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Articles containing the keyword 'effect'

Category : Article

article id 5613, category Article
Mikko Peltonen, Kari Heliövaara, Rauno Väisänen. (1997). Forest insects and environmental variation in stand edges. Silva Fennica vol. 31 no. 2 article id 5613. https://doi.org/10.14214/sf.a8514
Keywords: forest management; bark beetles; biodiversity; distribution; edge effect; forest ecology; occurrence
Abstract | View details | Full text in PDF | Author Info

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 (email)
  • Heliövaara, E-mail: kh@mm.unknown
  • Väisänen, E-mail: rv@mm.unknown
article id 5561, category Article
Jari Liski. (1995). Variation in soil organic carbon and thickness of soil horizons within a boreal forest stand – effect of trees and implications for sampling. Silva Fennica vol. 29 no. 4 article id 5561. https://doi.org/10.14214/sf.a9212
Keywords: Pinus sylvestris; soil carbon; spatial variation; soil formation; soil morphology; tree effects; soil sampling; geostatics
Abstract | View details | Full text in PDF | Author Info

Spatial variation in the density of soil organic carbon (kg/m2) and the thickness of soil horizons (F/H, E) were investigated in a 6 m x 8 m area in Scots pine (Pinus sylvestris L.) stand in Southern Finland for designing an effective sampling for the C density and studying the effect of trees on the variation. The horizon thickness of the podzolized soil were measured on a total of 126 soil cores (50 cm deep) and the C density of the organic F/H and 0–10 cm, 10–20 cm and 20–40 cm mineral soil layers was analysed.

The C density varied 3–5 fold within the layers and the coefficients of variation ranged from 22 % to 40%. Considering the gain in confidence per sample, 8–10 samples were suggested for estimating the mean C density in the F/H and 0–40 cm layers, although about 30 samples are needed for 10% confidence in the mean. The C densities and horizon thicknesses were spatially dependent within the distances of 1–8 m, the spatial dependence accounting for 43–86% of the total variance. The F/H layer was thicker and contained more C within 1–3 m radius from trees. In the 10–20 cm and 20–40 cm layers (B horizon) the C density also increased towards the trees, but more pronouncedly in the immediate vicinity of the stems. Because the spatial patterning of the E horizon thickness was similar, the increase was attributed to stemflow and precipitation of organic compounds in the podzol B horizon.

  • Liski, E-mail: jl@mm.unknown (email)
article id 5534, category Article
Hyun Kang, Inger Ekberg, Gösta Eriksson, Johan Ununger. (1994). Second and third growth period responses of Picea abies families to first growth period photoperiodic, light intensity and temperature treatments. Silva Fennica vol. 28 no. 4 article id 5534. https://doi.org/10.14214/sf.a9174
Keywords: Picea abies; growth; maturation; temperature; seedlings; photoperiod; environmental effects; genetic effects; juvenility
Abstract | View details | Full text in PDF | Author Info

Seedlings of Picea abies (L.) H. Karst. full-sib families of contrasting origins were cultivated in a phytotron under different photoperiodic, light-intensity and temperature treatments during their first growth period. The effects of the treatments on juvenile growth traits – whether enhanced or delayed maturation was induces – were observed during the two subsequent growth periods. The following hypotheses were tested: (A) Enhanced maturation can be induced in the first growth period from sowing with (i) a long period of continuous light during active growth (24 weeks vs. 8 weeks); (ii) a shorter night during bud maturation (12 h vs. 16 h); high temperature (25°C vs. 20°C) during (iii) active growth, growth cessation and bud maturation; and during (iv) the latter part of growth cessation and bud maturation only. (B) Delayed maturation can be induced after (i) low light intensity during growth cessation and bud maturation (114 μmol m-2 s-1 vs. 340 μmol m-2 s-1); low temperature (15°C vs. 20°C) during (ii) active growth, growth cessation and bud maturation; and during (iii) the latter part of growth cessation and bud maturation only.

The most dramatic effect was observed after 24 weeks of continuous light during active growth. All traits showed a significantly more mature performance in the second growth period compared with the control. The effect for all but one trait was carried over to the third growth period. This is in accordance with the hypothesis that the activity of apical shoot meristems controls the maturation process. For the other treatments there was only weak or no support for the hypothesis of induction of enhanced or delayed maturation. Strong family effects were observed for all traits. Differential responses of the various latitudinal families were observed, suggesting that family effects must be considered to predict and interpret correctly how plants will respond to environmental effects.

  • Kang, E-mail: hk@mm.unknown (email)
  • Ekberg, E-mail: ie@mm.unknown
  • Eriksson, E-mail: ge@mm.unknown
  • Ununger, E-mail: ju@mm.unknown
article id 5515, category Article
Seppo Vehkamäki. (1993). Metsien käytön muutospaineet. Silva Fennica vol. 27 no. 3 article id 5515. https://doi.org/10.14214/sf.a15676
English title: Pressures for changes in the use of forests.
Original keywords: metsänhoito; metsätalous; metsien monikäyttö; kestävyys; tuottavuus; tehokkuus
English keywords: forest management; productivity; sustainability; forestry; multiple use of forests; effectiveness
Abstract | View details | Full text in PDF | Author Info

The paper discusses how the general trend towards increasing growth and productivity in the European societies is expressed also in forestry. It is reflected, for instance, in the increasing production and productivity of forest industries. Technological progress and call for economic growth require great flexibility from all resources. These pressures for effectiveness and production also concern Finnish forestry and forest management. Industrialization, urbanization and development of forestry have increased the pressure to use forests in recreation, preserving human environment and nature conservation in addition to production of timber. Through the development the definition of sustainability has become wider.

  • Vehkamäki, E-mail: sv@mm.unknown (email)
article id 5420, category Article
Toyohiro Miyazava, Jukka Laine. (1990). Effect of macroclimate on the development of Scots pine seedling stands on drained oligotrophic pine mires. Silva Fennica vol. 24 no. 2 article id 5420. https://doi.org/10.14214/sf.a15574
Keywords: Pinus sylvestris; fertilization; regeneration; drained peatlands; plantations; ditch spacing; effective temperature sum; microtopography
Abstract | View details | Full text in PDF | Author Info

The influence of different fertilization treatments and ditch spacings on the height growth of young Scots pine (Pinus sylvestris L.) seedling stands growing under various climatic regimes were determined. Comparisons were made between naturally regenerated and planted seedling stands. The effective temperature sum had a stronger effect on the height growth of planted seedlings, and in Northern Finland the planted seedlings seemed to be influenced to a greater degree by the adverse climatic conditions. The heavier the dose of fertilizer that had been applied, the greater the difference in growth caused by macroclimate. A considerably larger proportion of natural seedlings were located on hummocks compared with that of planted seedlings, irrespective of the region. On plots with wider ditch spacings, seedlings growing on hummocks were superior in height growth to those on flat surfaces.

The PDF includes an abstract in Finnish.

  • Miyazava, E-mail: tm@mm.unknown (email)
  • Laine, E-mail: jl@mm.unknown
article id 5281, category Article
Ilpo Tikkanen. (1986). Search for innovative forest policies and programs. Silva Fennica vol. 20 no. 4 article id 5281. https://doi.org/10.14214/sf.a27718
Keywords: forest policy; effectiveness; policy science; policy analysis
Abstract | View details | Full text in PDF | Author Info

This paper considers the problems of world’s forestry and emphasizes the policy nature of the most threatening issues. A policy science approach is needed in order to be able to provide effective tools to solve the problems. Incremental forest policies followed are evaluated to be too tardy to respond to the many forestry issues of today. Managing the global forestry issues presupposes the design of new and more effective and efficient public policy programs. More profound policy analysis is therefore needed to improve the intellectual basis for planning and decision making. The advancement of the research on the effectiveness presupposes further development of the theories of timber supply and forestry investments as well as the improvement of national forestry statistics. The whole forest policy process should be a subject to intensified systematic research.

  • Tikkanen, E-mail: it@mm.unknown (email)
article id 5183, category Article
Risto Ojansuu, Helena Henttonen. (1983). Kuukauden keskilämpötilan, lämpösumman ja sademäärän paikallisten arvojen johtaminen Ilmatieteen laitoksen mittaustiedoista. Silva Fennica vol. 17 no. 2 article id 5183. https://doi.org/10.14214/sf.a15099
English title: Estimation of the local values of monthly mean temperature, effective temperature sum and precipitation sum from the measurements made by the Finnish Meteorological Office.
Original keywords: sademäärä; lämpösumma; paikallisilmasto; laskentamenetelmä; keskilämpötila; ilmastotekijät; trendipintamenetelmä
English keywords: modelling; effective temperature sum; local climate; monthly mean temperature; precipitation sum; trend surface method; climatic factors
Abstract | View details | Full text in PDF | Author Info

Methods involving the use of moving averages, trend surfaces and their combination are compared in deriving local values of monthly mean temperatures and precipitation sums from the observations made by the Finnish Meteorological Office. Correlation between meteorological variables and sea index, lake index and height above sea level were used in the trend surface method and in the combined method. Combined method, with a trend surface calculated from means of a long time period, was the most reliable method to estimate long local time series.

A method to calculate unbiased estimates of effective temperature sums from monthly mean temperatures is presented.

The PDF includes a summary in English.

  • Ojansuu, E-mail: ro@mm.unknown (email)
  • Henttonen, E-mail: hh@mm.unknown
article id 4908, category Article
Juhani Päivänen. (1974). Sarkaleveyden ja naveroinnin vaikutus pohjavesipinnan syvyyteen ja männyntaimiston kehitykseen lyhytkortisella nevalla. Silva Fennica vol. 8 no. 4 article id 4908. https://doi.org/10.14214/sf.a14752
English title: The effect of ditch spacing and furrowing on depth of ground water table and on development of a Scots pine plantation on small-sedge bog.
Original keywords: mänty; ojitetut suot; avosuot; pituuskasvu; sarkaleveys; naverointi; kuivatussyvyys; kuivatusteho
English keywords: Pinus sylvestris; drained peatlands; Scots pine; height growth; seedlings; open peatlands; drainage effect; ground water table; ditch spacing; furrowing
Abstract | View details | Full text in PDF | Author Info

The paper describes the results obtained from an investigation into the effect of ditch spacing, ditch depth and furrowing on ground water table and on development of a Scots pine (Pinus sylvestris L.) plantation on open small-sedge bog in Central Finland (60° 50’ N; 24° 20’ E), drained in 1967. The area was planted in 1968 with 2+1 Scots pine transplants, and fertilized with Y fertilizer for peat soils. The seedlings were measured in 1972.

The depth of the ground water table was greater, the narrower the ditch spacing. The water furrows shortened the duration of the high ground water and lowered the ground water table particularly in the case of ineffective drainage. The narrower the ditch spacing within the blocks, the higher were the young trees. On the other hand, the differences in the height of the trees between the ditch spacings were eliminated by the effect of the furrows.

The PDF includes a summary in English.

  • Päivänen, E-mail: jp@mm.unknown (email)
article id 4885, category Article
Ilpo Tikkanen. (1973). Metsäpoliittisten toimenpiteiden vaikuttavuus. Silva Fennica vol. 7 no. 3 article id 4885. https://doi.org/10.14214/sf.a14722
English title: Effectiveness of policy measures as applied to small woodlands.
Original keywords: metsäpolitiikka; metsänomistajat; vaikuttavuus; päätöksenteko
English keywords: forest policy; forest owners; effectiveness; decision-making
Abstract | View details | Full text in PDF | Author Info

The paper deals with the methodological problems concerning policy planning and evaluation in small woodlands. A methodological approach to effectiveness of forest policy measures calls, according to the author, for using a frame of reference formed by general economic theory and models of forest owners’ behaviour. Thus, it is important for the selection of forest policy means, and for evaluating the likely effects of a policy, to know the behaviour of the decision makers being influenced. The use of models of forest owners’ behaviour in planning forest policy is motivated by the fact that measures must often affect the woodlot through the owners’ decision making.

The PDF includes a summary in English.

  • Tikkanen, E-mail: it@mm.unknown (email)
article id 4770, category Article
Kustaa Seppälä. (1968). Ennakkotuloksia suometsiköiden ojituksen jälkeisestä kehityksestä ja siihen vaikuttavista tekijöistä. Silva Fennica vol. 2 no. 3 article id 4770. https://doi.org/10.14214/sf.a14555
English title: Preliminary results of post-drainage development of peatland stands in Finland.
Original keywords: kasvu; suometsät; turvekankaat; ojitetut suot; kuivatustehokkuus; ojaväli
English keywords: drained peatlands; increment; draining intensity; ditch interval; drainage effect; stand recovery
Abstract | View details | Full text in PDF | Author Info

The present paper is a preliminary report of a project designed to determine the order of profitability of various forest improvement measures – seeding and planting, drainage, and fertilization – in various types of stands and in different parts of the country on drained peatlands. Sample plot data on the effect of draining on increment was derived from areas drained 28– 36 years ago. The study was carried out in the southern half of Finland.

The observations on increment changes are based on two measurements of the sample stands 12 years apart. Supplementary calculations indicate that the stands on drained peatland, depending on site quality and tree species, have either continued to grow like mineral-soil sites of similar fertility or have somewhat increased their growth rate.

The effect of draining intensity was studied using strip measurements. It was found that both the total amount of wood produced (current stand + cutting removal + natural removal) and the current annual volume increment for the 5-year period systematically decrease as the ditch interval increases. The decrease is, however, relatively slight. In Eriophorum vaginatum pine swamps, the total amount of wood produced and the increment show a decrease of ca. 20% with an increase in ditch interval from 20 to 60 metres. In other sites, the decrease is ca. 5-10%

It can be concluded that if the increase in ditch interval do not result in considerably poorer timber assortment distributions than indicates by stand production and increment, it is profitable to pan for a relatively large ditch interval and a slightly smaller than maximum wood production. Supplementary data and check calculations may cause some changes in these preliminary results.

The PDF includes a summary in English.

  • Seppälä, E-mail: ks@mm.unknown (email)

Category : Article

article id 7144, category Article
Leo Heikurainen, Kustaa Seppälä. (1963). Kuivatuksen tehokkuus ja turpeen lämpötalous. Acta Forestalia Fennica vol. 76 no. 4 article id 7144. https://doi.org/10.14214/aff.7144
English title: The effect of drainage degree on temperature conditions of peat.
Original keywords: turvekankaat; ojitetut suot; kuivatustehokkuus; turpeen lämpötila; lämpötalous
English keywords: drained peatlands; drainage effect; moisture; temperature conditions
Abstract | View details | Full text in PDF | Author Info

The determination of biologically most favourable strip width in peatlands to be drained has been hindered by lack of information of the temperature conditions in the surface peat and in the air close to the ground after drainage of different intensities. Temperature measurements were carried out on peatlands drained to different degrees in Central Finland in the summers of 1960 and 1961. The ground water level in the measuring points, and the strip width served as the criterion for differences in water condition.

When the drainage became more intensive, the temperature of the surface peat decreased. However, temperature differences were small, and discernible only when the differences of water conditions were considerable. The effect of strip condition to temperature seems to be of similar nature than the ground water level. Even in extreme cases temperature differences due to different drainage intensity were relatively small, and seldom exceeded 2°C.

Differences in temperature dependent on the growing stock may be as high as 10°C. Thus, the temperature of the surface peat may be dependent on factors more important than temperature differences caused by aspects of drainage. A well-drained peatland is coldest at the beginning of a growing season compared with poorly drained peatland. The temperature differences increase deeper in the peat. This is caused by the better heat conductivity of the moist peat. Also, daily variations in temperature in the surface peat are large in moist peat.

The PDF includes a summary in English.

  • Heikurainen, E-mail: lh@mm.unknown (email)
  • Seppälä, E-mail: ks@mm.unknown
article id 7643, category Article
Pauline Oker-Blom. (1986). Photosynthetic radiation regime and canopy structure in modeled forest stands. Acta Forestalia Fennica no. 197 article id 7643. https://doi.org/10.14214/aff.7643
Keywords: spatial variation; radiation models; penumbra; grouping effect; photosynthetic radiation
Abstract | View details | Full text in PDF | Author Info

The relationship between canopy structure and photosynthetic radiation regime are studied in a theoretical basis. In modelling the canopy structure, a statistical approach is applied and the radiation field inside a stand is described in terms of random variables and their distribution. A comparison is made between horizontally homogenous stands and grouped forest stands in order to assess the influence of grouping of foliage on the irradiance distribution in a forest stand. Results show that grouping considerably reduces the interception of radiation and causes a large spatial variation. In coniferous stands the grouping of needles into shoots and the effect of penumbra are shown to have an important influence on the distribution of radiation on the needle area.

The PDF includes a summary in Finnish.

  • Oker-Blom, E-mail: po@mm.unknown (email)
article id 7639, category Article
Matti Keltikangas, Jukka Laine, Pasi Puttonen, Kustaa Seppälä. (1986). Vuosina 1930-1978 metsäojitetut suot: ojitusalueiden inventoinnin tuloksia. Acta Forestalia Fennica no. 193 article id 7639. https://doi.org/10.14214/aff.7639
English title: Peatlands drained for forestry during 1930–1978: results from field surveys of drained areas.
Original keywords: suotyypit; ojitetut suot; inventointi; kuivatusteho; ojaverkosto; metsänhoidollinen tila
English keywords: inventory; forest drainage; drainage effect; site type distribution; silvicultural condition; ditch network
Abstract | View details | Full text in PDF | Author Info

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 (email)
  • Laine, E-mail: jl@mm.unknown
  • Puttonen, E-mail: pp@mm.unknown
  • Seppälä, E-mail: ks@mm.unknown
article id 7633, category Article
Helena Henttonen. (1984). The dependence of annual ring indices on some climatic factors. Acta Forestalia Fennica no. 186 article id 7633. https://doi.org/10.14214/aff.7633
Keywords: Pinus sylvestris; Norway spruce; Picea abies; Scots pine; precipitation; temperature; effective temperature sum; annual ring index
Abstract | View details | Full text in PDF | Author Info

The paper concerns relationship between climatic factors and annual ring indices mainly in Southern Finland. The studied index series were from papers of different authors and from different localities. The monthly mean temperatures and precipitation sums were derived from the measurements of meteorological stations. Effective temperature sums for different periods of the year were calculated from the monthly mean temperatures.

The autocorrelation functions were estimated for each index series. The autocorrelations at lag I were significant except for one series. Altogether the differences in the structures of the index series were noticeable, especially between the Scots pine (Pinus sylvestris L.) index series. The influence of climatic factors on the annual ring index variation was studied using cross correlation analysis, simple distributed lag models and transfer function-noise models.

The decisive factor for the annual ring index variation of Norway spruce (Picea abies (L.) H. Karst.) appears to be the effective temperature sum of the growing season. Warm periods during latter parts of previous summer had a negative effect on indices. For the variation of the Scots pine indices the most important climatic factors were the effective temperature sum of the latter part of the growing season and, especially on the arid sites, the precipitation sum during May-July.

The PDF includes a summary in Finnish.

  • Henttonen, E-mail: hh@mm.unknown (email)

Category : Climate resilient and sustainable forest management – Research article

article id 23042, category Climate resilient and sustainable forest management – Research article
Johanna Jääskeläinen, Lauri Korhonen, Mikko Kukkonen, Petteri Packalen, Matti Maltamo. (2024). Individual tree inventory based on uncrewed aerial vehicle data: how to utilise stand-wise field measurements of diameter for calibration? Silva Fennica vol. 58 no. 3 article id 23042. https://doi.org/10.14214/sf.23042
Keywords: laser scanning; calibration; mixed-effects model; single-tree detection
Highlights: A practical scheme to improve the accuracy of predicted tree and stand attributes in an uncrewed aerial vehicle based individual tree inventory; Accuracy was considerably improved with data from 2–4 sample trees from the target stand; Calibrated existing models and the construction of local models performed equally well; The laborious task of constructing a local model can be avoided by using a calibrated transferred model.
Abstract | Full text in HTML | Full text in PDF | Author Info
Uncrewed aerial vehicles (UAV) have great potential for use in forest inventories, but in practice they can be expensive for relatively small inventory areas as a large number of field measurements are needed for model construction. One proposed solution is to transfer previously constructed models to a new inventory area and to calibrate these with a small number of local field measurements. Our objective was to compare calibration of general models and the construction of new models to determine the best approach for UAV-based forest inventories. Our material included field measurements and UAV-based laser scanning data, from which individual trees were automatically identified. A general mixed-effects model for diameter at breast height (DBH) had been formulated earlier based on data from a geographically wider area. It was calibrated to the study area with field measurements from 2–10 randomly selected calibration trees. The calibrated diameters were used to calculate the diameter of a basal area median tree (DGM), tree volumes, and the volume of all trees at plot-level. Next, new DBH-models were formulated based on the 2–10 randomly selected trees and calibrated with plot-level random effects estimated during model construction. Finally, plot-specific height-diameter regression models were formulated by randomly selecting 10 trees from each plot. Calibration reduced the prediction errors of all variables. An increase in the number of calibration trees decreased error rates by 1–6% depending on the variable. Calibrated predictions from the general mixed-effects model were similar to the separately formulated mixed-effects models and plot-specific regression models.

Category : Research article

article id 10544, category Research article
Lars Sprengel, Heinrich Spiecker, Shuirong Wu. (2022). Two subject specific modelling approaches to construct base-age invariant polymorphic site index curves with varying asymptotes. Silva Fennica vol. 56 no. 1 article id 10544. https://doi.org/10.14214/sf.10544
Keywords: generalized algebraic difference approach; stem analysis; dummy variable approach; gnls; nonlinear mixed-effects models; nlme; Zhongtiaoshan forest region
Highlights: Base-age invariant families of height growth curves with polymorphism and varying asymptotes are presented for the seven economically most important tree species in Zhongtiaoshan forest region, China; The nonlinear fixed-effects approach outperforms the nonlinear mixed-effects approach according to the AIC, but according to RMSE and bias these results are not fully supported.
Abstract | Full text in HTML | Full text in PDF | Author Info

For constructing growth and yield models the concept of site index as measure of productivity is crucial. Here, we use nonlinear mixed-effects models (NLME) with random individual effects and nonlinear models with dummy variables as fixed individual effects (NLFE) to fit mechanistic growth functions to stem analysis data of the economically most important tree species in Zhongtiaoshan forest region, China. The Richards and Lundqvist function are formulated into five dynamic equations (R1, R2, L1, L2 and L3) applying the generalized algebraic difference approach (GADA), which inherit polymorphism, varying asymptotes and base-age invariance. According to Akaike information criterion the R1 model as NLFE fits height growth data of Pinus tabuliformis Carrière, Pinus armandii Franch., Quercus liaotungensis Koidz., Quercus aliena Blume and Betula platyphylla Sukaczev best, while for Quercus variabilis Blume R2 as NLFE fits height growth data best. For Larix principis-rupprechtii Mayr L1 as NLME has been selected as best model, as R1 and R2 both as NLFE and NLME are not extrapolating the comparably short length of height growth data well enough. However, according to the root mean square error and bias differences between model fits of both the selected equation and the chosen model fitting approach are not so clear. Presented families of height growth curves serve as planning tools to identify site index and therefore assess productivity of forest stands in the studied region. A direct comparison of the productivity of forest stands of the same tree species is possible due to base-age invariance of the selected models.

  • Sprengel, Chair of Forest Growth and Dendroecology, Albert-Ludwigs-University Freiburg, Tennenbacher Str. 4, 79106 Freiburg, Germany ORCID https://orcid.org/0000-0002-6332-7911 E-mail: lars.sprengel@iww.uni-freiburg.de (email)
  • Spiecker, Chair of Forest Growth and Dendroecology, Albert-Ludwigs-University Freiburg, Tennenbacher Str. 4, 79106 Freiburg, Germany E-mail: instww@uni-freiburg.de
  • Wu, Research Institute of Forest Policy and Information, Chinese Academy of Forestry, No. 1 Dongxiaofu, Haidian District, Beijing 100091, China E-mail: shuirongwu@126.com
article id 10612, category Research article
Daesung Lee, Jouni Siipilehto, Jari Hynynen. (2021). Models for diameter distribution and tree height in hybrid aspen plantations in southern Finland. Silva Fennica vol. 55 no. 5 article id 10612. https://doi.org/10.14214/sf.10612
Keywords: Näslund’s height curve; Weibull distribution; parameter recovery; Populus tremula × P. tremuloides; clonal plantation; nonlinear mixed-effects model
Highlights: Parameter recovery method for the Weibull function fitted diameter distributions well by means of sum and mean forest stand characteristics for hybrid aspen plantations; Arithmetic and weighted mean diameters performed better for the recovery method than the corresponding median diameters; Two alternative Näslund’s height curve models with stand characteristics and tree dbh predictors provided unbiased tree height predictions.
Abstract | Full text in HTML | Full text in PDF | Author Info

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 ORCID https://orcid.org/0000-0003-1586-9385 E-mail: daesung.lee@luke.fi (email)
  • 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 ORCID https://orcid.org/0000-0002-9132-8612 E-mail: jari.hynynen@luke.fi
article id 10507, category Research article
Karri Uotila, Timo Saksa. (2021). Cost-efficient pre-commercial thinning: effects of method and season of early cleaning. Silva Fennica vol. 55 no. 4 article id 10507. https://doi.org/10.14214/sf.10507
Keywords: productivity; young stand management; cost-effectiveness; release treatment
Highlights: The first stage of multistage pre-commercial thinning, early cleaning, took 27–30% less time when carried out in the spring instead of the summer; The two stage pre-commercial thinning program was 11% less expensive to apply when early cleaning had been applied in the spring instead of the summer.
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This study’s aim was to identify how the application season and the method of early cleaning (EC), the first stage of multistage pre-commercial thinning (PCT), affected the time consumption in EC and in the subsequent second PCT operation. The worktime in EC was recorded in the spring, summer, and autumn in 22 sites, which were either totally cleaned or point cleaned. Later, these sites were measured at the time of the second PCT. Time consumption was estimated in PCT, based on the removal of the sites. The time consumption in EC was 5.3 productive work hours (pwh) ha–1, 7.3 pwh ha–1, and 6.2 pwh ha–1 respectively in the spring, summer, and autumn. EC in the spring instead of the summer saved 27–30% of working time, depending on the cleaning method. Point cleaning was 0.8 pwh ha–1 quicker than total cleaning, but the difference was statistically insignificant. The second stage, PCT, was 1 pwh ha–1 slower to conduct in sites which had been early cleaned in the spring instead of the summer. However, at the entire management program level, EC applied in the spring or autumn instead of the summer saved 11% or 5% respectively of the total discounted costs (3% interest rate) of multistage pre-commercial thinning. Today, the commonest time to conduct EC is in the summer, which was the most expensive of the analyzed management alternatives here. We can expect savings in juvenile stand management in forestry throughout boreal conifer forests by rethinking the seasonal workforce allocation.

  • Uotila, Natural Resources Institute Finland (Luke), Natural resources, Juntintie 154, FI-77600 Suonenjoki, Finland E-mail: karri.uotila@luke.fi (email)
  • Saksa, Natural Resources Institute Finland (Luke), Natural resources, Juntintie 154, FI-77600 Suonenjoki, Finland E-mail: timo.saksa@luke.fi
article id 10449, category Research article
Emanuel Strieder, Sonja Vospernik. (2021). Intra-annual diameter growth variation of six common European tree species in pure and mixed stands. Silva Fennica vol. 55 no. 4 article id 10449. https://doi.org/10.14214/sf.10449
Keywords: growing season; climate effects; dendrometer; logistic model; mixing effect; seasonal growth; social tree position
Highlights: 244 intra-annual growth patterns of six tree species on five sites in mixed and corresponding pure stands were analyzed; Humid sites showed a longer growing season than dry sites; Deciduous species showed an earlier growth culmination than conifer species; Mixture effects were both positive and negative and clearly differed between years, indicating that climate alters mixture effects.
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Studies of intra-annual growth are particularly useful for understanding tree growth because of their high temporal resolution. This study was performed in Austria and included hourly band dendrometer data of 244 annual tree recordings from six tree species (Picea abies (L.) Karst., Pinus sylvestris L., Larix decidua Mill., Abies alba Mill., Fagus sylvatica L., Quercus spp. (Quercus petraea (Matt.) Liebl., Quercus robur L.) sampled on five sites with contrasting site conditions in pure and mixed stands and on trees of different social position. Measurements encompassed 1–7 years. Cumulative diameter increment was modelled by logistic mixed-effects models with random effects at the tree and year level. The results showed large differences in seasonal growth patterns between sites, with a clearly shorter growing season at the drier sites. Species specific response on dry sites could be linked to drought characteristics, whereas response on more humid sites was related to light requirements or successional status. The deciduous trees showed earlier growth culmination and shorter growing periods than the evergreen species. Individual tree growth of Quercus spp., P. abies, and F. sylvatica was positively affected by mixture whereas L. decidua, P. sylvestris and A. alba showed no or adverse mixture effects. Mixture effects differed between years and social position. Furthermore, increment culmination was earlier in mixed stands, but shifts were minor. Tree growth differed by social position with dominant trees showing the largest increment and the longest growth duration, with shifts in tree growth patterns due to social position being as large as those between different sites.

  • Strieder, Boku, University of Natural Resources and Life Sciences Vienna, Department of Forest- and Soil Sciences, Institute of Forest Growth, Peter-Jordan-Str. 82, A-1190 Vienna, Austria ORCID https://orcid.org/0000-0001-6398-8536 E-mail: emanuel.strieder@students.boku.ac.at
  • Vospernik, Boku, University of Natural Resources and Life Sciences Vienna, Department of Forest- and Soil Sciences, Institute of Forest Growth, Peter-Jordan-Str. 82, A-1190 Vienna, Austria ORCID http://orcid.org/0000-0002-4201-6444 E-mail: sonja.vospernik@boku.ac.at (email)
article id 10391, category Research article
Victoria A.M. Poljatschenko, Lauri T. Valsta. (2021). Carbon emissions displacement effect of Finnish mechanical wood products by dominant tree species in a set of wood use scenarios. Silva Fennica vol. 55 no. 1 article id 10391. https://doi.org/10.14214/sf.10391
Keywords: avoided emissions; mechanical forest industry; substitution effect; wooden construction
Highlights: Wood product consumption patterns are combined with production-based displacement factors to estimate displacement factors for logs by tree species; The main tree species in Finland have somewhat unequal displacement factors; Historical and projected wood use scenarios show large variation in the levels of avoided emissions between individual years and scenarios.
Abstract | Full text in HTML | Full text in PDF | Author Info

The carbon emissions displacement effect of Finnish logs for mechanical wood products by dominant tree species (Scots pine, Pinus sylvestris L.; Norway spruce, Picea abies (L.) H. Karst.; Birch, Betula spp.) was assessed by combining information from previous studies of current consumption patterns with displacement factors (DF) for structural construction, non-structural construction, and energy usage. We did not conduct additional life cycle analyses compared to the current literature. Our aim was to identify the factors that most extensively influence the displacement effect and to estimate the overall climate effect of Finnish logs in light of current production levels of mechanical forest industry. The analyses were based on information from both statistics and proprietary sources. Contrary to previous studies, we provide DFs by main tree species in Finland, which has been an unidentified area of research to date. Additionally, we apply a more detailed classification of structural and non-structural wood products. This study did not include effects on the forest carbon sink, as they depend case-wise on forest resources and forest management. According to our results, with current production and consumption trends, the average displacement effects for domestic Scots pine, Norway spruce, and birch logs were 1.28, 1.16, and 1.43 Mg C/Mg C, respectively. The corresponding overall annual displacement effect caused by the current production of sawn wood and wood-based panels was 12.3 Tg CO2 for Finland for the BAU scenario and varied between 8.6 and 16.3 Tg CO2 depending on the wood use scenario.

  • Poljatschenko, Simosol Oy, Hämeenkatu 10, FI-11100 Riihimäki, Finland E-mail: victoria.poljatschenko@simosol.fi (email)
  • Valsta, Department of Forest Sciences, University of Helsinki, Latokartanonkaari 7, FI-00014 University of Helsinki, Finland E-mail: lauri.valsta@helsinki.fi
article id 10351, category Research article
Karol Bronisz, Michał Zasada. (2020). Taper models for black locust in west Poland. Silva Fennica vol. 54 no. 5 article id 10351. https://doi.org/10.14214/sf.10351
Keywords: taper; Robinia pseudoacacia; mixed-effects models; section diameter over and under bark; volume prediction
Highlights: Seven taper models with different numbers of estimated parameters were analysed; Section diameter and volume was modelled using fixed and mixed-effects modelling approaches; The variable-form taper model with eight estimated parameters fitted the data the best; The lowest error for volume prediction was achieved for the fixed-effects taper model.
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The diameter at any point on a stem and tree volume are some of the most important types of information used in forest management planning. One of the methods to predict the diameter at any point on a stem is to develop taper models. Black locust (Robinia pseudoacacia L.) occurs in almost all forests in Poland, with the largest concentration in the western part of the country. Using empirical data obtained from 13 black locust stands (48 felled trees), seven taper models with different numbers of estimated parameters were analysed for section diameters both over and under bark using fixed and mixed-effects modelling approaches. Assuming a lack of additional measurements, the best fitted taper models were used for the prediction of over bark volume using both methods. The predicted volume was compared with the results from different volume equations available for black locust. The variable-form taper model with eight estimated parameters fitted the data the best. The lowest root mean square error for volume prediction was achieved for the elaborated fixed-effects taper model (0.0476), followed by the mixed-effects taper model (0.0489). At the same time, the difference between the volume relative errors achieved based on the taper models does not differ significantly from the results obtained using the volume equations already available for black locust (two of the three analysed).

  • Bronisz, Institute of Forest Sciences, Warsaw University of Life Sciences-SGGW, Nowoursynowska 159, PL 02-776 Warsaw, Poland E-mail: karol.bronisz@wl.sggw.pl (email)
  • Zasada, Institute of Forest Sciences, Warsaw University of Life Sciences-SGGW, Nowoursynowska 159, PL 02-776 Warsaw, Poland ORCID https://orcid.org/0000-0002-4881-296X E-mail: Michal.Zasada@wl.sggw.pl
article id 10242, category Research article
Shisheng Long, Siqi Zeng, Falin Liu, Guangxing Wang. (2020). Influence of slope, aspect and competition index on the height-diameter relationship of Cyclobalanopsis glauca trees for improving prediction of height in mixed forests. Silva Fennica vol. 54 no. 1 article id 10242. https://doi.org/10.14214/sf.10242
Keywords: secondary forest; effect; improved Hegyi_I; topographic feature; tree height estimation
Highlights: In this study, the effects of slope, aspect and competition index (CI) on the H-DBH relationship were explored and an improved CI was developed and included to improve predictions of Cyclobalanopsis glauca tree height; It was found that the effects were statistically significant and considering slope, aspect and CI for developing the H-DBH models significantly increased the H prediction accuracy.
Abstract | Full text in HTML | Full text in PDF | Author Info

Diameter at breast height (DBH) and height (H) of trees are two important variables used in forest management plans. However, collecting the measurements of H is time-consuming and costly. Instead, the H-DBH relationship is modeled and used to estimate H. But, ignoring the effects of slope, aspect and tree competition on the H-DBH relationship often impedes the improvement of H predictions. In this study, to improve predictions of Cyclobalanopsis glauca (Thunb.) Oerst. tree H in mixed forests, we compared eleven H-DBH models and examined the influence of slope and aspect on the H-DBH relationship using 426 trees. We then improved Hegyi competition index and explored its effect on the H predictions by including it in the selected models. Results showed 1) There were statistically significant effects of slope and aspect on the H-DBH relationship; 2) The log transformation and exponential model performed best for sunny- and shady-steep, respectively, and the Gompertz’s model was optimal for both sunny- and shady-gentle; 3) Compared with the whole dataset, the division of the data into the slope and aspect sub-datasets significantly reduced the RMSE of H predictions; 4) Compared with the selected models without competition index, adding the original Hegyi and improved Hegyi_I into the models improved the H predictions but only the models containing the improved Hegyi_I significantly increased the prediction accuracy at the significant level of 0.1. This study implied that modeling the H-DBH relationship under different slopes and aspects and including the improved Hegyi_I provided the great potential to improve the H predictions.

  • Long, Faculty of Forestry, Central South University of Forestry and Technology, Changsha, Hunan 410004, China E-mail: shisheng3604@21cn.com
  • Zeng, Faculty of Forestry, Central South University of Forestry and Technology, Changsha, Hunan 410004, China E-mail: zengsiqi@21cn.com
  • Liu, Faculty of Forestry, Central South University of Forestry and Technology, Changsha, Hunan 410004, China E-mail: liufl680@126.com
  • Wang, Research Center of Forestry Remote Sensing & Information Engineering, Central South University of Forestry and Technology, Changsha 410004, China; Department of Geography and Environmental Resources, Southern Illinois University, Carbondale, IL 62901, USA E-mail: gxwang@siu.edu (email)
article id 10036, category Research article
Karin Hjelm, Lars Rytter. (2018). The demand of hybrid aspen (Populus tremula × P. tremuloides) on site conditions for a successful establishment on forest land. Silva Fennica vol. 52 no. 5 article id 10036. https://doi.org/10.14214/sf.10036
Keywords: regeneration; site preparation; clone effects; poplars; soil acidity
Highlights: Low pH (below 3.5) reduced growth, but not survival, in a greenhouse study; Site preparation methods did not affect survival in field, but differences were found for growth; Mounding had generally the best effect on growth; Clonal differences were found that could be useful for improving establishment and growth.
Abstract | Full text in HTML | Full text in PDF | Author Info

Hybrid aspen (Populus tremula L. × P. tremuloides Michx.) is a deciduous tree species suitable for producing large amounts of renewable biomass during short rotations. Its potential under North European conditions could be largely extended if not only agricultural land but also forest land was used for cultivation. Unfortunately, the knowledge of appropriate forest site conditions and effects of site preparation methods on hybrid aspen establishment is limited. In this paper, two studies that explore these questions are presented. In the first study, the sensitivity to acid soils was tested under greenhouse conditions in two type of soils: a) peat soil limed to certain pH levels (3.4–5.7) and b) collected forest soils where pH varied from 3.9 to 5.3. The lowest pH level resulted in reduced growth, elsewhere no significant differences were found. The second study was applied in the field and investigated the effect of four site preparation methods on survival and growth. The methods were: 1) control with no site preparation, 2) patch scarification, 3) mounding and 4) soil inversion. While no differences were found for survival, mounding was generally the method with the highest growth and patch scarification was least successful. The result was probably an effect of good soil aeration and less competition from vegetation after mounding. The field study also revealed clonal differences in growth performance, which stresses the importance of clone selection prior to planting. The results of these studies indicate that hybrid aspen is less sensitive to variation in pH and site preparation methods compared with other poplar species, as have been found in similar studies.

  • Hjelm, Skogforsk, Ekebo 2250, SE-268 90 Svalöv, Sweden E-mail: karin.hjelm@skogforsk.se (email)
  • Rytter, Skogforsk, Ekebo 2250, SE-268 90 Svalöv, Sweden ORCID http://orcid.org/0000-0001-6183-4832 E-mail: lars.rytter@skogforsk.se
article id 10013, category Research article
Hardo Becker, Jürgen Aosaar, Mats Varik, Gunnar Morozov, Kristiina Aun, Ülo Mander, Kaido Soosaar, Veiko Uri. (2018). Annual net nitrogen mineralization and litter flux in well-drained downy birch, Norway spruce and Scots pine forest ecosystems. Silva Fennica vol. 52 no. 4 article id 10013. https://doi.org/10.14214/sf.10013
Keywords: Pinus sylvestris; Picea abies; Betula pubescens; drained peatland forests; ammonification; effect of tree species; swamp; nitrification; transitional bog
Highlights: The net nitrogen mineralization (NNM) flux in drained peat soils depends largely on the C/N ratio and tree species; The soil NNM process is affected by trees through organic litter input into soil; Pine stand in low-fertility drained transitional bog is dominated by net ammonification; Birch and spruce stands on the fertile drained peat soil with higher pH and N content are dominated by net nitrification.
Abstract | Full text in HTML | Full text in PDF | Author Info

The main aim of the current study was to estimate the annual net nitrogen mineralization (NNM) flux in stands of different tree species growing on drained peatlands, as well as to clarify the effect of tree species, soil properties and litter on annual NNM dynamics. Three study sites were set up in May 2014: a downy birch (Betula pubescens Ehrh.) stand and a Norway spruce (Picea abies (L.) Karst.) stand in Oxalis full-drained swamp (ODS) and a Scots pine (Pinus sylvestris L.) stand in Myrtillus full-drained swamp (MDS). The NNM flux was estimated using the in situ method with incubated polyethylene bags. The highest value of NNM was found in stands that were growing on fertile ODS: 127.5 kg N ha–1 yr–1 and 87.7 kg N ha–1 yr–1, in the downy birch stand and in the Norway spruce stand, respectively. A significantly lower annual NNM flux (11.8 kg N ha–1 yr–1) occurred in the Scots pine stand growing in MDS. Nitrification was highest at fertile ODS sites and ammonification was the highest at the low fertility MDS site. For all study sites, positive correlation was found between soil temperature and NNM intensity. The difference in annual NNM between the downy birch stand and the Norway spruce stand growing on similar drained fertile peatlands was due to litter quality. The annual N input into the soil through leaf litter was the highest at the downy birch site where also the C/N ratio of litter was the lowest. The second highest N input into the soil was found in the spruce stand and the lowest in the pine stand.

  • Becker, Chair of Silviculture and Forest Ecology, Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, Friedrich Reinhold Kreutzwaldi 1, 51014 Tartu, Estonia E-mail: hardo.becker@emu.ee (email)
  • Aosaar, Chair of Silviculture and Forest Ecology, Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, Friedrich Reinhold Kreutzwaldi 1, 51014 Tartu, Estonia E-mail: jyrgen.aosaar@emu.ee
  • Varik, Chair of Silviculture and Forest Ecology, Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, Friedrich Reinhold Kreutzwaldi 1, 51014 Tartu, Estonia E-mail: mats.varik@emu.ee
  • Morozov, Chair of Silviculture and Forest Ecology, Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, Friedrich Reinhold Kreutzwaldi 1, 51014 Tartu, Estonia E-mail: gunnar.morozov@emu.ee
  • Aun, Chair of Silviculture and Forest Ecology, Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, Friedrich Reinhold Kreutzwaldi 1, 51014 Tartu, Estonia E-mail: kristiina.aun@emu.ee
  • Mander, Department of Geography, Institute of Ecology & Earth Sciences, University of Tartu, Ülikooli 18, 50090 Tartu, Estonia E-mail: ulo.mander@ut.ee
  • Soosaar, Department of Geography, Institute of Ecology & Earth Sciences, University of Tartu, Ülikooli 18, 50090 Tartu, Estonia E-mail: kaido.soosaar@ut.ee
  • Uri, Chair of Silviculture and Forest Ecology, Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, Friedrich Reinhold Kreutzwaldi 1, 51014 Tartu, Estonia E-mail: veiko.uri@emu.ee
article id 10006, category Research article
Matti Maltamo, Tomi Karjalainen, Jaakko Repola, Jari Vauhkonen. (2018). Incorporating tree- and stand-level information on crown base height into multivariate forest management inventories based on airborne laser scanning. Silva Fennica vol. 52 no. 3 article id 10006. https://doi.org/10.14214/sf.10006
Keywords: forest inventory; LIDAR; alpha shape; crown height; nearest neighbor; mixed-effects model
Highlights: The most accurate tree-level alternative is to include crown base height (CBH) to nearest neighbour imputation; Also mixed-effects models can be applied to predict CBH using tree attributes and airborne laser scanning (ALS) metrics; CBH prediction can be included with an accuracy of 1–1.5 m to forest management inventory applications.
Abstract | Full text in HTML | Full text in PDF | Author Info

This study examines the alternatives to include crown base height (CBH) predictions in operational forest inventories based on airborne laser scanning (ALS) data. We studied 265 field sample plots in a strongly pine-dominated area in northeastern Finland. The CBH prediction alternatives used area-based metrics of sparse ALS data to produce this attribute by means of: 1) Tree-level imputation based on the k-nearest neighbor (k-nn) method and full field-measured tree lists including CBH observations as reference data; 2) Tree-level mixed-effects model (LME) prediction based on tree diameter (DBH) and height and ALS metrics as predictors of the models; 3) Plot-level prediction based on analyzing the computational geometry and topology of the ALS point clouds; and 4) Plot-level regression analysis using average CBH observations of the plots for model fitting. The results showed that all of the methods predicted CBH with an accuracy of 1–1.5 m. The plot-level regression model was the most accurate alternative, although alternatives producing tree-level information may be more interesting for inventories aiming at forest management planning. For this purpose, k-nn approach is promising and it only requires that field measurements of CBH is added to the tree lists used as reference data. Alternatively, the LME-approach produced good results especially in the case of dominant trees.

  • Maltamo, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: matti.maltamo@uef.fi (email)
  • Karjalainen, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: tomimkarjalainen@gmail.com
  • Repola, Natural Resources Institute of Finland (Luke), Natural resources, Eteläranta 55, FI-96300 Rovaniemi, Finland E-mail: jaakko.repola@luke.fi
  • Vauhkonen, Natural Resources Institute of Finland (Luke), Bioeconomy and environment, Yliopistokatu 6, 80100 Joensuu, Finland E-mail: jari.vauhkonen@luke.fi
article id 7783, category Research article
Markku T. Lehtinen, Pertti Pulkkinen. (2017). Effects of Scots pine paternal genotypes of two contiguous seed orchards on the budset and frost hardening of first-year progeny. Silva Fennica vol. 51 no. 5 article id 7783. https://doi.org/10.14214/sf.7783
Keywords: Pinus sylvestris; provenance; conifer; environmental influence; pollen; genotype effect
Highlights: This environmentally controlled study on Scots pine demonstrated the effect of the paternal genotype on the budset and frost hardening of the progeny; With the applied study design, no significant indication of an environmental influence on the effect of the Scots pine paternal genotype was obtained.
Abstract | Full text in HTML | Full text in PDF | Author Info

In Scots pine (Pinus sylvestris L.), it has been shown that the parental conditions have a role in the phenological variation among first-year seedlings. For this reason, it is argued that they should be comprehensively controlled before estimating the parental genotype effects. This controlled-cross study examined the effects of a set of fathers of Scots pines on the timing of budset and autumn frost hardening of first-year seedlings. The paternal genotypes had either a northern or southern provenance, but had spent a period of over 25 years as grafts in a shared climatic environment in two closely located southern orchards. Pollen applied in the crosses was collected from these orchards in one year and all the maternal genotypes were pollinated in only one seed orchard. The results of freeze tests and budset observations of the consequent progeny were analysed and additionally compared with results obtained using seedlings from seed lots of natural forests in order to estimate the ability of northern paternal genotypes to maintain a northern effect under southern conditions. This environmentally controlled study demonstrated a significant effect of the paternal genotype on the budset and autumn frost hardening of first-year seedling of Scots pine. With the applied study design, no significant indication of an environmental influence on the effect of the paternal genotype was obtained. The accuracy of the observations is discussed. It is concluded that the results suggest a minor role of mutability in the effects of Scots pine paternal genotypes.

  • Lehtinen, University of Helsinki, Department of Agricultural Sciences, Latokartanonkaari 5 and 7, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: markku.t.lehtinen@helsinki.fi (email)
  • Pulkkinen, Natural Resources Institute Finland (Luke), Green Technology, Haapastensyrjäntie 34, FI-12600 Läyliäinen, Finland E-mail: pertti.pulkkinen@luke.fi
article id 1740, category Research article
Ram P. Sharma, Zdeněk Vacek, Stanislav Vacek. (2017). Modelling tree crown-to-bole diameter ratio for Norway spruce and European beech. Silva Fennica vol. 51 no. 5 article id 1740. https://doi.org/10.14214/sf.1740
Keywords: Picea abies; Fagus sylvatica; dominant height; exponential decay function; mixed effect model; spatially explicit competition index; species proportion; species mixture effect
Highlights: Modelled crown-to-bole diameter ratio (CDBDR) using tree and stand-level predictors, and sample plot random effects; Spatially explicit mixed-effects model described the largest part of CDBDR variation with no significant trend in the residuals; The CDBDR increased with increasing stand development stage and site quality, but decreased with decreasing proportion of the species of interest, and increasing competition.
Abstract | Full text in HTML | Full text in PDF | Author Info

Crown dimensions are correlated to growth of other parts of a tree and often used as predictors in growth models. The crown-to-bole diameter ratio (CDBDR), which is a ratio of maximum crown width to diameter at breast height (DBH), was modelled using data from permanent sample plots located on Norway spruce (Picea abies (L.) Karst.) and European beech (Fagus sylvatica L.) stands in different parts of the Czech Republic. Among various tree and stand-level measures evaluated, DBH, height to crown base (HCB), dominant height (HDOM), basal area of trees larger in diameter than a subject tree (BAL), basal area proportion of the species of interest (BAPOR), and Hegyi’s competition index (CI) were found to be significant predictors in the CDBDR model. Random effects were included using the mixed-effects modelling to describe sample plot-level variation. For each species, the mixed-effects model described a larger part of the variation of the CDBDR than nonlinear ordinary least squares model with no trend in the residuals. The spatially explicit mixed-effects model showed more attractive fit statistics [conditional R2 ≈ 0.73 (spruce), 0.78 (beech)] than its spatially inexplicit counterpart [conditional R2 ≈ 0.71 (spruce), 0.76 (beech)]. The model showed that CDBDR increased with increasing HDOM – a measure that combines the stand development stage and site quality – but decreased with increasing HCB and competition (increasing BAL and CI), and decreasing proportions of the species of interest (increasing BAPOR). For both species, the spatially explicit mixed-effects model should be a preferred choice for a precise prediction of the CDBDR. The CDBDR model will have various management implications such as determination of spacing, stand basal area, stocking, and planning of appropriate species mixture.

  • Sharma, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague, Kamýcká 129, 16521, Praha 6 – Suchdol, Czech Republic E-mail: sharmar@fld.czu.cz (email)
  • Vacek, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague, Kamýcká 129, 16521, Praha 6 – Suchdol, Czech Republic E-mail: vacekz@fld.czu.cz
  • Vacek, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague, Kamýcká 129, 16521, Praha 6 – Suchdol, Czech Republic E-mail: vacekstanislav@fld.czu.cz
article id 1566, category Research article
Valdir Marcos Stefenon, Jordana Caroline Nagel, Igor Poletto. (2016). Evidences of genetic bottleneck and fitness decline in Luehea divaricata populations from southern Brazil. Silva Fennica vol. 50 no. 5 article id 1566. https://doi.org/10.14214/sf.1566
Keywords: demographic history; effective population size; genetic resources conservation; Pampa biome
Highlights: Signatures of genetic bottlenecks and reduction of populations’ fitness were observed in populations of Luehea divaricata in southern Brazil; Lower levels of observed heterozygosity are correlated with populations’ fitness, decreasing germination capacity and increasing the proportion of anomalous germinated plantlets; Promoting the connection among populations is proposed as a key strategy towards conservation of L. divaricata genetic resources in its southernmost distribution range.
Abstract | Full text in HTML | Full text in PDF | Author Info

Extant populations growing in regions that were refugia during the last glacial period are expected to show higher genetic diversity than populations that moved from these refugia into new areas in higher latitudes. Such new populations likely faced harsher climatic conditions, being established with reduced population size and experiencing the effects of genetic bottlenecks. In this study we employed data from nuclear SSR markers for detecting molecular signatures of genetic bottlenecks, and germination experiments to evaluate reduction of populations’ fitness in natural populations of Luehea divaricata Mart. et Zucc., growing in the southern range of the species distribution (around 30°S latitude). Signatures of genetic bottlenecks and reduction of populations’ fitness were observed in all populations. Lower levels of observed heterozygosity are correlated with populations’ fitness, decreasing germination capacity and increasing the proportion of anomalous germinated plantlets. Promoting the connection among populations is proposed as a key strategy towards conservation of L. divaricata genetic resources in its southernmost distribution range. The offspring from crosses among populations would significantly increase the observed heterozygosity and fitness of multiple populations.

  • Stefenon, Nucleus of Genomics and Molecular Ecology, Interdisciplinary Center of Biotechnological Research, Universidade Federal do Pampa, BR290 km, 97300-000, São Gabriel, RS, Brazil E-mail: valdirstefenon@unipampa.edu.br (email)
  • Nagel, Nucleus of Genomics and Molecular Ecology, Interdisciplinary Center of Biotechnological Research, Universidade Federal do Pampa, BR290 km, 97300-000, São Gabriel, RS, Brazil E-mail: jordana.nagel@yahoo.com.br
  • Poletto, Laboratory of Plant Protection, Universidade Federal do Pampa, BR290 km, 97300-000, São Gabriel, RS, Brazil E-mail: igorpoletto@unipampa.edu.br
article id 1567, category Research article
Eetu Kotivuori, Lauri Korhonen, Petteri Packalen. (2016). Nationwide airborne laser scanning based models for volume, biomass and dominant height in Finland. Silva Fennica vol. 50 no. 4 article id 1567. https://doi.org/10.14214/sf.1567
Keywords: forest inventory; LIDAR; regression analysis; remote sensing; calibration; area-based approach; mixed-effect models
Highlights: Pooled data from nine inventory projects in Finland were used to create nationwide laser-based regression models for dominant height, volume and biomass; Volume and biomass models provided regionally different means than real means, but for dominant height the mean difference was small; The accuracy of general volume predictions was nevertheless comparable to relascope-based field inventory by compartments.
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The aim of this study was to examine how well stem volume, above-ground biomass and dominant height can be predicted using nationwide airborne laser scanning (ALS) based regression models. The study material consisted of nine practical ALS inventory projects taken from different parts of Finland. We used field sample plots and airborne laser scanning data to create nationwide and regional models for each response variable. The final models had one or two ALS predictors, which were chosen based on the root mean square error (RMSE), and cross-validated. Finally, we tested how much predictions would improve if the nationwide models were calibrated with a small number of regional sample plots. Although forest structures differ among different parts of Finland, the nationwide volume and biomass models performed quite well (leave-inventory-area-out RMSE 22.3% to 33.8%, mean difference [MD] –13.8% to 18.7%) compared with regional models (leave-plot-out RMSE 20.2% to 26.8%). However, the nationwide dominant height model (RMSE 5.4% to 7.7%, MD –2.0% to 2.8%, with the exception of the Tornio region – RMSE 11.4%, MD –9.1%) performed nearly as well as the regional models (RMSE 5.2% to 6.7%). The results show that the nationwide volume and biomass models provided different means than real means at regional level, because forest structure and ALS device have a considerable effect on the predictions. Large MDs appeared especially in northern Finland. Local calibration decreased the MD and RMSE of volume and biomass models. However, the nationwide dominant height model did not benefit much from calibration.

  • Kotivuori, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: eetu.kotivuori@uef.fi (email)
  • Korhonen, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: lauri.korhonen@uef.fi
  • Packalen, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: petteri.packalen@uef.fi
article id 1448, category Research article
Andrew McEwan, Natascia Magagnotti, Raffaele Spinelli. (2016). The effects of number of stems per stool on cutting productivity in coppiced Eucalyptus plantations. Silva Fennica vol. 50 no. 2 article id 1448. https://doi.org/10.14214/sf.1448
Keywords: modeling; logging; short rotation forestry; efficiency; operator effect
Highlights: Double- and single stem coppice stools were harvested mechanically; Stem size had the strongest impact on productivity; An experienced operator performed equally well with both stool treatments; Cost was ~10% higher with double stems for the less experienced operator; Operator experience may play a major role when cutting coppice stands.
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A time study was conducted to determine whether stem crowding had any impact on harvester productivity in Eucalyptus grandis stands. This represents an important element when trying to balance the advantages and disadvantages of coppice management in fast growing plantations designated for mechanized harvesting (i.e. machine felling, delimbing, debarking and cross-cutting). The study material consisted of 446 coppice stems, half of which grew as single stems per stool and half as double stems per stool as a result of different coppice reduction strategies. The dataset was balanced and randomized, with both subsets replicating exactly the same stem size distribution and the single and double stems alternating randomly. Harvester productivity ranged between 6 and 50 m3 under bark per productive machine hour, following the variation of tree diameter from 10 to 40 cm at breast height (1.37 m according to South African standards). Regression analysis indicated that both tree size and stem crowding (e.g. one or two stems per stool) had a significant effect on harvester productivity, which increased with stem size and decreased with stem crowding. However, operator experience may overcome the effect of stem crowding, which was not significant when the harvester was manned by a highly experienced operator. In any case, the effect of stem size was much greater than that of stem crowding, which resulted in a cost difference of less than 10%. However, this figure excludes the possible effects of stem crowding on volume recovery and stem development, which should be addressed in the future.

  • McEwan, Nelson Mandela Metropolitan University – George Campus, Saasveld, 6529, George, South Africa E-mail: Andrew.McEwan@nmmu.ac.za
  • Magagnotti, CNR IVALSA, Via Madonna del Piano 10, I-50019 Sesto Fiorentino (FI), Italy E-mail: magagnotti@ivalsa.cnr.it
  • Spinelli, CNR IVALSA, Via Madonna del Piano 10, I-50019 Sesto Fiorentino (FI), Italy E-mail: spinelli@ivalsa.cnr.it (email)
article id 1342, category Research article
Blas Mola-Yudego, Gianni Picchi, Dominik Röser, Raffaele Spinelli. (2015). Assessing chipper productivity and operator effects in forest biomass operations. Silva Fennica vol. 49 no. 5 article id 1342. https://doi.org/10.14214/sf.1342
Keywords: mixed models; efficiency; comminution; operator effect; raw material supply; wood chippers
Highlights: A model is constructed to assess the productivity in chipping of wood biomass at roadside; The data includes 172 trials and 67 operators in Italy; The operator effect was included in a mixed model approach; The R2 were 0.76 (fixed part) and 0.88 (incl. operator effects).
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The present research focuses on the productivity of energy wood chipping operations at several sites in Italy. The aim was to assess the productivity and specifically the effect attributed to the operator in the chipping of wood biomass. The research included 172 trials involving 67 operators across the country that were analysed using a mixed model approach, in order to assess productivity, and to isolate the operator effect from other potential variables. The model was constructed using different predictors aiming to explain the variability due to the machines and the raw-materials. The final model included the average piece weight of raw material chipped as well as the power of the machine. The coefficients of determination (R2) were 0.76 for the fixed part of the model, and 0.88 when the effects due to the operators were included. The operators’ performance compared to their peers was established, and it was compared to a subjective classification based on the operator’s previous experience. The results of this study can help to the planning and logistics of raw material supply for bioenergy, as well as to a more effective training of future forest operators.

  • Mola-Yudego, School of Forest Sciences, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland; NIBIO Norwegian Institute of Bioeconomy Research, P.O. Box 115, 1431 Ås, Norway ORCID http://orcid.org/0000-0003-0286-0170 E-mail: blas.mola@uef.fi (email)
  • Picchi, CNR IVALSA, Via Madonna del Piano 10, I-50019 Sesto Fiorentino, Italy E-mail: picchi@ivalsa.cnr.it
  • Röser, Forest Feedstocks Group, FPInnovations, Vancouver, British Columbia, Canada E-mail: dominik.roser@fpinnovations.ca
  • Spinelli, CNR IVALSA, Via Madonna del Piano 10, I-50019 Sesto Fiorentino, Italy E-mail: spinelli@ivalsa.cnr.it
article id 1087, category Research article
Ilkka Korpela, Lauri Mehtätalo, Lauri Markelin, Anne Seppänen, Annika Kangas. (2014). Tree species identification in aerial image data using directional reflectance signatures. Silva Fennica vol. 48 no. 3 article id 1087. https://doi.org/10.14214/sf.1087
Keywords: forestry; reflectance calibration; BRDF; mixed-effects modeling; Monte-Carlo simulation
Highlights: Multispectral reflectance data showed a strong and spectrally correlated tree effect; There was no gain in species classification from using species-specific differences of directional reflectance in real data and only a marginal improvement in simulated data; The directional signatures extracted in multiple images are obscured by the intrinsic within-species variation, correlated observations and inherent reflectance calibration errors.
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Tree species identification using optical remote sensing is challenging. Modern digital photogrammetric cameras enable radiometrically quantitative remote sensing and the estimation of reflectance images, in which the observations depend largely on the reflectance properties of targets. Previous research has shown that there are species-specific differences in how the brightness observed changes when the viewing direction in an aerial image is altered. We investigated if accounting for such directional signatures enhances species classification, using atmospherically corrected, real and simulated multispectral Leica ADS40 line-camera data. Canopy in direct and diffuse illumination were differentiated and species-specific variance-covariance structures were analyzed in real reflectance data, using mixed-effects modeling. Species classification simulations aimed at elucidating the level of accuracy that can be achieved by using images of different quality, number and view-illumination geometry. In real data, a substantial variance component was explained by tree effect, which demonstrates that observations from a tree correlate between observation geometries as well as spectrally. Near-infrared band showed the strongest tree effect, while the directionality was weak in that band. The gain from directional signatures was insignificant in real data, while simulations showed a potential gain of 1–3 percentage points in species classification accuracy. The quality of reflectance calibration was found to be important as well as the image acquisition geometry. We conclude that increasing the number of image observations cancels out random observation noise and reflectance calibration errors, but fails to eliminate the tree effect and systematic calibration inaccuracy. Directional reflectance constitutes a marginal improvement in tree species classification.
  • Korpela, Department of Forest Sciences, University of Helsinki, P.O. Box 27, FI-00014, Finland E-mail: ilkka.korpela@helsinki.fi (email)
  • Mehtätalo, Faculty of Science and Forestry, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: lauri.mehtatalo@uef.fi
  • Markelin, Department of Remote Sensing and Photogrammetry, Finnish Geodetic Institute, P.O. Box 15, FI-02431 Masala, Finland E-mail: lauri.markelin@fgi.fi
  • Seppänen, Faculty of Science and Forestry, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: anne.seppanen@arbonaut.com
  • Kangas, Department of Forest Sciences, University of Helsinki, P.O. Box 27, FI-00014, Finland E-mail: annika.kangas@helsinki.fi
article id 919, category Research article
Karri Uotila, Juho Rantala, Timo Saksa. (2012). Estimating the need for early cleaning in Norway spruce plantations in Finland. Silva Fennica vol. 46 no. 5 article id 919. https://doi.org/10.14214/sf.919
Keywords: cleaning; conifer release; cost-effectiveness; forest vegetation management; early cleaning
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Effective management of Norway spruce (Picea abies (L.) Karst.) plantations requires detailed information on stand development, which is costly to measure. However, estimating the need for early stand management from site attributes that persists stabile after ones measured, may provide an inexpensive alternative. This study compared hardwood competition in spruce plantations of varying ages and tested the usability of this information in estimating the need for early cleaning. The data included 197 spruce plantations (4–7 years old) inventoried in southern Finland in 2007. The level (Low, Substantial, High) of need for early cleaning was subjectively determined by contrasting location and size of competing hardwoods to a conifer crop tree. Then the stage of the need for early cleaning was modelled according to site and stand attributes. Nearly 60% of the conifer crop trees in the plantations were subjectively judged to require early cleaning (Substantial 37.2%, High 21.2%), but only 10 per cent of the evaluated area was cleaned. Need for cleaning was intense on peatlands or damp soils, whereas it was mild on unprepared soils or cleaned sites. Traditional site characteristics used in forest management planning can be useful for recognising the peripheral cases, where need for cleaning is probably high or low. However, on a typical mineral soil plantation (uncleaned, soil prepared) the model indicates the differences in the need for early cleaning weakly. The need for early cleaning was already high in 4-year-old plantations, why stand age did not have significant effect on development of the need. Thus, the timing of an operation can not be predicted with the model. Nonetheless, early cleaning very likely opens growth space of crop trees in a 4–7-year-old spruce plantation. Therefore, from an aspect of crop growth, an uncleaned Norway spruce plantation in this age group is quite consistently worth cleaning.
  • Uotila, Finnish Forest Research Institute, Suonenjoki Unit, Juntintie 154, FI-77600 Suonenjoki, Finland E-mail: karri.uotila@metla.fi (email)
  • Rantala, Metsä Group, Tampere, Finland E-mail: juho.rantala@metsagroup.com
  • Saksa, Finnish Forest Research Institute, Suonenjoki Unit, Juntintie 154, FI-77600 Suonenjoki, Finland E-mail: timo.saksa@metla.fi
article id 157, category Research article
Ville Kankaanhuhta, Timo Saksa, Heikki Smolander. (2010). The effect of quality management on forest regeneration activities in privately-owned forests in southern Finland. Silva Fennica vol. 44 no. 2 article id 157. https://doi.org/10.14214/sf.157
Keywords: silvicultural operations; quality control; program evaluation; program effectiveness
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This study describes the effect of quality management on forest regeneration activities in privately-owned forests in southern Finland. The study material consists of two mail surveys conducted in 2006 and 2007. The questionnaires were sent to forestry professionals in Forest Owners’ Associations (FOAs), who had either participated (participants) or not (non-participants) in the forest regeneration quality management interventions in years 2000–2006. Quality management interventions of the FOAs included field inventories, feedback meetings, and education sessions about quality techniques. The activities of participant and non-participant FOAs were compared in terms of the available resources, the actions taken, and the aspirations for improvement. In the FOAs, which had participated in quality management, the number of excavator contractors had increased by 16% more than in the non-participant FOAs. The contractors had acquired 23% more soil preparation equipment under the supervision of the participant forestry professionals. The soil preparation method used in conjunction with Norway spruce that had most increased in use was patch mounding. Seedlings that were 1.5 years and older were used by participant forestry professionals in the planting of Norway spruce 11% more than by non-participants. The planting workers had attended 14% more educational sessions, while the use of self-control measurements in soil preparation and planting density had been adopted 10% more frequently under the supervision of the forestry professionals participating in the quality management. A greater interest in obtaining feedback by using quality control inventories was also found among forestry professionals who participated in quality management.
  • Kankaanhuhta, Finnish Forest Research Institute, Juntintie 154, FI-77600 Suonenjoki, Finland E-mail: ville.kankaanhuhta@metla.fi (email)
  • Saksa, Finnish Forest Research Institute, Juntintie 154, FI-77600 Suonenjoki, Finland E-mail: ts@nn.fi
  • Smolander, Finnish Forest Research Institute, Juntintie 154, FI-77600 Suonenjoki, Finland E-mail: hs@nn.fi
article id 213, category Research article
Bum-Jin Park, Yuko Tsunetsugu, Tamami Kasetani, Takeshi Morikawa, Takahide Kagawa, Yoshifumi Miyazaki. (2009). Physiological effects of forest recreation in a young conifer forest in Hinokage Town, Japan. Silva Fennica vol. 43 no. 2 article id 213. https://doi.org/10.14214/sf.213
Keywords: blood pressure; heart rate variability; pulse rate; relaxation; Shinrin-yoku; therapeutic effects of forest; well-being
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It is widely believed that coming into contact with forest environments is somehow beneficial to human well-being and comfort. In Japan, “Shinrin-yoku” (taking in the atmosphere of a forest) has been proposed to be a relaxation activity associated with forest recreation. The purpose of this study was to examine the physiological effects of forest recreation on the autonomic nervous activity. The subjects were twelve male university students (21.8 ± 0.8 years old). On the first day of the experiment, six subjects were sent to a forest area, and the other six to a city area. On the second day, each subject was sent to the area he did not visit on the first day as a cross check. The subjects walked (15 minutes) around their assigned areas before noon, and sat on chairs viewing (15 minutes) the landscapes of their assigned areas in the afternoon. Heart rate variability (HRV), blood pressure, and pulse rate were measured as physiological indices. Measurements were taken at the place of accommodation in the morning, before and after walking, and before and after viewing at their assigned field areas. Pulse rate, diastolic blood pressure and LF/(LF+HF) (LF – low frequency, HF – high frequency) components of HRV were significantly lower in the forest area than in the city area. HF components of HRV tended to be higher in the forest than in the city. In conclusion, the results of the physiological measurements show that forest recreation enabled effective relaxation in people, both of the mind and body.
  • Park, Chiba University, Center for Environment, Health and Field Sciences, Kashiwa-no-ha 6-2-1, 277-0882 Kashiwa, Chiba, Japan E-mail: bjpark@faculty.chiba-u.jp (email)
  • Tsunetsugu, Chiba University, Center for Environment, Health and Field Sciences, Kashiwa-no-ha 6-2-1, 277-0882 Kashiwa, Chiba, Japan E-mail: yt@nn.jp
  • Kasetani, Chiba University, Center for Environment, Health and Field Sciences, Kashiwa-no-ha 6-2-1, 277-0882 Kashiwa, Chiba, Japan E-mail: tk@nn.jp
  • Morikawa, Chiba University, Center for Environment, Health and Field Sciences, Kashiwa-no-ha 6-2-1, 277-0882 Kashiwa, Chiba, Japan E-mail: tm@nn.jp
  • Kagawa, Chiba University, Center for Environment, Health and Field Sciences, Kashiwa-no-ha 6-2-1, 277-0882 Kashiwa, Chiba, Japan E-mail: tk@nn.jp
  • Miyazaki, Chiba University, Center for Environment, Health and Field Sciences, Kashiwa-no-ha 6-2-1, 277-0882 Kashiwa, Chiba, Japan E-mail: ym@nn.jp
article id 227, category Research article
Ola Lindroos. (2008). The effects of increased mechanization on time consumption in small-scale firewood processing. Silva Fennica vol. 42 no. 5 article id 227. https://doi.org/10.14214/sf.227
Keywords: comparative time study; fuelwood; blade saw; wedge splitter; processor; senior worker; operator effects
Abstract | View details | Full text in PDF | Author Info
Firewood, which is mainly processed by the consumer, is still an important source of energy for heating houses in industrialised countries. Possibilities to compare the mechanization’s impact on efficiency of firewood processing are limited, due to variations between working conditions in previous studies. Therefore, the objective was to compare time consumption for two small-scale firewood processing systems with different levels of mechanisation under identical conditions. The systems were tested on two classes of wood: one with a homogeneous and medium-sized diameter of logs and one with a mixture of small and large-diameter-logs. Differences in time consumption were analysed for correlations with physical workloads, deviations to routine operations, operator influences and operator perceptions. Twelve operators (60–79 years old) were studied and they showed large variation in time consumption. However, the within-operator time consumption patterns were consistent. In other words, operators all responded similarly to the different combinations of systems and wood classes, but at different absolute levels. The time required to process a unit volume of wood was 25–33% lower when the more highly mechanised system was used, and the time required was 13–22% lower for the homogeneous wood class. Physical work load, deviations and perceptions of the work varied between operators, but were weakly correlated with time consumption. The results’ implications for analyses of investments in equipment for firewood-processing for self-sufficiency purposes are discussed.
  • Lindroos, Swedish University of Agricultural Sciences, Department of Forest Resource Management, SE-901 83 Umeå, Sweden E-mail: ola.lindroos@srh.slu.se (email)
article id 264, category Research article
Yrjö Nuutinen, Kari Väätäinen, Jaakko Heinonen, Antti Asikainen, Dominik Röser. (2008). The accuracy of manually recorded time study data for harvester operation shown via simulator screen. Silva Fennica vol. 42 no. 1 article id 264. https://doi.org/10.14214/sf.264
Keywords: accuracy of timing; mixed effects models; time studies
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The aim of the study was to investigate the effect of work experience on the accuracy and variation of observers recording the operation time of a harvester. A simulated thinning operation using a harvester, shown as video via a television screen in laboratory conditions, was observed by 20 inexperienced students and 10 experienced work study researchers. All the observers timed the different work elements of the harvester work with special fieldwork timers. The duration of different work elements measured by the human observers were compared to the corresponding recordings by the harvester’s automated data collector. Although the inexperienced students made more measurement mistakes than the experienced researchers, the differences in measurement error averages were not statistically significant between the groups. However, the variances of tree specific errors were significantly higher in the measurements done by the students. As inexperienced recorders, the students were not able to properly record short work elements, which lasted a maximum of 4 seconds. Due to systematic measurement errors, there was a large variation in the timing structures of the work elements among all observers. Observers’ skills and experience seems to affect measurement accuracy and thus the derived results, especially in intensive time studies. Therefore, the recorder should receive detailed training and practical experience in timing of different work elements of forest operations. In the future, with the use of automated data collectors time studies with large, detailed and accurate data will be implemented. However, due to the varying timing conditions in the forest, manual data collection is still required because of its greater flexibility.
  • Nuutinen, Finnish Forest Research Institute, Joensuu Research Unit, P.O. Box 68, FI-80101 Joensuu, Finland E-mail: yrjo.nuutinen@metla.fi (email)
  • Väätäinen, Finnish Forest Research Institute, Joensuu Research Unit, P.O. Box 68, FI-80101 Joensuu, Finland E-mail: kv@nn.fi
  • Heinonen, Finnish Forest Research Institute, Joensuu Research Unit, P.O. Box 68, FI-80101 Joensuu, Finland E-mail: jh@nn.fi
  • Asikainen, Finnish Forest Research Institute, Joensuu Research Unit, P.O. Box 68, FI-80101 Joensuu, Finland E-mail: aa@nn.fi
  • Röser, Finnish Forest Research Institute, Joensuu Research Unit, P.O. Box 68, FI-80101 Joensuu, Finland E-mail: dr@nn.fi
article id 331, category Research article
Jouni Siipilehto. (2006). Height distributions of Scots pine sapling stands affected by retained tree and edge stand competition. Silva Fennica vol. 40 no. 3 article id 331. https://doi.org/10.14214/sf.331
Keywords: Pinus sylvestris; retention; height distribution; Weibull function; percentile prediction; edge effect
Abstract | View details | Full text in PDF | Author Info
The paper focused on the height structure of Scots pine saplings affected by (1) retained solitary pine trees or (2) a pine-dominated edge stand. The study material in (1) and (2) consisted of ten separate regeneration areas in southern Finland. In (1) 2-m radius study plots were located at 1, 3, 6 and 10 m distances from 10 systematically selected, solitary retained trees in each stand. In (2) the study plots were systematically located within 20 m from the edge stand. Competition of the individual trees was modelled using ecological field theory. The 24th and 93rd sample percentiles were used for estimating the height distribution using the two-parameter Weibull function. The models incorporated the effect of varying advanced tree competition on the predicted percentiles. Competition free dominant height was used as a driving variable for the developmental phase. Competition resulted in retarded height development within a radius of about 6 m from the retained tree, while it extended up to roughly half of the dominant height of the edge stand. The height distribution without external competition was relatively symmetrical, but increasing competition resulted in a more peaked and skewed distribution. Slight differences were found between northern sunny and southern shaded stand edges, while the least retarded height occurred at the north-western edge receiving morning sunlight. Kolmogorov-Smirnov goodness-of-fit tests showed acceptable and equal fit for both data sets; 2% and 8% of the distributions did not pass the test at the alpha 0.1 level when the Weibull distribution was estimated with the observed or predicted percentiles, respectively.
  • Siipilehto, Finnish Forest Research Institute, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: jouni.siipilehto@metla.fi (email)
article id 420, category Research article
Jukka Matero. (2004). Cost-effective measures for diffuse load abatement in forestry. Silva Fennica vol. 38 no. 3 article id 420. https://doi.org/10.14214/sf.420
Keywords: buffer strips; cost effectiveness; drainage maintenance; nutrient leaching
Abstract | View details | Full text in PDF | Author Info
This paper theoretically and empirically analyzes the design of cost-effective diffuse load abatement in forestry. Harvesting with related forest regeneration and drainage maintenance increases nutrient leaching, while riparian buffer strips and adjustments in drainage maintenance technology can be used to prevent this leaching. By utilizing a two-period model it is shown that cost-efficiency requires the establishment of a buffer strip system and a reduction in both current harvesting, and in drainage maintenance – if practized – relative to the private optimum to reflect their effects on water pollution. A simulation analysis was conducted to assess the magnitudes of the decision variables of the theoretical model, as well as to evaluate alternative technologies for the implementation and use of buffer strips and for the adjustment of drainage maintenance. The results for a representative forest holding in the southern half of Finland show that it is possible to considerably reduce total phosphorus leaching with minor cost.
  • Matero, University of Joensuu, Faculty of Forestry, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: jukka.matero@joensuu.fi (email)
article id 566, category Research article
Philip J. Burton. (2002). Effects of clearcut edges on trees in the sub-boreal spruce zone of Northwest-Central British Columbia. Silva Fennica vol. 36 no. 1 article id 566. https://doi.org/10.14214/sf.566
Keywords: tree growth; windthrow; canopy influence; clearcut logging; edge effects; edge orientation; opening influence
Abstract | View details | Full text in PDF | Author Info
Clearcut-forest boundaries were evaluated for their effects on mature and regenerating trees in the northern interior of British Columbia, Canada. Two hundred and eighteen rectangular plots measuring 200 m2 each were arrayed in transects across 12 cutblock edges created 9 to 21 years earlier, with the wall of standing timber facing either north or south. The density of canopy trees on the inner edge was found to be reduced by 19% (on north-facing edges) to 46% (on south-facing edges) from average densities found in forest interiors. This reduction was primarily due to windthrow after logging, which was elevated by 27% (over interior background levels) at north-facing edges, and by 216% at south-facing edges. Of the trees situated within 10 m of south-facing cutblock edges, 11% of the Pinus contorta, 18% of the Abies lasiocarpa, and 42% of the Picea engelmannii x glauca trees have apparently collapsed, primarily those having height-to-dbh ratios greater than 71:1. As a result, irradiance in the forest understory was elevated (over interior levels) at south-facing edges to distances of approximately 65 to 70 m into the forest. Increased irradiance from adjacent cutblocks enhanced the understory growth of Picea for approximately 60 m into the inner edge of forests, 75 m for Abies. Mature Pinus trees on south-facing edges showed an unexplained 48% decrease in radial growth compared to average growth rates in forest interiors, an effect that was detectable up to 45 m into the forest. Elevated densities of conifer seedlings were evident for up to approximately 70 m into clearcuts from north-facing forest edges. Seedling growth in clearcuts was largely unaffected by shade from stand edges. Though the extent of edge effects varies considerably with the statistical techniques used to detect them, it appears that opening effects on trees can extend between 40 and 120 m into this forest type, while canopy effects reach shorter distances into clearcuts.
  • Burton, Symbios Research and Restoration, P.O. Box 3398, 3868 13th Avenue, Smithers, British Columbia, Canada V0J 2N0 E-mail: symbios@bulkley.net (email)

Category : Research note

article id 1496, category Research note
Juha Lappi, Jaana Luoranen. (2016). Using a bivariate generalized linear mixed model to analyze the effect of feeding pressure on pine weevil damage. Silva Fennica vol. 50 no. 1 article id 1496. https://doi.org/10.14214/sf.1496
Keywords: measurement error; best linear predictor; correlated random effects; log-log link
Highlights: Probability of damage of treated seedlings can be predicted from the probability of damage of control seedlings (feeding pressure).
Abstract | Full text in HTML | Full text in PDF | Author Info

The objective of the study is to derive a method by which one can analyze how the probability of damage made by pine weevils on seedlings treated with insecticides depends on the probability of damage on untreated control seedlings, called feeding pressure. Because the probabilities vary from stand to stand and from block to block, the analysis is done using a generalized linear mixed model. The dependency of probability of damage on the feeding pressure cannot be properly analyzed using observed relative frequency of damage of control seedlings as a covariate, but it can be analyzed using a bivariate model. One equation describes damage of control seedlings and another equation damage of treated seedlings. The random stand and block effects of different equations are correlated. For a given probability of stand level control seedling damage, the random stand effect for control seedlings can be computed using a link function, then random stand effects for treated seedlings can be predicted using the best linear predictor from the random effect for control seedlings. Using an inverse link the prediction can again be presented in the probability scale which is of interest to the user. Using these three steps the probability of damage of treated seedlings can be predicted from the control damage probability. The probability of damage of treated seedlings can also be predicted from the observed relative frequency of damaged control seedlings using simulation. The complementary log-log link was used for control seedlings and the log-log link for treated seedlings.

  • Lappi, Natural Resources Institute Finland (Luke), Economics and society, Juntintie 154, FI-77600 Suonenjoki, Finland E-mail: juha.lappi@luke.fi (email)
  • Luoranen, Natural Resources Institute Finland (Luke), Management and Production of Renewable Resources, Juntintie 154, FI-77600 Suonenjoki, Finland E-mail: jaana.luoranen@luke.fi
article id 1346, category Research note
Āris Jansons, Roberts Matisons, Oskars Krišāns, Baiba Džeriņa, Mārtiņš Zeps. (2015). Effect of initial fertilization on 34-year increment and wood properties of Norway spruce in Latvia. Silva Fennica vol. 50 no. 1 article id 1346. https://doi.org/10.14214/sf.1346
Keywords: Picea abies; wood density; proportion of latewood; tree-rings; high-frequency densitometry; legacy effect
Highlights: The initial fertilization increased the productivity of Picea abies increasing stem volume by 17% at the age of 34 years; The tree-ring width was affected for up to15 years; The fertilization did not affect mean tree-ring density, although the latewood density was increased.
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Initial fertilisation, when the fertilizer is supplied during the plantation, is applied to improve the competitive ability of the seedlings and hence to increase their growth and productivity; however, fertilization could also alter wood properties and timber quality. In this study, the dimensions and tree-ring parameters – width, proportion of latewood, maximum and mean density, mean earlywood and latewood density – of initially fertilized (by 14, 6 and 11 g of N, P and K per seedling, respectively) Norway spruce (Picea abies Karst.) growing in an experimental plantation in Kalsnava, Latvia (temperate climate region) were assessed. The fertilization significantly increased the dimensions of trees in long-term (ca. 17% increase of stemwood volume). The analysis of tree-ring width suggested that the duration of the effect was ca. 15 years. The maximum and latewood density were higher for the fertilized trees only in a few years. The mean and earlywood density of tree-rings were mainly similar for both treatments. Altogether, considering the one-time application of a limited amount of fertilizer, such treatment had notable and lasting effect on Norway spruce.

  • Jansons, LSRFI “Silava”, Rigas str. 111, Salaspils, Latvia, LV2169 E-mail: aris.jansons@silava.lv
  • Matisons, LSRFI “Silava”, Rigas str. 111, Salaspils, Latvia, LV2169 E-mail: robism@inbox.lv (email)
  • Krišāns, LSRFI “Silava”, Rigas str. 111, Salaspils, Latvia, LV2169 E-mail: oskars.krisans@silava.lv
  • Džeriņa, LSRFI “Silava”, Rigas str. 111, Salaspils, Latvia, LV2169 E-mail: baiba.dzerina@silava.lv
  • Zeps, LSRFI “Silava”, Rigas str. 111, Salaspils, Latvia, LV2169 E-mail: martins.zeps@silava.lv

Category : Discussion article

article id 24004, category Discussion article
Jussi Manner. (2024). Automatic work-element detection: the missing piece in developing intelligent coaching systems for cut-to-length logging machinery. Silva Fennica vol. 58 no. 1 article id 24004. https://doi.org/10.14214/sf.24004
Keywords: forwarder; harvester; work method; operator effect; assistance system; instructor; trainer
Highlights: Next-generation logging systems will crucially impact the future demand for automatic data gathering and work guidance; Artificial intelligence emerges as a gamechanger, prompting re-evaluation of traditional approaches to automatically gather data, especially for forwarders; Industry-wide, interdisciplinary discussions are vital for charting alternative future paths for automatic data gathering and work guidance.
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The productivity of cut-to-length machine operators exhibits a significant disparity, with the most productive individuals demonstrating twice the efficiency of their less productive counterparts. This discrepancy is largely attributed to variations in work methods. While supervised training has proven effective in streamlining work methods and enhancing productivity, the availability of forest-machine instructors for supervision is limited. Intelligent coaching systems (ICS) are periodically proposed to address this constraint. ICS are computer-based aids that offer machine operators real-time feedback on their work and guide them on how to rationalize their work. The successful implementation of ICS initially requires the development of systems for automatic work-element detection (AWED). Therefore, this article explores the history, current status, and technological possibilities of AWED. Additionally, key features of ICS are briefly reviewed. Lastly, a broader, interdisciplinary discussion is initiated on how to strategically allocate limited research resources. Questions surrounding the feasible ambition level for ICS and AWED are raised, prompting considerations for the next steps in research and development.


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