of Forest Resource Management, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: mikko.havimo@helsinki.fi
• Rikala, University of Helsinki, Department of Forest Resource Management, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: jr@nn.fi
• Sirviö, University of Helsinki, Department of Forest Resource Management, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: js@nn.fi
• Sipi, University of Helsinki, Department of Forest Resource Management, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: ms@nn.fi

• Peuhkurinen, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: jp@nn.fi
• Maltamo, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: mm@nn.fi
• Malinen, Finnish Forest Research Institute, Joensuu Research Unit, P.O. Box 68, FI-80101 Joensuu, Finland E-mail: jm@nn.fi

• Koskela, University of Tampere, Dept of Mathematics, Statistics and Philosophy, FI-33014 University of Tampere, Finland E-mail: laura.koskela@uta.fi
• Sinha, Indian Statistical Institute, Kolkata, India E-mail: bks@nn.in
• Nummi, University of Tampere, Dept of Mathematics, Statistics and Philosophy, FI-33014 University of Tampere, Finland E-mail: tn@nn.fi

• Nurminen, University of Joensuu, Faculty of Forest Sciences; Forest Agency Tuomo Nurminen, Joensuuntie 5 B 8, FI-41800 Korpilahti, Finland E-mail: tn@nn.fi
• Heinonen, Finnish Forest Research Institute, Joensuu Research Unit, P.O. Box 68, FI-80101 Joensuu, Finland E-mail: jh@nn.fi

• Kangas, Department of Forest Resources Management, P.O.Box 27, FI-00014 University of Helsinki, Finland E-mail: ak@nn.fi
• Mehtätalo, University of Joensuu, Faculty of Forestry, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: lm@nn.fi
• Maltamo, University of Joensuu, Faculty of Forestry, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: mm@nn.fi

• Siipilehto, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: jouni.siipilehto@metla.fi
• Sarkkola, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: ss@nn.fi
• Mehtätalo, University of Joensuu, Faculty of Forestry, P.O. Box 111, 80101 Joensuu, Finland E-mail: lm@nn.fi

• Tanskanen, Department of Forest Ecology, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: niina.tanskanen@helsinki.fi
• Ilvesniemi, Finnish Forest Research Institute, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: hi@nn.fi

• Uusitalo, The Finnish Forest Research Institute, Parkano unit, FI-39700 Parkano, Finland E-mail: jori.uusitalo@metla.fi
• Puustelli, University of Tampere, Department of Mathematics, Statistics and Philosophy, FI-33014 University of Tampere, Finland E-mail: ap@nn.fi
• Kivinen, University of Helsinki, Department of Forest Resource Management, Box 27, FI-00014 University of Helsinki, Finland E-mail: vpk@nn.fi
• Nummi, University of Tampere, Department of Mathematics, Statistics and Philosophy, FI-33014 University of Tampere, Finland E-mail: tn@nn.fi
• Sinha, Stat-Math Division, Indian Statistical Institute, 203 B.T. Road, Kolkata - 700 108, India E-mail: bks@nn.in

• Siipilehto, Finnish Forest Research Institute, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: jouni.siipilehto@metla.fi

• Siipilehto, Finnish Forest Research Institute, Vantaa Research Centre, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: jouni.siipilehto@metla.fi
• Siitonen, Finnish Forest Research Institute, Vantaa Research Centre, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: juha.siitonen@metla.fi

• Sterba, BOKU – University of Natural Resources an Applied Life Sciences, Vienna, Peter Jordanstrasse 82, A-1190 Vienna, Austria E-mail: hubert.sterba@boku.ac.at

• Sarkkola, University of Helsinki, Department of Forest Ecology, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: sakari.sarkkola@helsinki.fi
• Hökkä, Finnish Forest Research Institute, Rovaniemi Research Station, P.O. Box 16, FI-96301 Rovaniemi, Finland E-mail: hh@nn.fi
• Penttilä, Finnish Forest Research Institute, Vantaa Research Centre, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: tp@nn.fi

• 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

• Peltola, University of Joensuu, Faculty of Forestry, P.O. Box 111, FIN-80101 Joensuu, Finland E-mail: heli.peltola@forest.joensuu.fi
• Miina, Finnish Forest Research Institute, Joensuu Research Centre, P.O. Box 68, FIN-80101 Joensuu, Finland E-mail: jm@nn.fi
• Rouvinen, University of Joensuu, Faculty of Forestry, P.O. Box 111, FIN-80101 Joensuu, Finland E-mail: ir@nn.fi
• Kellomäki, University of Joensuu, Faculty of Forestry, P.O. Box 111, FIN-80101 Joensuu, Finland E-mail: sk@nn.fi

• Kangas, University of Helsinki, Dept. of Forest Resources Management, P.O. Box 27, 00014 University of Helsinki, Finland E-mail: annika.kangas@helsinki.fi
• Maltamo, University of Joensuu, Faculty of Forestry, P.O. Box 111, 80101 Joensuu, Finland E-mail: mm@nn.fi

• Kokkila, University of Helsinki, Department of Forest Ecology, P.O. Box 27, FIN-00014 Helsingin yliopisto, Finland E-mail: tero.kokkila@helsinki.fi
• Mäkelä, University of Helsinki, Department of Forest Ecology, P.O. Box 27, FIN-00014 Helsingin yliopisto, Finland E-mail: am@nn.fi
• Nikinmaa, University of Helsinki, Department of Forest Ecology, P.O. Box 27, FIN-00014 Helsingin yliopisto, Finland E-mail: en@nn.fi

• Zucchini, Georg-August-Universität Göttingen, Institute for Statistics and Econometrics E-mail: zucchini@wi-wiss.uni-goettingen.de
• Schmidt, Forest Research Station of Lower Saxony E-mail: ms@nn.de
• Gadow, Georg-August-Universität Göttingen, Institute for Forest Management and Yield Sciences E-mail: kvg@nn.de

• Kangas, Finnish Forest Research Institute, Kannus Research Station, P.O. Box 44, FIN-69101 Kannus, Finland E-mail: annika.kangas@metla.fi
• Maltamo, Finnish Forest Research Institute, Joensuu Research Station, P.O. Box 68, FIN-80101 Joensuu, Finland E-mail: mm@nn.fi

• Kangas, Finnish Forest Research Institute, Kannus Research Station, P.O. Box 44, FIN-69101 Kannus, Finland E-mail: annika.kangas@metla.fi
• Maltamo, Finnish Forest Research Institute, Joensuu Research Station, P.O. Box 68, FIN-80101 Joensuu, Finland E-mail: mm@nn.fi

• Siipilehto, Finnish Forest Research Institute, Vantaa Research Centre, P.O. Box 18, FIN-01301 Vantaa, Finland E-mail: jouni.siipilehto@metla.fi

• Siipilehto, Finnish Forest Research Institute, Vantaa Research Centre, P.O. Box 18, FIN-01301 Vantaa, Finland E-mail: jouni.siipilehto@metla.fi

• Krooks, Finnish Geodetic Institute, Geodeetinrinne 2, FI–02431 Masala, Finland E-mail: Anssi.Krooks@fgi.fi
• Kaasalainen, Finnish Geodetic Institute, Geodeetinrinne 2, FI–02431 Masala, Finland E-mail: Sanna.Kaasalainen@fgi.fi
• Kankare, Department of Forest Sciences, University of Helsinki, P.O. Box 27, FI-00014 Helsinki, Finland E-mail: ville.kankare@helsinki.fi
• Joensuu, Department of Forest Sciences, University of Helsinki, P.O. Box 27, FI-00014 Helsinki, Finland E-mail: marianna.joensuu@alumni.helsinki.fi
• Raumonen, Tampere University of Technology, Department of Mathematics, P.O. Box 553, Tampere, FI-33101, Finland E-mail: Pasi.Raumonen@tut.fi
• Kaasalainen, Tampere University of Technology, Department of Mathematics, P.O. Box 553, Tampere, FI-33101, Finland E-mail: Mikko.Kaasalainen@tut.fi

• Tahvanainen, Finnish Forest Research Institute, P.O. Box 68, FI-80101 Joensuu, Finland E-mail: timo.tahvanainen@metla.fi
• Kaartinen, University of Joensuu, Faculty of Forestry, P.O. Box 111, FI-80101 Joensuun yliopisto, Finland E-mail: kk@nn.fi
• Pukkala, University of Joensuu, Faculty of Forestry, P.O. Box 111, FI-80101 Joensuun yliopisto, Finland E-mail: tp@nn.fi
• Maltamo, University of Joensuu, Faculty of Forestry, P.O. Box 111, FI-80101 Joensuun yliopisto, Finland E-mail: mm@nn.fi