Current issue: 58(5)
Articles containing the keyword 'harvennus'
Category : Article
The area of stands studied by line plot survey was 594 ha. On the basis of the length of the inventory line the estimated proportion of harvesting strips was 14% and that of ditch openings 6% of the area. The calculated strip road spacing was 29 m. The option of the minimum diameter made it difficult to use the number of stems as criterion for thinning intensity. Thinning intensity evaluated according to the basal area had been stronger than recommended with low values of dominant height and milder with high values. The estimated removal according to stumps was 38 m3/ha on the average between the strips. The real removal has, however, been larger than that, as the strip road openings are made in connection with the first thinning.
The PDF includes an abstract in English.
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Rantonen,
E-mail:
hr@mm.unknown
- Päivänen, E-mail: jp@mm.unknown
Thinning models are generally based on the density of the stand measured by the average basal area per hectare, for instance. These models are handicapped by the uneven structure of the stands. In uneven stands the averages are inadequate indicators for the need and amount of thinnings.
Small relascope plots were tested in the measurement of the spatial distribution of trees and in the determination of the need and amount of thinnings. The thinning quantity was determined as the difference between the actual distribution of the relascope plots into basal area classes and the ideal distribution after thinning. Sequential sampling was used in the derivation of the decision equations. A respective BASIC-program for a programmable pocket calculator is given.
The PDF includes a summary in English.
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Kilkki,
E-mail:
pk@mm.unknown
- Pohjola, E-mail: tp@mm.unknown
- Pohtila, E-mail: ep@mm.unknown
Using literature and a simulator experiment, an ordinary processor and a grapple loader processor were compared in conditions corresponding to thinning later than the first commercial thinning. Visual bucking only was employed in the simulator experiment. The strip road spacing was 30 m and there was no preliminary skidding of the trees. The simulator experiment confirmed the view reached in the literature that work productivity of the grappler loader processor is 20–40 % greater than that of an ordinary processor provided that the stem size is under 0.2–0.4 m3.
The PDF includes a summary in English.
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Harstela,
E-mail:
ph@mm.unknown
- Maukkonen, E-mail: am@mm.unknown
In the first part of the study the hindrance of the remaining trees when felling trees by machines working from the strip road in selective thinning was studied on the basis of the literature. In the second part there was geometrically studied the need of schematic thinning in some type stands when bundles are pre-skidded straight-lined to the strip road. In average only 0-1 trees per pre-skidding trail needs to be removed. It was concluded that trees removed from the pre-skidding trail do not significantly increase the need of schematic thinning. Remaining trees do not limit the length of machine booms if the pre-skidding trails are planned during the felling.
The PDF includes a summary in English.
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Harstela,
E-mail:
ph@mm.unknown
A theoretical nomogram was made for estimating the costs of fully mechanized thinning and the driving speed of the machine. Based on this nomogram and the previous studies three harvesting methods were compared; systematic fully mechanized harvesting, selective fully mechanized harvesting, and manual felling combined with whole-tree chipping.
The third method was cheaper than the fully mechanized methods in a pole-stage stand. The choice of the most advantageous chipping station depended on conditions, but the smaller tree size and possibly the reduced damage on the remaining stand favour chipping on the strip road rather than chipping on the intermediate landing or at the mill.
Mechanized systematic thinning was the cheapest method for harvesting in the sapling stand. The required driving speed were so low that ergonomic factors should not hinder its use. Factors related to the future production of the stand do, however, limit its use. Mechanized selective thinning does not seem to be an economic method for harvesting in a sapling or pole-stage stand.
The PDF includes a summary in English.
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Harstela,
E-mail:
ph@mm.unknown
- Tervo, E-mail: lt@mm.unknown
During the next decade there will be a marked increase in the allowable cut in drained peatlands. At the same time, the mechanization in logging proceeds, and in short-distance haulage the use of forwarders will increase. This study, based on literature and some observations, deals with logging conditions in drained peatlands with special reference to the suitability of heavy logging machines for use in such terrain. In addition, soil frost and the bearing capacity of the frozen peat soil were studied.
Freezing of the soil in a drained peatland area depends prevailingly on the weather conditions during early winter. The factors influencing soil freezing of a drained peatland are completely different from those regulating the freezing of natural peat soils. The frost penetrates in general deeper in the drained than virgin peatland. The topmost peat layer does not, however, freeze uniformly. Generally speaking, the bearing capacity of a drained peat soil is lower than that of undrained peat due to lower water content.
It is concluded that heavy logging machines are probably not fitted for use in drained areas on peatland even if the average soil frost values recorded would suggest it. Moreover, because of their extremely superficial root systems, peatland forests are exposed to damages by heavy machines in thinning operations.
The PDF includes a summary in English.
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Hannelius,
E-mail:
sh@mm.unknown
The paper describes the results obtained from an investigation into the effect of thinning of different intensity and fertilization on the depth and water equivalent of the snow cover as well as on the depth of the soil frost in a young Scots pine (Pinus sylvestris L.) stand growing on drained peatland in Central Finland. Thinnings and fertilization was carried out in 1968, and the snow cover was followed in the winters 1970/71 and 1971/72.
Only extremely heavy thinnings (60% of the volume) seemed to increase the depth and water equivalent of the snow cover. The indirect effect of fertilization on the snow cover was insignificant. In the clear-cut sample plot of the study, soil frost was either not found at all or the depths of the frozen soil layer was smaller than in the other plots. When deciding the silvicultural measures to be taken in the case of tree stands growing on drained peatlands, there seems to be reason to avoid radical thinnings. Otherwise, the favourable influence of the trees on a site on its water relationships will be diminished.
The PDF includes a summary in English.
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Päivänen,
E-mail:
jp@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.
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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
The Forest Research Institute of Finland has established permanent sample plots to survey the effect of thinnings on the stands. This study compares the development of tended and natural Scots pine (Pinus sylvestris L.) stands growing on three different forest types: Oxalis-Myrtillus, Vaccinium and Calluna site type. The effect of heavy thinning from below (Oxalis-Myrtillus and Vaccinium site types) and increment felling (Calluna site type) was assessed by dividing the trees of the stands in tree classification classes according to their crown storey and defects.
The results show that thinning from below and increment thinning increase the proportion of trees in the 1st crown storey, which is already large in the natural stands. Also the diameter distribution is more even and the mean diameter higher after the thinnings.
In Scots pine stands in natural state, volume increment per stem is highest in the 1st crown storey and diminishes strongly towards the lower crown storeys. Thinnings increased the increment. The study indicates that many of the objectives of the intermediate cuttings, including promoting the growth of the best trees and improving the quality of the stand, have in general been achieved. Consequently, the thinnings give means to achieve the most valuable yield in the stand.
The article includes a summary in English.
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Nyyssönen,
E-mail:
an@mm.unknown
Silva Fennica issue 52 includes presentations held in professional development courses, arranged for foresters working in public administration in 1938. The presentations focus on practical issues in forest management and administration, especially in regional level. The education was arranged by Forest Service.
This presentation describes different types of fellings in Norway spruce (Picea abies (L.) H. Karst.) forests in different forest site types. The use of thinning from below and above, clear cutting of Norway spruce stands, and thinning of mixed forests with birch (Betula sp.) are discussed.
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Tertti,
E-mail:
mt@mm.unknown
Silva Fennica issue 46 includes presentations held in professional development courses, arranged for foresters working in public administration in 1937. The presentations focus on practical issues in forest management and administration, especially in regional level. The education was arranged by Forest Service.
This presentation describes principles of thinning of forest stands.
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Heikinheimo,
E-mail:
oh@mm.unknown
Category : Article
The present investigation revealed that the influence of a forest cover on the water economy of the soil is very great in Finland. Cutting of the forest gave cause to a rise of the ground water table, which, when clear-cutting is in question, reached a magnitude of 20–40 cm. The water supplies of the soil increased 40–60 mm. In the winter, too, the ground water remaind at a lower level in the forest than in opening, however, the difference is rather small. Thinnings had same kind of effect as clear-cuttings, but the influence of even heavy thinnings was still relatively small.
The water supplies of the soil after felling decreased mainly due to the decrease in the interception in the canopy. When the water table is at the same level in the forest and in opening, evapotranspiration might be greater in the forest than in openings. However, when the water level is during the growing season considerably lower in the forest than in an opening, the evapotranspiration is strongly decreased in the forest, which means that more water is evaporated and transpirated from the opening than from the forest. Because the water table is at a higher level in the opening than in the forest, runoff from clear-cut areas has exceeded that from the forest. This means that the influence of felling on the water economy of the soil is actually even greater than indicated in this work.
The results mean that the influence of the forest cover makes up that of drainage. This affects the need for maintenance of ditches. On the other hand, the final cutting will rise the ground water strongly.
The PDF includes a summary in English.
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Heikurainen,
E-mail:
lh@mm.unknown
Permanent sample plots are considered to be the most reliable basis for investigations into structure and development of stands. Such sample plots, established since 1924 in Finland, have been used to study thinnings of varying intensity. These studies are yet too short to give comprehensive conclusions. It is also possible to base the studies on sample plots measured in managed forests and gain in this way information suitable for practical purposes. In this investigation development of stands treated by two different methods, repeated thinnings and repeated selection cutting were studied in pure, even-aged Scots pine (Pinus sylvestris L.) stands in Southern Finland, on three forest types.
The results show that volume increment level of naturally normal stands seem to have been reached easily by stands treated with repeated thinnings. With advancing age, the growing stock of thinned stands fall short from the natural stands. As thinnings have removed primarily the poorest trees, the increment is distributed over trees of a larger size more in thinned than in naturally normal stands.
When intensive cuttings have resulted in a relatively small growing stock, the decrease in volume increment leads to considerable decrease in volume. The size of the tree has no essential effect – within certain limits - on the volume increment of the stand, if the volume removed is similar. However, every intermediate thinning removing largest-sized trees may result in the prolonged rotation. Since the volume increment of an older stand is much smaller than earlier, intermediate thinnings removing largest-sized trees should be avoided if the aim is the greatest volume yield. The growing stock of middle-aged or older stands untreated or treated with slight cuttings only can as a rule be considerably reduced without volume increment declining.
The PDF includes a summary in English.
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Nyyssönen,
E-mail:
an@mm.unknown
The growth of a tree is influenced by inherited properties and external circumstances, including climate, soil, the position of the tree in the stand, and the position of the wood in the stem. The tree species have optimum climate and optimum conditions. The aim of this study was to determine if the summerwood content of the wood of Scots pine (Pinus sylvestris L.) is dependent on the rate of growth of the tree. Comparing the position of the sample trees in the stand, it seems that the position of the tree and the size of its crown influences strongly the quality of the wood. In a dense stand the summerwood content was higher in the trees that had small crowns. Thinning of the stand decreased the difference in summerwood content of the trees.
The PDF includes a summary in English.
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Jalava,
E-mail:
mj@mm.unknown
Doctor Lauri Ilvessalo modified tree classification developed by professor Gunnar Schotte to develop a tree classification and thinning system that suited Finnish conditions. His system was first applied when the Finnish Forest Research Institute began thinning experiments in a large scale in 1924. The system distinguishes four crown storeys: the predominating crown storey, dominated crown storey, emergent trees and undergrowth. Into the predominating storeys belong dominant trees and co-dominant trees, and into the dominated storeys the intermediate and ground trees. The trees in all the storeys can be divided in to normal trees with well-formed crown and stem, trees with defectively developed crown, trees with defective stem, and injured and diseased trees. The article describes different thinning methods (cleaning thinning, selective thinning from below, selective thinning from above, increment felling, freeing felling) using the tree-classification.
The volume 34 of Acta Forestalia Fennica is a jubileum publication of professor Aimo Kaarlo Cajander. The PDF includes a summary in English.
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Ilvessalo,
E-mail:
li@mm.unknown
This study is concerned with silvicultural selection from above. The material consists of 18 Scots pine (Pinus sylvestris L.) sample plots in the southern half of Finland in experimental forests. The method is motivated by the great difference between the stumpage prices of saw timber and pulpwood. The method suggested includes the removal of individuals belonging to the predominating canopy, to achieve high levels of income from the stand at an early stage. The method is applied at when the growing stock is attaining saw-timber size. Before that the stand is treated with thinnings from below. It is supposed that the volume of growing stock is maintained at a level as high as that in below-thinned stands, and that rotation is of normal length.
On the average, the increment in basal area, as well as volume increment, is greater in stands selectively cut from above than in those treated with low thinnings of the same degree. Initially, selection from above seems to exert a negative effect upon the development of dominant height; later, the dominant height reassumes the same rate of increment as in the below-thinned stands. Selection from above also means an increase in saw-timber production, although it involves a reduction in the mean size of saw timber. The investigation includes growth and yield tables for pine stands treated with silvicultural selection from above.
The results of the investigation prove that silvicultural selection from above is at least as profitable as low thinning. This provides freedom for stand treatment, and contributes to the application of a method most suitable for the owner in each individual case. It is further stressed that the maintenance of a high wood capital in the stand is far more important than the method of thinning applied.
The PDF includes a summary in English.
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Vuokila,
E-mail:
yv@mm.unknown
