Current issue: 58(5)
Articles by Matti Kärkkäinen
Category : Article
A mathematical model was developed for determining the value of Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) H. Karst.) stems on the basis of sawing and pulping. The model was based on selling prices of sawn goods, pulp and other products as well as processing costs. Sawing was applied to large-dimension parts of stems and pulping to other parts and small stems. Bark and other residues were burned. The quality of pine stems was described by the distance of the lowest dead branch. In spruce only stem size affected the quality-
According to the results, the size of stem affects considerably the value of pine stems and clearly that of spruce stems. The main reason is an increase in the productivity of frame sawing as the stem size increases. In pine another factor is the higher price of sawn goods. The effect of pulp price increases as the stem size decreases. Even in large sized stems the effect of pulp was notable as the value of chips and saw dust was determined on the basis of product values in export. The competition ability of mechanical pulp was greatly affected by the price of electricity.
The PDF includes an abstract in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
A computer model was developed for predicting knottiness of wood material of Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) H. Karst.) and birch (Betula sp). The prediction included location of knots, their size and quality, i.e. if they are dead or living knots. The model suits best for tree species where branches are born at the base of shoots, in Finland such tree species is Scots pine.
The usefulness of the model was tested in the prediction of knots in wooden elements of joinery industry. According to the results, the shape of cross section affects the surface quality of elements. Especially useful is a quadratic cross section as it increases the probability to get a knotless surface.
The PDF includes an abstract in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
A model was developed in order to describe the peeling of veneer for determining value relationship for birch veneer logs and stems. The model was based on selling prices of veneer and other products as well as processing costs. The model was utilized for determining the effect of various input variables on the log value.
According to the results, the effect of tree size was important for the value of raw material. Even knottiness had an effect although only in the higher manufacturing costs of knotty veneer were taken into account. Pruning was a method to increase substantially the proportion of knotless veneer.
The PDF includes an abstract in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
There are great impact forces in mechanized harvesting and wood yard in the mills which can cause breaks in timber. The impact strength of timber in green condition was tested in temperatures of +18°C and -18°C using sawn pieces (20 x 20 x 300 mm) of Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) H. Karst.), birch (Betula pendula Roth and B. pubescens Ehrh.), grey alder (Alnus incana L.) and aspen (Populus tremula L.). In addition, unbarked naturally round sticks (length 300 mm, diameter 15 and 35 mm) of the same species were tested.
The impact strength of round sticks was 1.5–4.4 times as great as that of sawn pieces. The reasons are possibly the avoidance of cell breaks at the surface as well as growth stresses. The frozen samples were clearly weaker than the unfrozen ones. As a rule, the impact bending strength increased with increased density of the species. However, the correlation varied greatly between species. If density was kept constant, an increase in the growth ring width decreased the impact strength. The reason may lie in the fracture mechanism.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
- Pietilä, E-mail: jp@mm.unknown
- Vihola, E-mail: rv@mm.unknown
A test sawing was made of 807 Scots pine (Pinus sylvestris L.) saw logs of varying size and quality. The most important knot characteristic affecting the value of sawn goods was the diameter of the thickest dry knot. The new minimum requirements for pine logs were proposed on the basis of top diameter of the log and the diameter of the thickest dry and living knot.
The PDF includes a summary in English
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Kärkkäinen,
E-mail:
mk@mm.unknown
- Halinen, E-mail: mh@mm.unknown
The aim of this literature review was to compare Finnish Norway spruce (Picea abies (L.) H. Karst.) sawn goods to Central European spruce sawn goods which contain fir in some amount. However, it was found that no statistically valid comparisons have been made. Therefore, conclusions have been based mainly on the relationship between various properties and growth rate. According to this analysis, most properties of Finnish spruce are better, although small in practice.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
Norway spruce (Picea abies (L.) H. Karst.) boards sawn from outer layers of logs were sampled from a sawmill in Northern Finland and another in Southern Finland. Test pieces 20 mm x 20 mm x 20 mm were selected according to maximum variation in growth ring width. Volumetric and longitudinal shrinkage from a soaked to a dry condition were measured. It was found that wood density correlated positively with the volumetric shrinkage but negatively with the longitudinal shrinkage. Dry density was a better predictor than basic density. With constant density and an increase in growth ring width, there was increased shrinkage, especially in samples from Northern Finland. Besides this, when density was kept constant, the shrinkage was higher in the spruce wood from Southern Finland than from Northern Finland.
The PDF includes a summary in Finnish.
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Kärkkäinen,
E-mail:
mk@mm.unknown
- Marcus, E-mail: mm@mm.unknown
The effect of growth rate on wood basic density in even-age Norway spruce (Picea abies (L.) H. Karst.) plantations was studied on the basis of samples collected from 53 stands; 30 trees were sampled in each stand. The prediction of basic density with the help of growth rate and some other tree characteristics could be improved if the social status of the tree was taken into account. Within a stand, the smaller trees had a lower density, while taller trees had a higher density than they should have had on the basis of growth rate alone.
The PDF includes a summary in Finnish.
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Kärkkäinen,
E-mail:
mk@mm.unknown
A literature survey based on Nordic literature deals with the biology, use, harvesting and economy of birch (Betula sp.). According to the results, the easily quantified hard facts are against cultivation of birch: lower growth, poorer production of valuable assortments, lower price of pulp, higher planting costs, and higher harvesting and transport costs than for conifers. The soft facts, which may be true, are not easily measured or their importance evaluated: the possible improvement of soil, decreasing risk of insect and fungi attacks, shelter against frost etc. Due to the differences in the nature of the facts the discussion of cultivation of birch will probably continue.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
In order to evaluate the strength properties of boards made from small and large Norway spruce (Picea abies) butt logs, 15 small (top end diameter 13 cm) and 15 large (top end diameter 25 cm) logs were sampled from a sawmill in Finland. From each log two test pieces were made in order to measure the bending and compression strength, dry density and average ring width.
The boards from small logs were stronger and their density higher. When the differences between groups were analysed it was found that the strength was determined by the density and ring width. When the density was kept constant, the increase in ring width had a decreasing effect on the strength properties. Because there was a negative correlation between ring width and density, ring width alone had a great effect on the strength properties.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
- Hakala, E-mail: hh@mm.unknown
A population consisting of 450 Norway spruce (Picea abies (L.) H. Karst.) samples was gathered from northern and southern Finnish wood. The static bending strength was affected greatly by the density of the wood. However, keeping the density constant, the bending strength was higher in northern than in southern Finnish wood. The reason was the effect of the growth ring width.
The basic density was affected by the growth rate. Keeping the growth ring width constant, the basic density was over 5 kg/m3 lower in northern than in southern Finnish wood. This result supports the earlier findings on the effect of latitude.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
- Dumell, E-mail: od@mm.unknown
In forestry, a classical method of evaluating the profitability of an outlay is to calculate the internal rate of return. If there are many outlays and returns over a period, analytical determination of the internal rate is difficult and requires simulation methods. However, if there is only one outlay and one return, the computation is easy. In this paper, some formulae were developed for practical purposes. The equations also show how the return changes as the ratio between the return and the outlay changes.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
A material consisting of 21 common alder (Alnus glutinosa (L.) Gaertn.) trees from 11 stands was collected. From each stem discs were sawn by 2 m interval. Samples were taken of the discs from various distances from pith. They were macerated and the average fibre length was based on 50 observations.
The fibre length increased significantly from the pith to the disc surface. The increase was approximately similar at various heights of the tree. The tree characteristics had only minor effect. However, near the pith the increase in fibre length was higher in trees with wide growth rings than in other trees. Near the disc surface the growth rate had no effect. In typical pulpwood bolts the average length was 800–950 μm which corresponds well to the data given in the literature.
The PDF includes a summary in English.
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Haarlaa,
E-mail:
rh@mm.unknown
- Kärkkäinen, E-mail: mk@mm.unknown
Eighty Betula nana samples were collected from three swamp sites. In the butt portion of the dwarf shrub the average number of growth rings was 12 and the average diameter of the sprouts 6 mm. The basic density of wood was 457 kg/m3 and that of bark 544 kg/m3. The proportion of bark was 32–38% of weight or volume. The vessel elements and fibres were short and their diameter small. The proportion of vessels was 15%, that of fibres 70% and that of rays 15%.
The PDF includes a summary in Finnish.
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Bhat,
E-mail:
kb@mm.unknown
- Kärkkäinen, E-mail: mk@mm.unknown
The anatomical variation of a lateral root was compared with that of the stem of the same tree at breast height by concentrating on the intrelationships of certain anatomical features in Betula pendula and B. pubescens. The results showed that root wood has several essential features of stem wood, such as gelatinous fibres, growth eccentricity, scalariform perforation plates in the vessels and pith flecks. However, some of the anatomical differences are significant. The differences between the species were more pronounced in the root than in the stem anatomy.
The PDF includes a summary in Finnish.
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Bhat,
E-mail:
kb@mm.unknown
- Kärkkäinen, E-mail: mk@mm.unknown
The aim of this study was to establish from the literature the purposes and for which aspen (Populus tremula L.) and related poplar species are used and can be used. According to the literature, numerous Populus species can be utilized in the industry with success instead of light softwood species in addition to them. The main emphasis is in the growing of large-sized timber, and there is no clear trend to changing to the short-rotation forestry of poplar. However, the utilization of the good sprouting properties of Populus species will probably increase as this regeneration method is cheap.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
Ten trees of mountain birch (Betula tortuosa Ledeb, now Betula pubescens subsp. czerepanovii) with an average age of 39 years were sampled in northern Lapland in Finland. The average green density of wood was 589 kg/m3 and that of bark 941 kg/m3. The basic densities were 520 kg/m3 and 559 kg/m3, respectively. The basic density increased only little from the pith to the surface. In contrast, the number of bars in the perforation plates of the vessels increased considerably in the same direction. The average number of bars was 17.3.
The PDF includes a summary in Finnish.
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Bhat,
E-mail:
kb@mm.unknown
- Kärkkäinen, E-mail: mk@mm.unknown
Downy birch (Betula pubescens Ehrh.) trees growing on a drained peatland were cut during dormancy. The properties of the one-year old shoots produced by the stumps were measured in the autumn after one growing season. The one-year old willow shoots (a mixture of Salix phylicifolia L., S. pentandra L. and S. caprea L.) were collected from an abandoned field.
The basic density of unbarked shoots was 443 kg/m3 for birch and 346 kg/m3 for willow. The basic density of the bark was much higher than that of the wood. The effect of shoot length on the properties was small with the exception of cellular proportions. The fibre percentage increased and vessel percentage decreased with increasing shoot length.
The PDF includes a summary in Finnish.
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Bhat,
E-mail:
kb@mm.unknown
- Ferm, E-mail: af@mm.unknown
- Kärkkäinen, E-mail: mk@mm.unknown
Length variation of fibres and vessels was studied in the branches, stems and roots of Betula pendula Roth and B. pubescense Ehrh. The cells were significantly shorter in the branches and roots than in the stems. There was no significant difference in the cell length between the upper and lower radii of the branches and roots. The length increased from the pith to the surface and decreased in the branches and stems from the base onwards. In the roots the length increased in that direction. The differences between the tree species were small although the cells of B. pubescens were a little longer.
The PDF includes a summary in Finnish.
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Bhat,
E-mail:
kb@mm.unknown
- Kärkkäinen, E-mail: mk@mm.unknown
Variation of cellular proportion within the same growth rings counted from the pith of the stems and branches in four trees of Betula pendula Roth was studied. The fibre percentage decreased from breast height to the crown and then increased in the branches. The reverse trend was found in the percentage of vessels and parenchyma, although the latter varied relatively little. No statistically significant differences were found in the percentages of fibres, vessels and rays within the same growth rings counted from the pith between the stems and branches. In both the stem and the branches, the proportion of fibres increased and that of vessels and rays decreased from the pith to the surface. Even crown formed wood differed from that of stem formed.
The PDF includes a summary in Finnish.
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Bhat,
E-mail:
kb@mm.unknown
- Kärkkäinen, E-mail: mk@mm.unknown
The first Finnish paper on aspen (Populus tremula L.) was published in 1759 in Åbo (Turku). After this dissertation, numerous scientific and other articles and reports have been published. In this bibliography about 340 papers are listed. Most of the papers deal only with aspen or other species of the genus Populus. Besides these even those articles have been included which deal with other problems but contain some information on the features of poplars.
The titles are listed without any translation or classification. If an article has a summary, it is shown in the title.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
- Voipio, E-mail: rv@mm.unknown
It was concluded on the basis of the anatomical investigations of four mature trees that Betula pendula Roth can be distinguished from B. pubescens Ehrh. using the number of bars per scalariform perforation plate as an identification factor. If the average number of bars is more than 17.6, the sample is probably from B. pubescens, and if less, from B. pendula. The accuracy can be slightly improved by using the vessel frequency as another factor.
The PDF includes a summary in Finnish.
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Bhat,
E-mail:
kb@mm.unknown
- Kärkkäinen, E-mail: mk@mm.unknown
A material of 478 birch logs were measured. The horizontal diameter was on average larger than the vertical one, the difference increasing with the increasing diameter. The reason was supposed to be the effect of sweep and out-of-roundness of logs. The difference between the actual and nominal length increased with the increasing lengths, but decreased with increasing diameter.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
In this study the loose volume of 58 piles of pulpwood were measured before and after barking by rotary ring barker. The volume was 2,121 m3. A recommendation is made, based on the results of the study, concerning the barking loss from piled wood: for green Scots pine (Pinus sylvestris L.) pulpwood, 8.8% of the stacked volume; for seasoned pine pulpwood, 6.1% of the stacked volume; and 8.0% for birch (Betula sp.) pulpwood, green and seasoned. The amount of bark left on bolts was small for pine bolts, namely 0.33%, but quite large for birch bolts, 2.84% of the green weight.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
According to the available literature, the times when pulpwood limbing was made by axe and barking by hand tools, barking either had no effect on the pile density (if limbing quality was good) or increased pile density (if limbing was bad). When rotary barking machines are used, the branch stumps remain intact during barking. Therefore, if there are branch stumps in the pulpwood, barking decreases the pile density. Nowadays, when power saw limbing is a common practice in Finland, barking presumably greatly decreases the pile density, due to the fact that in power saw limbing branch stumps are numerous and high. Therefore, the method to estimate the solid volume of a pile of unbarked pulpwood are not applicable to barked pulpwood without modification.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
At three Finnish match factories 1,629 aspen logs were measured (see Kärkkäinen and Salmi 1978). When the estimation was based on the condition of the butt cross section of a log, less than half of the logs were sound without any discoloration or decay. Based on the condition of the top cross-section, the corresponding figure was a little higher than 50%. The logs with decay were bigger than those without it. There were relatively more butt logs among the logs with decay than among the totally sound logs.
The PDF includes a summary in Finnish.
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Kärkkäinen,
E-mail:
mk@mm.unknown
About 100 years old larch (Larix sibirica Lebed. And L. decidua Mill.) trees were felled and the basic density samples taken from the stump level were determined. The number of trees was 21 and number of samples 378. The maximum basic density was reached at the age of 40–60 years, as counted from the pith. The basic density decreased as the width of the growth rings increased or the amount of heartwood decreased. The average basic density of the whole disc was 543 kg/m3 in L. sibirica and 497 kg/m3 in L. decidua. The basic densities of bark were 328 kg/m3 and 286 kg/m3, respectively.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
In this study two methods of determining the basic density of total tree chips are compared. The method of Mäkelä (1977) is based on the volumes of Scots pine, Norway spruce, birch, and alder in a logging area, and the age of the trees. In the other method the basic density of total tree chips is measured by the common displacement method. The correlation was 0,730 in the material of 22 logging areas. Besides this it was found that the basic density of chips increases as the size of the chip particles increases with the exception of the smallest particles.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
The paper describes the use of printed area in some scientific series concerned with forestry. The material consisted of 8 scientific series, the total number of analysed pages being 2,942. According to the results, the use of printed area was more efficient in journals and other similar periodicals which included several scientific papers than in series published as separate issues. The main reason was the more efficient editorial make-up. The Finnish papers included less figures but more tables than foreign series. There were marked differences between series irrespective of the country of origin. The average figure area varied from 60 to 180 cm2 between series, for example. According to the observations there are good possibilities for making more efficient use of the printed area available.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
According to the literature, the mechanical strength of the green reaction wood of softwood species (compression wood) is greater than that of normal wood. Drying increases the mechanical strength but less in reaction wood than in normal wood. In particular, the tensile strength along the grain and the impact strength are lower than in normal wood. The compression strength and possibly bending strength are greater, however.
The properties of the reaction wood of hardwood species (tension wood) differ from those of softwoods. When green, all mechanical properties are weaker than those of normal wood. When dried, the tensile strength and impact strength are better and compression strength lower. There is no great difference in the bending strength.
When the higher density of reaction wood is not taken into account and there are no impact forces, the mechanical strength of reaction wood in sawn goods etc. does not differ so much from that of normal wood. The harmful effect of knots, for example, can in practice be much greater.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
- Raivonen, E-mail: mr@mm.unknown
According to the available literature, the appearance of Parana pine (Araucaria angustifolia (Bertol.) Kuntze) wood resembles that of Scots pine (Pinus sylvestris L.). The anatomy is quite different, however. There are no resin canals and fusiform rays with resin canals in Parana pine. They are abundant in Scots pine, however. The basic density of Parana pine is higher. In both species the density increases from the pith outwards, the maximum being reached at the age of 100 years. Compression wood is more common in Parana pine than in Scots pine, and this makes the longitudinal shrinkage of Parana pine greater than that of Scots pine. Otherwise the shrinkage properties do not differ. The mechanical strength is of the same magnitude with the exception of hardness, where Parana pine is superior.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
In this study the area, 8 diameters, and 16 radii were measured of 174 discs representing aspen logs in a mill. The average difference between the largest and smallest diameter was 18 mm, or 7% of the longest diameter. The difference between the largest and smallest radius was 29 mm, or 22% of the longest radius. The diameter was on the average 2.4 mm longer than the two corresponding radii.
The exact area of each disc was measured using a planimeter. In comparison, the area based on the circle formula the diameter being the arithmetic mean of largest and smallest diameters overestimated the area by 1.7%. The results also indicated that the use of random direction in the measurement of diameter overestimated the cross-sectional area on the average by 1.8%.
The study is continuation of the earlier study where the bibliography is presented. As far as the results are comparable, they support each other.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
In the study the proportion of branch samples of various diameter were studied. The branches were taken from small trees to be harvested by total tree chipping method. The material consisted of 1,056 branch samples of birch (Betula verrucosa, now B. pendula Roth, and Betula pubescens Erhr.), Norway spruce (Picea abies (L.) H. Karst.) and Scots pine (Pinus sylvestris L.) at intervals of 20 cm along each branch.
With exception of the basic density of bark, there was a relation between all the other properties which were studied and the diameter. Even when the effect of diameter was eliminated, in many cases the effect of the distance of the samples from the stem became apparent.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
The paper describes a method for the measurement of basic density of total tree chips. In the method the chips are placed in a container, which is immersed in a cylinder full of water, and the container is weighted at two levels. In the upper part of the cylinder the pressure against the air bubbles is smaller than in the lower level. In this method, the effect of air bubbles in the result can be eliminated. Besides this, due to homogenization of the material to be measured only small number of samples are needed for the estimation of the average basic density.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
In this study the width and height of 1,588 uniseriate and 454 fusiform rays were measured from tangential sections of four Scots pine (Pinus sylvestris L.) trunks. The samples represented various height levels and distances from the pith. The average width of the uniseriate rays was 19.7 μm and that of the fusiform rays, 51.9 μm. The average height of the uniseriate rays was 215.7 μm and that of the fusiform rays 406.2 μm. Due to this difference in height, it may be possible to develop an automatic system for distinguishing between uniseriate end fusiform rays on the basis of their height.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
The utilization of stump and root wood is analysed in this paper on the basis of literature from middle of 19th century to the present date. According to the information available, the utilization of pine stumps in tar production was small compared to that of peeled Scots pine stemwood in the 19th century. During the 1st and 2nd World War the utilization of stumps for tar production reached its highest levels. Other industrial utilization of stumps has been small up to the present time but now stumps are beginning to be used in the pulp industry.
The greatest amounts of stumps have been utilized by the rural population. Stumps were used as fuel. In the thirties, the yearly amount used was over 200,000 m3 (solid measure), and even in the sixties over 100,00 m3. No industrial utilization method has yet reached these levels.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
The material of this study consists of 1,080 Scots pine (Pinus sylvestris L.) saw logs measures in two saw mills in Northern Finland. The largest and the smallest top-diameter of each log was measured under bark. According to the results, the ovalness was rather small, 1 mm or 4.9% on average. On the other hand, only 14.3% of all logs showed a diameter difference smaller than 2%. The ovalness was larger than 10% in 5.8% of all logs.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
The aim of the study was to determine the extent to which the cross section of birch (Betula sp.) and aspen (Populus tremula L.) logs differ from a circle and to test some simple methods for measuring the cross-sectional area which can be used, for instance, for determining the volume of the logs. The material consisted of 420 debarked birch disks and 240 aspen disks which were representative of the logs arriving at two factories.
The convex deficit values for the material were very small, the cross-sectional area error being in general less than 1%. On the other hand, the other parameters deviated from the circular form to quite a large degree. It was also evident that the radii measured from the piths to the surface of the wood varied considerably more in the same disk, as regards length, than the diameters measured in different directions.
It was evident that the shape of the average cross-sectional area was not in general elliptical. It thus appears that any method for measuring the cross-sectional area which is based on elliptical formula is not suitable. The method which gave the best result was that in which the cross-sectional area was taken as the average of the area of the circle calculated from the smallest diameter and that calculated from the diameter passing at right angles to it. This method also appeared to be the best for disks which deviated to quite a large degree from the circular form. The suitability of this method is increased by the fact that the relative error is only slightly dependent on the size of the disk.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
In this paper the use of butt and top diameters of pulpwood bolts for volume determination is analysed. The study is based on the taper data of Scots pine (Pinus sylvestris L.) stems. According to the results, the use of the mean of butt and top diameters in the volume determination under Finnish condition causes a positive error in small stems. If the stems are so big that the butt portions of the stems can be used as saw logs, the remaining top bolts, used as pulpwood, are estimated to be smaller than they are in reality. Accordingly, there is a negative error.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
In this literature review some error possibilities in the measurement of solid volume of logs and pulpwood are discussed. Although both underestimation and overestimation can occur for various reasons it seems likely that in the stereometric measurement method the real volume is underestimated, at least when Huber’s formula is applied, and the respective middle form factors are too low. Numerous results of empirical investigations are presented in the paper, too.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
The aim of the paper was to analyse, using a computer simulation technique, the moving distance of pulpwood bolts when direct felling of trees is used and the bolts are gathered alongside the strip road. According to the results, the average moving distance of bolts depends in a complicated way on the usable part of the stem and the spacing of strip road. As a rule, the differences between moving distances of two-meter bolts weighted and unweighted by bolt volume of various trees is 0–16% when the strip road spacing is 30 m the reason being the fact that the heaviest butt bolts are often more far away from the strip road than the top bolts.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
The material consists of four Scots pine (Pinus sylvestris L.) stems from which 757 samples were taken from various heights and distances from the pith. According to the results, the number of rays and their sizes are greater at the stump level than higher up in the stem. The size increases, and the number decreases on moving from the pith outwards. However, there are differences between stems as regards the variation model. The ratio between the number of fusiform rays and that of uniseriate rays seems to be lower than anticipated earlier, about 1:40–1:50. The average proportion of ray volume varied from 5.6% to 7.3%.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
The problem considered in this paper is how to analyse the usefulness of some average volume values of stems in predicting the average time consumption of some processors. In this connection, the usual arithmetic mean, the arithmetic mean weighted with volume and the geometric mean were used. The functions describing the dependence of time consumption per tree on the volume of the tree were obtained from previous studies, as were the stand properties.
The results were obtained with the aid of computer simulation techniques and the deterministic model described above. According to the results, the usual arithmetic mean is very applicable for predicting the time consumption. The geometric mean is nearly as good, or in some cases even better. However, as a rule its computation is much more tedious than that of the arithmetic average volume for the purpose.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
The study deals with the variation in the proportion of heartwood in Norway spruce (Picea abies (L.) H. Karst.) and Scots pine (Pinus sylvestris L.) both within and between stems as examined on the basis of literature. Special attention is paid to an application, in which on the basis of the diameter of pulpwood bolts, efforts are made to predict the proportion of heartwood in the total volume of bolts. It is shown that the method, even when based on homogenous material of 564 Norway spruce and Scots pine bolts, easily leads to wrong conclusions concerning the proportion of heartwood.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
The paper deals with the concepts of time consumption and output in forest work science. When output is defined as the inverse of time consumption and vice versa, it is possible to show the important consequences in probability functions. For instance, it is not the same if the dependent variable in a regression analysis is output or time consumption. Also, the average differ depending on if they are based on the time consumption figures or on the average output.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
The material comprised 12 Norway spruces (Picea abies (L.) H. Karst.) from Central Finland, with 2,118 branches. The exact location of the branches on the stems, their diameter at the thick end, their length, and the green weight of all the branches was measured on two-metre lengths of the stem.
According to the results, the diameter of a branch can be estimated very accurately from its length. The variation of branch diameter along the stem was also very regular, although there were considerable differences from one tree to another. The greatest work requirement for trimming was in the middle and upper parts of the green crown. Branch variables per tree, such as the number and cross-section area o the branches, could be satisfactorily estimated from the volume or breast-height diameter of the stem.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
The material of 78 damaged Norway spruce (Picea abies (L.) H. Karst.) trees was gathered in Southern Finland in order to clarify the advance of decay. The harvesting which had caused the scars had been carried out 12 years earlier and at the moment of the investigation the growing stand was 110 years old. It was noticed that the variables used could explain only a few per cent of the variation of the advance of decay. It was concluded that the only important thing in practice is whether the injuries are in roots or in stems.
The PDF includes a summary in English.
-
Kärkkäinen,
E-mail:
mk@mm.unknown
The goal of this study was to develop a mathematical model for determination of the optimal winching distance in different conditions as based on harvesting costs. In the thinned forest the strip roads are parallel and the winching routes perpendicularly to them. A directed felling of trees is used so that it is easy to make loads to be winched. The stems can also be prepared to timber assortments on the stump area and gathered to loads for skidding alongside the winching routes.
After winching the timber is transported using a forwarder mowing on the strip roads. If the stems have not been bucked in the forests, they are to be prepared to timber assortments before the following transportation, because the problem of turning whole stems in a thinned forest has not yet been solved.
In the mathematical model the formation of the costs was described using 18 variables of which 15 had an effect on the optimum winching distance. Some empirical values were estimated concerning these variables, and the corresponding optimum winching distance were computed. The optimum was mainly determined by the quantity of timber harvested per unit area, the size of the winching load, the regression coefficient of the times which were depended on the winching distance.
According to the model, the deviation from optimum winching distance does not cause a very great change in the analysed total costs. When the winching distance is longer, the increase of the costs is smaller than if it is shorter than optimum. In general, the increase of the costs was so small that in practice one obviously can be satisfied with rather approximate methods in determining the suitable winching distance.
The PDF includes a summary in English.
-
Kärkkäinen,
E-mail:
mk@mm.unknown
The purpose of this study was to explain whether it is possible to affect, in practical working site conditions, by means of logging waste on the strip road, the depth of the track which is formed in terrain transportation and the injuries of the growing stand. Five 20 m long investigation areas with logging waste and five similar areas without logging waste were arranged on one strip road at Teisko logging site in Southern Finland. The logging waste layer was mainly Norway spruce and 10–15 cm thick. A KL–836 B forwarder was used. The type of soil was loam.
The logging waste affected the depth of the track only by decreasing the wear of humus layer. Even decreasing effect of logging waste on the injuries in the growing stand was minor. At Kitee working site in Eastern Finland strip roads were studied. The type of soil was thick, rather mouldered peat. The thickness of logging waste was 3–4 times greater than in Teisko, mainly spruce. A Volvo Nalle SM 460 forwarder was used. The effect of the logging waste on the depth of the tracks was clearly to be noticed. On basis of the appearance of the tracks one could assume that the difference was due to different wear of the humus, and not so much due to the quantity of logging waste that improves the carrying capacity of terrain.
In some extent logging waste was also found to affect the amount and quality of tree injuries. In practical working conditions, the importance might be small, since in the experiments an unrealistically great amount of logging waste was used.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
This investigation studies the effect of the retail price and the technical properties of preference ordering of buyers of power saw. According to the model derived, the preference ordering of power saws is due to technical properties xj. If no such restrictions in the function are supposed that could have bearing on the preferences of the buyers, there may be N ! possible combinations, when there are N power saws. If one can presume that each price corresponds with a technical level it is possible that each buyer has an optimum price of his own. The bigger the difference between the optimum and actual price, the less preferred the actual power saw is. In this case one may notice the amount of possible orderings is much less than that based on the model. Thus, the mode may be used.
In this paper some models are presented for cases when only n pieces of the population of N power saws are studied. 16 power saws of differing ages and technical levels were investigated. It was noted that many criteria of technical goodness were positively intercorrelated. The price correlated positively with every criterium used. According to the profile analysis, it was concluded that there were many development lines. For example, the idea of a light and the idea of an effective power saw.
According to the principal component analysis, it seemed obvious that there was little room for one- or two-dimensional preference ordering by the technical properties and price.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
Category : Article
The purpose of this study was to build a mathematic predictive model for the formation of injuries and to try its usability in predicting. The empirical data consisted of 24 thinning sites, which were situated mainly in forests owned by forestry companies. The timber was made by strip roads. The terrain transportation of timber was carried out by forwarders or by agricultural tractor-trailer combinations.
The model has been compiled by multiple regression analysis. The predictive model has been interpreted so that the formation of injuries is, for one part, dependent of the number of trees exposed to damages, and, on the other hand, on the factors influencing the probability of injuries, the possibility for this existing. The number of trees exposed to injuries is dependent on the density of strip roads and on the amount of standing timber left after logging. The probability of injuries is influenced by the quality of the standing timber, the type of soil and the intensity of the timber harvesting process.
The predictive model has been interpreted in similar way as the number of injured trees. The possibility of formation of injuries is mainly affected by the length of strip roads and the amount of the standing timber. The probability of injuries is influenced, for the part of the number of root injuries by the strength of the soil type, and probably also by transportation equipment. For the amount of stem injuries no valid predictive equation was found in this study.
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Kärkkäinen,
E-mail:
mk@mm.unknown
