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Silva Fennica vol. 47 no. 1 | 2013
Category : Research article
article id 925,
category
Research article
Steen Magnussen.
(2013).
An assessment of three variance estimators for the k-nearest neighbour technique.
Silva Fennica
vol.
47
no.
1
article id 925.
https://doi.org/10.14214/sf.925
Keywords:
forest inventory;
simple random sampling;
resampling estimators;
bootstrap;
jackknife;
difference estimator;
cluster sampling
Abstract |
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A jackknife (JK), a bootstrap (BOOT), and an empirical difference estimator (EDE) of totals and variance were assessed in simulated sampling from three artificial but realistic complex multivariate populations (N = 8000 elements) organized in clusters of four elements. Intra-cluster correlations of the target variables (Y) varied from 0.03 to 0.26. Time-saving implementations of JK and BOOT are detailed. In simple random sampling (SRS), bias in totals was ≤ 0.4% for the two largest sample sizes (n = 200, 300), but slightly larger for n = 50, and 100. In cluster sampling (CLU) bias was typically 0.1% higher and more variable. The lowest overall bias was in EDE. In both SRS and CLU, JK estimates of standard error were slightly (3%) too high, while the bootstrap estimates in both SRS and CLU were too low (8%). Estimates of error suggested a trend in EDE toward an overestimation with increasing sample size. Calculated 95% confidence intervals achieved a coverage that in most cases was fairly close (± 2%) to the nominal level. For estimation of a population total the EDE estimator appears to be slightly better than the JK estimator.
-
Magnussen,
Canadian Forest Service, Natural Resources Canada, 505 West Burnside Road, Victoria BC V8Z 1M5 Canada
E-mail:
steen.magnussen@nrcan.gc.ca
article id 904,
category
Research article
Raul Fernandez-Lacruz,
Fulvio Di Fulvio,
Dan Bergström.
(2013).
Productivity and profitability of harvesting power line corridors for bioenergy.
Silva Fennica
vol.
47
no.
1
article id 904.
https://doi.org/10.14214/sf.904
Abstract |
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Trees growing under the wires and around the pylons carrying power lines (PL) represent a significant threat to the power supply because they can cause power outages and damage. The vegetation in these PL corridors is cleared motor-manually on a regular basis, which represents about 50% of the PL maintenance costs. In Sweden, PL corridors account for 140 000 ha of productive forest land, with an estimated bioenergy potential of 3 TWh/year. The aim of this study was to measure the productivity of a harvester (with an accumulating felling head) and a forwarder, performing PL corridor clearing (with the collection of whole trees for energy use) and to calculate how the cost and economic profitability is dependent on tree height, biomass removal, harvested area, forwarding distance and wood fuel price. The study also compared the economic profitability of the mechanized harvesting system with motor-manual clearing. Experimental units were inventoried along a PL corridor in central Sweden and a time study of one harvester and one forwarder (with a single operator per machine), working in those units, was carried out. The results showed that if the tree height was greater than about 6 m, the mechanized harvesting system became a more cost-efficient alternative, when compared to motor-manual clearing, but it was also found that mechanized clearing is not always the most cost-effective option. Nevertheless, mechanization of PL clearing has a huge potential for expansion, requiring further research in the combined management of the PL corridors and side areas.
-
Fernandez-Lacruz,
Department of Forest Biomaterials and Technology, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden
E-mail:
raul.fernandez@slu.se
- Di Fulvio, Department of Forest Biomaterials and Technology, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden E-mail: fulvio.di.fulvio@slu.se
- Bergström, Department of Forest Biomaterials and Technology, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden E-mail: dan.bergstrom@slu.se
article id 903,
category
Research article
Mikko Hyppönen,
Ville Hallikainen,
Juhani Niemelä,
Pasi Rautio.
(2013).
The contradictory role of understory vegetation on the success of Scots pine regeneration.
Silva Fennica
vol.
47
no.
1
article id 903.
https://doi.org/10.14214/sf.903
Keywords:
site preparation;
seedling establishment;
seedling mortality;
field- and ground-layer vegetation;
modelling approach;
initial growth;
prescribed burning
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In North-East Finland, severe problems have been encountered in the natural regeneration of Scots pine (Pinus sylvestris L.) on sites where regeneration through site preparation usually is quite successful. We hypothesized that in that area understory vegetation, especially heather (Calluna vulgaris), crowberry (Empetrum hermaphroditum), mosses and lichens, could play a key role in this pattern. We found that in general, ground- and field-layer vegetation tends to be in a negative relationship with the establishment, growth and survival of pine seedlings. Some positive relationships were also observed. Lingonberry (Vaccinium vitis-idea) tended to improve seedling height growth. Heather, instead, seemed to have a contradictory role. It was positively related to seedling establishment but negatively to seedling growth. This dual role raises further questions about the primary reasons for the regeneration problems in North-East Finland. All in all, our results suggest that conventional methods of forest regeneration in these kinds of areas are not always effective enough and additional measures are needed. These might include severe prescribed burning along with site preparation in order to decrease the impact of the dominant ground- and field-layer vegetation on the success of Scots pine regeneration.
-
Hyppönen,
Finnish Forest Research Institute, Rovaniemi Unit, P.O. Box 16, FI-96301 Rovaniemi, Finland
E-mail:
mikko.hypponen@metla.fi
- Hallikainen, Finnish Forest Research Institute, Rovaniemi Unit, P.O. Box 16, FI-96301 Rovaniemi, Finland E-mail: ville.hallikainen@metla.fi
- Niemelä, Finnish Forest Research Institute, Rovaniemi Unit, P.O. Box 16, FI-96301 Rovaniemi, Finland E-mail: jn@nn.fi
- Rautio, Finnish Forest Research Institute, Rovaniemi Unit, P.O. Box 16, FI-96301 Rovaniemi, Finland E-mail: pasi.rautio@metla.fi
article id 902,
category
Research article
Sakari Tuominen,
Reija Haapanen.
(2013).
Estimation of forest biomass by means of genetic algorithm-based optimization of airborne laser scanning and digital aerial photograph features.
Silva Fennica
vol.
47
no.
1
article id 902.
https://doi.org/10.14214/sf.902
Abstract |
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Information on forest biomass is required for several purposes, including estimation of forest bioenergy resources and forest carbon stocks. Airborne laser scanning is today considered the most accurate remote sensing method for forest inventory. The three-dimensional nature of laser scanning data enables estimation of the volumes of the tree canopies. The dimensions of the tree canopies show high correlation with the amount of forest biomass. Optical aerial photographs are often used to complement laser data, for improved distinction between tree species. The paper reports on a study testing the estimation of forest biomass variables in two study areas in Southern Finland. The biomass variables were derived on the basis of tree-level field measurements, with biomass models used for pine, spruce, and birch. The sample-plot-level biomass components were derived on the basis of tree-level data and used as reference data for airborne-laser- and aerial‑photograph-based estimation. Results were slightly better for total biomass (RMSE 22.5% and 23.6% for the two study areas) than total volume (RMSE: 23.4% and 26.1%). Species-specific estimation errors were large in general but varied between the study areas, because of differences in their forest structures.
-
Tuominen,
Finnish Forest Research Institute, P.O.Box 18, FI-01301 Vantaa, Finland
E-mail:
sakari.tuominen@metla.fi
- Haapanen, Finnish Forest Research Institute, P.O.Box 18, FI-01301 Vantaa, Finland E-mail: reija.haapanen@gmail.com
article id 901,
category
Research article
Luis A. Apiolaza,
Rosa M. Alzamora.
(2013).
Building deployment portfolios for genotypes under performance instability.
Silva Fennica
vol.
47
no.
1
article id 901.
https://doi.org/10.14214/sf.901
Keywords:
Pinus radiata;
wood quality;
breeding objectives;
clonal portfolio;
deployment portfolio;
genotype by environment interaction
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We used portfolio theory to analyze the tradeoffs between returns and performance instability of deployment units for Pinus radiata D. Don. We considered three groups of 34 trees each grown to produce appearance lumber, structural lumber, or both. Risk was based on the variability of tree returns in scenarios of changing volume, wood stiffness and presence of resin defects due to genotype by environment interaction inducing both changes of scale and differential tree response to environmental scenarios. The return of structural trees was highly variable with a mean of 3.11 NZ $/stem/year, followed by appearance-structural trees (3.48 NZ $/stem/year). In contrast, appearance trees had the lowest returns (1.99 NZ $/stem/year) and variability. The portfolio model selected structural trees in high-risk scenarios, but selection was apportioned between structural and appearance-structural trees as the risk decreased. The model selected only appearance trees for high-risk aversion. The analysis also considered silvicultural regimes, where the appearance-structural regime was selected under high variability. As risk decreased the appearance grades regime was also selected. The structural regime was rarely selected due to the variability of stiffness between trees. Using genotypes improved for stiffness could increase the expected value and reduce variability for structural purposes, making the structural regime more appealing.
-
Apiolaza,
School of Forestry, University of Canterbury, Private Bag 4800, 8042 Canterbury, New Zealand
E-mail:
luis.apiolaza@canterbury.ac.nz
- Alzamora, Instituto de Manejo Forestal, Universidad Austral, Valdivia, Chile E-mail: ralzamor@uach.cl
article id 899,
category
Research article
Franz Holzleitner,
Christian Kanzian,
Norbert Höller.
(2013).
Monitoring the chipping and transportation of wood fuels with a fleet management system.
Silva Fennica
vol.
47
no.
1
article id 899.
https://doi.org/10.14214/sf.899
Abstract |
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Controlling and organizing the complex forest-to-consumer supply chain of wood fuels is a challenging task, especially for the chipping and transport processes. Truck mounted chippers and transport trailer-trucks must be scheduled to minimize delay to be profitable. Job management within the supply chain, including machine activity based controlling, offers a new way to increase efficiency and productivity. However, detailed data are required to detect and analyze potential gaps and improve forest fuel supply. Generally, data regarding the wood fuel supply chain process are obtained from extensive time studies that are based on a specific process step. Although time studies can detect details during the production of forest fuels, they only describe certain time frames. Long-term data that are recorded during the entire year could encompass seasonal and short term effects. This study aims to monitor the forest fuel supply processes (semi-automated), specifically regarding time and fuel consumption. Large data sets were automatically and efficiently gathered with little effort by drivers and operators. Data were recorded with fleet management equipment for more than 14 months. Vehicle data, including GPS data, were logged at an interval of one minute. Data management was conducted in a pre-configured database that contained pre-defined reports and were run by the Institute of Forest Engineering, Vienna. Work step assignments were implemented with Structured Query Language (SQL)-routines by using the raw machine activities data and GPS. The chipping and transport activities of more than 240 loads were analyzed by focusing on fuel consumption, time needed and traffic. The average distance between chipping sites and plants was approximately 54 kilometers. Fuel consumption from transport reached 50 l/100 km. The chipping unit reached a productivity of 12.8 odt/PSH15 and had a fuel consumption of 58 liters per operating hour.
-
Holzleitner,
Institute of Forest Engineering, Department of Forest and Soil Sciences, University of Natural Resources and Life Sciences, Peter Jordanstrasse 82/3, 1190 Vienna, Austria
E-mail:
franz.holzleitner@boku.ac.at
- Kanzian, Institute of Forest Engineering, Department of Forest and Soil Sciences, University of Natural Resources and Life Sciences, Peter Jordanstrasse 82/3, 1190 Vienna, Austria E-mail: christian.kanzian@boku.ac.at
- Höller, Institute of Forest Engineering, Department of Forest and Soil Sciences, University of Natural Resources and Life Sciences, Peter Jordanstrasse 82/3, 1190 Vienna, Austria E-mail: norbert.hoeller@boku.ac.at
article id 894,
category
Research article
Heimo Karppinen,
Mika Korhonen.
(2013).
Do forest owners share the public’s values? An application of Schwartz’s value theory.
Silva Fennica
vol.
47
no.
1
article id 894.
https://doi.org/10.14214/sf.894
Keywords:
demographics;
family forest owners;
objectives of forest ownership;
the public;
Schwartz’s value theory
Abstract |
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The purpose of this study is to investigate the differences in value priorities between Finnish forest owners and the general public. A conclusion is drawn whether and to what extent value changes in society are reflected in forest owners’ values and objectives, and, finally, in their actual forestry behavior. In addition, the study highlights the differences in value priorities among forest owners in various demographic groups. The data set used in this study was based on a nationwide mail survey on Finnish non-industrial private forest owners conducted in 2009 and consisting of 2116 observations of forest owners. Schwartz’s value theory was a good fit for testing the value priorities of forest owners. The three most important values were benevolence, security and conformity, both among the forest owners and the public. Tradition was ranked the fourth most important value by the forest owners, but very low by the public. The forest owners ranked universalism slightly lower than the public in general. This difference was clearly greater when the female forest owners were compared to women in the whole population. The probability of a forest owner belonging to the Softies (high emphasis on universalism and benevolence) increased with age and was higher for the female owners and the owners with recreational or multiple objectives compared to the indifferent owners. The multiobjective owners and recreationists had relatively similar value profiles. The previous literature suggests that multiobjective owners are the most active forest owner group and that recreationists and indifferent owners are the most passive groups in their timber supply behavior. The relationship between values and forestry behavior thus remains ambiguous.
-
Karppinen,
Department of Forest Sciences, P.O. Box 27, FI-00014 University of Helsinki, Finland
E-mail:
heimo.karppinen@helsinki.fi
- Korhonen, Kämnerintie 7e 41, FI-00750 Helsinki, Finland E-mail: mika.korhonen@gmx.com
article id 893,
category
Research article
Juha Heiskanen,
Timo Saksa,
Jaana Luoranen.
(2013).
Soil preparation method affects outplanting success of Norway spruce container seedlings on till soils susceptible to frost heave.
Silva Fennica
vol.
47
no.
1
article id 893.
https://doi.org/10.14214/sf.893
Keywords:
Picea abies;
pine weevil;
vole;
mounding;
reforestation;
glyphosate;
plantation establishment;
soil water content
Abstract |
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Soil preparation is a common practice that precedes outplanting of Norway spruce (Picea abies (L.) Karst.) in Finland as it enhances the survival and early growth of seedlings. Mounding in particular has become more common with Norway spruce planting in recent years. However, on fine-grained soils, the postplanting performance of seedlings has been poorer than on coarser soils even with mounding. This study examined the effects of different soil preparation treatments (spot and ditch mounding with varying mound height, inverting, unprepared control with or without a herbicide) on the postplanting performance of Norway spruce container seedlings on till soil susceptible to frost heave in two outplanting forest sites in central Finland. The results indicate higher soil temperature and lower soil water content especially in the highest mounds. Mounds, however, subsided gradually during the study years. Seedling mortality was higher and the proportion of vigorous seedlings was lower in the unprepared treatments, mainly due to increased pine weevil (Hylobius abietis L.) damage. Frost heave was present mainly on ditch mounded and inverted spots. Glyphosate herbicide treatment showed no benefit compared to the untreated control in two years. Consequently, seedling damage and conditions in the planting spots were reflected in seedling growth which was enhanced in the mounded spots. However, varying mound height or thickness of mineral capping showed no clear difference in seedling growth. The results therefore suggest that ditch or spot mounding should be used on frost heave susceptible forest soils to promote plantation establishment. Inverting or having no soil preparation with or without herbicide is not recommended.
-
Heiskanen,
Finnish Forest Research Institute, Suonenjoki Unit, Juntintie 154, FI-77600, Suonenjoki, Finland
E-mail:
juha.heiskanen@metla.fi
- Saksa, Finnish Forest Research Institute, Suonenjoki Unit, Juntintie 154, FI-77600, Suonenjoki, Finland E-mail: timo.saksa@metla.fi
- Luoranen, Finnish Forest Research Institute, Suonenjoki Unit, Juntintie 154, FI-77600, Suonenjoki, Finland E-mail: jaana.luoranen@metla.fi
article id 892,
category
Research article
M. Carmen San José,
Laura V. Janeiro,
Elena Corredoira.
(2013).
Micropropagation of threatened black alder.
Silva Fennica
vol.
47
no.
1
article id 892.
https://doi.org/10.14214/sf.892
Abstract |
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Micropropagation techniques are valuable tools for propagating, conserving and restoring trees. An efficient micropropagation method involving axillary shoot proliferation of material obtained from mature European alder (Alnus glutinosa (L.) Gaertn.) trees was developed. Branch segments from trees aged 20–30 years were forced to flush, and explants derived from new shoots were cultured on Woody Plant Medium supplemented with 8.88 µM benzyladenine and 2.85µM indole-3-acetic-acid. In vitro establishment was achieved in all five genotypes evaluated. Shoot cultures were maintained by sequential subculture of explants on the same medium supplemented with 0.88–0.44 µM benzyladenine and 2.85 µM indole-3-acetic acid. Transfer to fresh medium every 3 weeks during a 9-week multiplication period and the inclusion of 2.28 µM zeatin during the last 3 weeks of culture improved the multiplication rate and shoot quality. Use of 2% glucose as the carbohydrate source produced better results than 3% sucrose for shoot proliferation. In vitro rooting of shoots was achieved with 2% glucose and 0.49 µM indole-3-butyric acid for 7 days, followed by in vitro culture on auxin-free medium for 21 days. Rooted plantlets were acclimatized to the greenhouse and were viable for reintroduction into the natural habitat.
-
San José,
Instituto de Investigaciones Agrobiológicas de Galicia (IIAG), CSIC, Apartado 122, 15080 Santiago de Compostela, Spain
E-mail:
sanjose@iiag.csic.es
- Janeiro, INLUDES, Diputación Provincial de Lugo, Ronda de la Muralla 140, 27004 Lugo, Spain E-mail: lauravj68@hotmail.com
- Corredoira, Instituto de Investigaciones Agrobiológicas de Galicia (IIAG), CSIC, Apartado 122, 15080 Santiago de Compostela, Spain E-mail: elenac@iiag.csic.es
Category : Research note
article id 897,
category
Research note
Lars Lundqvist,
Susanne Spreer,
Christer Karlsson.
(2013).
Volume production in different silvicultural systems for 85 years in a mixed Picea abies–Pinus sylvestris forest in central Sweden.
Silva Fennica
vol.
47
no.
1
article id 897.
https://doi.org/10.14214/sf.897
Keywords:
plantation;
growth and yield;
clear-cutting;
silvicultural systems;
seed trees;
selection system;
single-tree selection;
diameter limit harvest
Abstract |
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A long-term comparison of different silvicultural systems was established in 1923 in central Sweden, in an uneven-aged mixed Norway spruce–Scots pine forest (Picea abies (L.) Karst. – Pinus sylvestris L.) with about 85% spruce and 15% pine. The five treatments consisted of two examples of even-aged management 1) clear-cutting followed by planting, and 2) seed tree regeneration, one uneven-aged management 3) selection system, one exploiting treatment 4) diameter limit cut, and 5) one untreated control plot. Each treatment plot was 1 ha, 100 m × 100 m. The plots were measured and managed at irregular intervals, ranging from 7 to 15 years. In 2007–2008 the even-aged treatments and the diameter limit cut were repeated and a new rotation started. Mean annual volume increment during the whole observation period differed widely between the treatments, partly because of differences in species composition over time, with treatment clear-cutting followed by planting at the top, and the control at the bottom. Treatment selection system gave only about 60% of planting, but this was probably largely an effect of too small growing stock during the first roughly 50 years. When the growing stock was increased, periodic annual volume increment increased to about 80% of the mean annual volume increment in the even-aged, planted plot.
-
Lundqvist,
Deparment of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden
E-mail:
lars.lundqvist@slu.se
- Spreer, Sveaskog Förvaltnings AB, Ljusdal, Sweden E-mail: susanne.spreer@sveaskog.se
- Karlsson, Field Research Unit, Swedish University of Agricultural Sciences, Siljansfors, Sweden E-mail: christer.karlsson@slu.se
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