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Silva Fennica 1926-1997
Acta Forestalia Fennica

Articles containing the keyword 'Åland'

Category: Article

article id 7155, category Article
Bo Högnäs. (1966). Investigations on forest types and stand development in Åland in Finland. Acta Forestalia Fennica vol. 78 no. 2 article id 7155.
Keywords: Finland; volume growth; coniferous forests; vegetation analysis; forest type; Åland; Ahvenanmaa
Abstract | View details | Full text in PDF | Author Info

The purpose of this study is to clarify the forest types in pure coniferous stands in Åland in Finland, to study them in a biological light and account for the production of the stands on respective sites. The flora of the forest types in Åland has been described in an earlier study, but as the plant associations have not been described it has often been difficult to determine the correct types in field work. Sample plots were chosen in coniferous forests with maximum 20% of other species. The vegetation analysis was limited to determine composition of species, projected coverage and the frequency of species. In addition, cubic volume and growth of the growing stock was calculated for the stands.

The results of the study showed that site type and fertility correspond to each other nearly without exception only on normal moraines, if only the ground vegetation is used as a criterion for the type. The general occurense of soils of different qualities makes it necessary to determine, besides forest type, other characteristics in the stands, preferably the dominant height. The total production of coniferous forests with great probability is smaller in Åland than in mainland Finland. The results can be applied also to Åboland’s archipelago, where the milieu of the coniferous forests is similar.

The PDF includes a summary in English.

  • Högnäs, E-mail: bh@mm.unknown (email)
article id 7297, category Article
A. L. Backman. (1934). Om den Åländska skogens förhistoria. Acta Forestalia Fennica vol. 40 no. 20 article id 7297.
English title: Early history of forests in Åland, Finland.
Keywords: Pinus sylvestris; Betula; Picea abies; Finland; tree species; distribution; Alnus incana; occurrence; Åland; pollen analysis; paleobotany; Carpinus betulus
Abstract | View details | Full text in PDF | Author Info

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

The PDF includes a Finnish and German summary.

  • Backman, E-mail: ab@mm.unknown (email)
article id 7071, category Article
Alvar Palmgren. (1922). Studies on vegetation characters of coniferous forests. Acta Forestalia Fennica vol. 22 no. 2 article id 7071.
Keywords: native species; vegetation; diversity; coniferous forests; Åland Islands
Abstract | View details | Full text in PDF | Author Info

The paper deals with the ground vegetation of the barren coniferous forests of Åland Islands and seeks to describe its special vegetation characters with general features. The study is based on data collected during summers from 1918-1922 on Åland Islands.  Work presents the forest types of Åland Islands classified according Cajander (1909) with their typical species.

The Ålandian coniferous forests seem to have a low number of species. This is because they are mostly old and closed, and have been developing for a long time without human induced disturbances from outside. Some changes have occurred due to forest fires. There is very few traces of non-native species in the forests. If some are found, they have not been able to regenerate or distribute widely.   

  • Palmgren, E-mail: ap@mm.unknown (email)
article id 7070, category Article
Alvar Palmgren. (1922). About the number of species and area and the structure of vegetation. Acta Forestalia Fennica vol. 22 no. 1 article id 7070.
Keywords: vegetation; diversity; species; Åland Islands
Abstract | View details | Full text in PDF | Author Info

The article describes the Ålandian vegetation of most typical habitats with greatest detail. The primary goal of the paper is to find out which deciduous species are native in the Åland Islands and hence can be seen as indicator plants for the living conditions. In addition to determining the native species of the Åland Islands, the study seeks to determine the human influence to the vegetation systems: which species are original, which have been introduced by agricultural activities, and how has the human activity influenced the abundance of the species.

The number of species varies from 44.1% to 79% of the total number of deciduous species. There is a close relation between the size of the area available for species and the number of species found. Because of that, there is a need to consider the abundance of the species alongside their diversity when studying the formation of vegetation systems or their habitats.
  • Palmgren, E-mail: ap@mm.unknown (email)
article id 7516, category Article
Euan G. Mason, A. Graham D. Whyte. (1997). Modelling initial survival and growth of radiata pine in New Zealand. Acta Forestalia Fennica vol. 0 no. 255 article id 7516.
Keywords: Pinus radiata; New Zealand; growth modelling; young corps; radiata pine
Abstract | View details | Full text in PDF | Author Info

A sensitive framework has been developed for modelling young radiata pine (Pinus radiata D. Don) survival, its growth and size class distribution, from time of planting to age 5 or 6 years. The data and analysis refer to the Central North Island region of New Zealand. The survival function is derived from a Weibull probability density function, to reflect diminishing mortality with the passage of time in young stands. An anamorphic family of trends was used, as very little between-tree competition can be expected in young stands. An exponential height function was found to fit best the lower portion of its sigmoid form. The most appropriate basal area/ha exponential function included an allometric adjustment which resulted in compatible mean height and basal area/ha models. Each of these equations successfully represented the effects of several establishment practices by making coefficients linear functions of site factors, management activities and their interactions. Height and diameter distribution modelling techniques that ensured compatibility with stand values were employed to represent the effects of management practices on crop variation. Model parameters for this research were estimated using data from site preparation experiments in the region and were tested with some independent data sets.

  • Mason, E-mail: em@mm.unknown (email)
  • Whyte, E-mail: aw@mm.unknown
article id 7608, category Article
Peitsa Mikola. (1969). Comparative observations on the nursery technique in different parts of the world. Acta Forestalia Fennica vol. 0 no. 98 article id 7608.
Keywords: Finland; New Zealand; substrate; forest nurseries; nurseries; methods; Africa; potted seedlings; greenhouses; Mediterranean countries; Australia; Latin America
Abstract | View details | Full text in PDF | Author Info

This paper is a report of the authors visits to over 80 forestry nurseries in 20 countries mostly in the tropics or subtropics. The article aim is to describe the methods used in the various countries and compares them to the conventional methods of cool and temperate countries. The article introduces nurseries of Africa south of the Sahara, Mediterranean area, Australian and New Zealand and Latin America.

A complete revolution has taken place in the Finnish nursery practice, which used to raise the seedlings in natural field soil in open-air nurseries. The seedlings were usually transplanted into transplant beds at the age of two years. Now the use of plastic greenhouses of light construction and an artificial soil substrate (fertilized peat) are essential. The new technique has some similarities to the practises of the tropical and subtropical nurseries. In Finland cultivation in greenhouses has hastened the development of the seedlings and shortened the nursery rotation from four to two years, and provided better control of watering and fertilization.

Peat beds in greenhouses are used also in Swaziland. The advantage of peat is that it is free of weed seeds, which eliminates weeding. Peat substrate gives also better yield of seedlings, which decreases the need of seeds, which is important in Finland. Another technique common with tropical silviculture is the production of potted seedlings, which are easy to handle and transport. In tropics, peat pots (jiffy pots) have made it possible to grow plantable seedlings in one season without transplanting. The present Finnish technique means a decreased degree of mechanization compared to the conventional technique of modern European and American nurseries.

  • Mikola, E-mail: pm@mm.unknown (email)

Category: Research article

article id 212, category Research article
Sandhya Samarasinghe. (2009). Exploration of fracture dynamics properties and predicting fracture toughness of individual wood beams using neural networks. Silva Fennica vol. 43 no. 2 article id 212.
Keywords: Pinus radiata; wood properties; cracks; initiation; New Zealand; peak stress; speed; video imaging
Abstract | View details | Full text in PDF | Author Info
In this study, the time to crack initiation (Tinit), duration of crack propagation (Tfrac), crack initiation stress, peak stress as well as crack speed and fracture toughness were investigated for three Rates of Loading (ROL) and four sizes of notched wood beams using high-speed video imaging and neural networks. Tinit was consistent for all volumes and the average Tinit was nonlinearly related to volume and ROL. For the smallest ROL, there was a distinct volume effect on Tinit and the effect was negligble at the largest ROL. However, the stress at crack initiation was not consistent. Contrasting these, Tfrac for all volumes appeared to be highly variable but the peak stress carried prior to catastrophic failure was consistent. The crack propagation was a wave phenomenon with positive and negative (crack closure) speeds that varied with the ROL. As accurate estimation of crack initiation load (or stress) and its relationship to peak load (or stress) is important for determining fracture toughness, Artificial Neural Networks (ANN) models were developed for predicting them from volume, Young’s modulus, face and grain angles, density, moisture content and ROL. Models for crack initiation load and peak load showed much higher predictive power than those for the stresses with correlation coefficients of 0.85 and 0.97, respectively, between the actual and predicted loads. Neural networks were also developed for predicting fracture toughness of individual wood specimens and the best model produced a statistically significant correlation of 0.813 between the predicted and actual fracture toughness on a validation dataset. The inputs captured 62% of variability of fracture toughness. Volume and Young’s modulus were the top two contributing variables with others providing lesser contributions.
  • Samarasinghe, Centre for Advanced Computational Solutions (C-fACS), Lincoln University, Canterbury, New Zealand E-mail: (email)
article id 309, category Research article
Sandhya Samarasinghe, Don Kulasiri, Tristan Jamieson. (2007). Neural networks for predicting fracture toughness of individual wood samples. Silva Fennica vol. 41 no. 1 article id 309.
Keywords: Pinus radiata; New Zealand; video imaging; strain energy release rate; Neural Networks; fracture toughness
Abstract | View details | Full text in PDF | Author Info
Strain energy release rate (GIc) of Pinus radiata in the TL opening mode was determined using the compliance crack length relationship. A total of 123 specimens consisting of four sizes of specimen with each size having four different crack lengths were tested. For each specimen, grain and ring angles, density and moisture content were measured. Video imaging, was used to measure crack length during propagation. Since cracks extended in stages, full compliance-crack length relationship was developed for each specimen based on their initial and subsequent crack lengths. No significant differences in GIc, between initial and subsequent crack lengths were found for the smaller specimens by paired sample t-tests, but differences were significant for the largest specimen size. The Average fracture toughness was calculated from GIc and it was 215 kPa.m0.5. Three artificial neural networks were developed to predict the: 1) force required to propagate a crack, 2) crack extension, and 3) fracture toughness of an individual specimen. Each was successful, producing respective R2 of 0.870, 0.865, and 0.621 on validation data. A sensitivity analysis of the networks revealed that the crack length was the most influential with 21% contribution followed by grain angle with 14% contribution for predicting the applied force. This was followed by volume and physical properties. For predicting the crack extension, density had the greatest contribution (20%) followed by previous crack length and force contributing 16% equally. Fracture toughness was dominated by the dimensional parameters of the specimen contributing (42%) followed by anisotropy and physical properties.
  • Samarasinghe, Centre for Advanced Computational Solutions (C-fACS), Lincoln University, New Zealand E-mail: (email)
  • Kulasiri, Centre for Advanced Computational Solutions (C-fACS), Lincoln University, New Zealand E-mail:
  • Jamieson, Centre for Advanced Computational Solutions (C-fACS), Lincoln University, New Zealand E-mail:

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