Articles containing the keyword 'defect'

The present paper presents studies on the influence of some relatively common defects of Scots pine logs in Northern Finland on both the sawing yield and on the quality of the sawn goods. The study was based on test sawing of 25 logs for each of the defects (upright limb, heart shake and various kinds of wounds and scars) at Karihaara sawmill. The yield was graded into grades used for export timber according to the system of the sawmill. The proportion of the different export grades (U/S), fifths, sixths and culls) were used as characteristics together with the ratio of raw-wood consumption expressed as cu.ft/std.

Upright limbs occurring in a piece of sawn timber was shown to lower its quality to fifth grade in 43.5%, to sixth grade in 46.8% and to the category of culls in 6.5% of all cases. Only 3.2% of the cases the piece remained in U/S-grades. The size of the upright limb was the most important factor lowering the quality and affecting the ratio of raw-wood consumption.

Heart shakes are relatively common defects in pine logs deriving from over-mature trees. The quality-decreasing influence on the sawing yield depends clearly on the length of the shake in the cross-section. The same characteristics also decreases the ratio of raw-wood consumption. In addition, twisting and star shakes are considerably more harmful than straight ones. If rot occurs in connection with shakes, the places marred by the shakes are only capable of yielding sixth-grade sawn goods or culls.

Scar encountered in logs affect the sawn yield and its quality to quite a varying degree, but these defects themselves may also vary considerably both in size and quality. The length of the scar is highly significant as a quality-decreasing factor. If, in addition, rot is encountered, the defect is of a severe nature.

The PDF includes a summary in English.

• Heiskanen, E-mail: vh@mm.unknown

The aim of the present study was to find the factors influencing the distribution of Norway spruce (Picea abies (L.) H. Karst.) logs on various grades with special stress on the effects of the grade on the value of logs. The material was obtained from ten sawmills located in Southern Finland by grading a total of 13,559 logs.

The results showed that knottiness in its different forms of appearance is the most important factor influencing the quality of spruce logs. Its significance is clearly greater in spruce than in Scots pine saw logs. Among the other defects, the most common are crooks. Even scars and decay occur to a considerable degree, but other defects seldom affect the grade. The quality of butt logs is markedly better than that of top logs. Both in butt and top logs the smallest logs in diameter are of poorer quality. However, in the largest diameter classes the quality begins again to decrease.

The difference in the quality of logs of the same grade at various sawmills is very small. The results of grading at varying times at the same sawmill show greater differences than can be observed between different sawmills. However, the logs of sawmills that procure the timber from coastal areas and islands are inferior to those which procure the timber from the mainland.

The PDF includes a summary in English.

• Heiskanen, E-mail: vh@mm.unknown

The objective of this paper was to study the influence of defects of Betula pendula Roth and Betula pubescens Ehrh. on the quality, value and quantity of veneer cut produced by rotary cutting, to prepare grading rules for veneer birch and to determine the minimum quality for veneer birch, and to assess the quality and quantity of veneer yield in rotary cutting of bolts of different grades. Data for the study was collected in 1953-1963 from six plywood factories in Finland.

The effect of knot marks, knot bumps, dry and rotten knots, sound knots, sweep and crookedness, upright limbs, heart rot, open and overgrown scars and bark peeling defects in the bolt on the quality and yield of veneer is described. Recommendations for grading rules were defined on the basis of the result. The rules include three grades, for which certain defects are allowed. In the first grade are accepted bolts, which of the veneer yield included at least 30% of veneer of grades A and B when all jointing and end-clipped sheets were taken into account. In the second grade were accepted bolts, which of the main part of the veneer yield still is surface veneer on the basis of the wood quality. Of the third-grade bolts at least one third of the veneer yield ought to be surface veneer.

The PDF includes a summary in English.

• Heiskanen, E-mail: vh@mm.unknown

In acquiring land for the population displaced by the Second World War, the forest had to be priced, according to the Land Reclamation Act of 1945, separately for land and timber. Technical defects in the growing stock were to be taken account in the form of a total reduction in the value of the stock. Generally, it was to be 5-15% of the total value. The present investigation aims at checking the reduction percentages.

When the reduction in the felling value of the growing stock caused by the defects is estimated, the reduction is defined for each timber assortment, and the total reduction is calculated from these values. The timber assortments have big variation in prices, therefore defects in the most valuable assortments can have big effect on the total value of the growing stock. According to the study, the decree implementing the Land Reclamation Act did not in some cases allow for price reductions for defects on a sufficiently small scale to correspond to real conditions.

The Acta Forestalia Fennica issue 61 was published in honour of professor Eino Saari’s 60th birthday.
The PDF includes a summary in English.

• Salo, E-mail: es@mm.unknown

The quality of birch (Betula sp.) stands in Perä-Pohjola in Northern Finland is low due to the harsh environment, unsuitable sites for the species and unsatisfactory silvicultural state. A total of 236 sample trees were felled and measured in 8 sample plots. The trees were over 80 years old.

Only third of the stand volume of birch in the stands had adequate quality for merchantable timber. This is due to birch growing often in sites unsuitable for the species, the low density of the stands, the small average size of stems, and the low amount of large sized trees. These problems may contribute to the fact that birch seem to be susceptible to decay. The trees have often grown from sprouts, which leads often to poor stem form and decay. The volume and quality of both pure and mixed birch stands was sufficient only in the most fertile sites. Also, decay was more common in poor sites.

The PDF includes a summary in German.

• Tikka, E-mail: pt@mm.unknown

The aim of the study was to find out what are the causes of damage in different parts of the trees and the frequency of different kinds of injuries. Sample plots were studied in over 80-year old forests in mineral soil sites and peatlands. All the trees over 1.5 m high were felled in the sample plots and the stem injuries were studied. The structure of the stand and the crown classes were recorded. The proportion of undamaged trees was largest in in dominant and codominant trees and increased towards the better forest site types. The typical injuries are listed for Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L). H. Karst.) and Betula sp. stands. The injuries were divided in inner and outer form defects and injuries, and defined in more detail by the part of the stem and tree species. Defects caused by decay were analyzed separately.

Healing over of injuries was faster in the better sites. Form defects and other injuries were more common in birch stands than in Scots pine and Norway spruce stands. Decay was most common in birch stands. The pine stands were the healthiest, followed by spruce stands. Fire wound were most usual in pine, butt rot for spruce, and crooks and general decay for birch.

The PDF includes a summary in German.

• Tikka, E-mail: pt@mm.unknown

Moose (Alces alces L.) browsing causes severe damage in Scots pine (Pinus sylvestris L.) seedling stands. The effects of this damage on the quality of sawlogs were studied in a long-term controlled experiment. This article reports the stem size and external quality characteristics of Scots pine stems 34 years after artificial moose browsing damage. Damaging the trees by clipping the main stem at the seedling stage reduced the diameter, height, and tree volume of the trees at the end of the experiment. The tree growth reduction was dependent on the severity of clipping. The differences between the damaged and the control trees were more obvious in diameter than in height at the time of final felling. Stem form defects and vertical branches were the most typical externally detectable defects caused by clipping. Defects in the butt logs were detected in 71–89% of the damaged trees, depending on the clipping treatment severity. The stronger the clipping treatment, the more likely the stem form was defected and the more commonly were vertical branches and crooks detected in the stems. The results indicate that both tree dimensions and stem quality suffer from moose browsing. The findings of this controlled experiment more likely underestimate than overestimate the damage in comparison to real moose browsing. Further analyses are required to assess the effects of browsing damage on the internal quality of sawlogs and subsequent economic outcomes.

• Matala, Natural Resources Institute Finland (Luke), Natural resources, Yliopistokatu 6B, FI-80101 Joensuu, Finland E-mail: juho.matala@luke.fi
• Kilpeläinen, Natural Resources Institute Finland (Luke), Bioeconomy and environment, Yliopistokatu 6B, FI-80101 Joensuu, Finland E-mail: harri.kilpelainen@luke.fi
• Heräjärvi, Natural Resources Institute Finland (Luke), Production systems, Yliopistokatu 6B, FI-80101 Joensuu, Finland E-mail: henrik.herajarvi@luke.fi
• Wall, Natural Resources Institute Finland (Luke), Research infrastructure services, Yliopistokatu 6B, FI-80101 Joensuu, Finland E-mail: tapio.wall@luke.fi
• Verkasalo, Natural Resources Institute Finland (Luke), Production systems, Yliopistokatu 6B, FI-80101 Joensuu, Finland E-mail: erkki.verkasalo@luke.fi

Pruning was performed at midsummer in two genetically homogenous and managed planted silver birch stands in southern Sweden – one aged 9 and one aged 10 years. Wood defects were analysed 10 years thereafter, using the five uppermost twigs of the stems up to a height of 30 dm. The number of trees examined at each site was around 70, of which half were pruned. The main findings were that: a) compared to unpruned trees, pruned trees produced more defect-free wood outside the knots; b) most wood defects were found inside the knots; and c) wood defects like rot and bark ingrowth were similar for pruned and unpruned trees, while discolouration was marginally higher for pruned trees inside knots but similar outside knots. Overall, the results confirm previous findings that pruned birch trees will provide butt logs with higher value than unpruned trees.

• Stener, The Forestry Research Institute of Sweden, Ekebo 2250, 268 90 Svalöv, Sweden E-mail: lars-goran.stener@skogforsk.se
• Rytter, The Forestry Research Institute of Sweden, Ekebo 2250, 268 90 Svalöv, Sweden E-mail: lars.rytter@skogforsk.se
• Jansson, The Forestry Research Institute of Sweden, Uppsala Science Park, 751 83 Uppsala, Sweden E-mail: gunnar.jansson@skogforsk.se

Mortality, stem growth and quality of lodgepole pine (Pinus contorta var. latifolia) originating from the six Swedish seed orchards and local Scots pine (Pinus sylvestris L.) were estimated in four field trials established in the Komi Republic (north-west Russia). A randomized row-plot design with 6–12 replicates of each entry was used. The tree mortality was slightly higher for Scots pine than that for lodgepole pine, except for the lodgepole pine seed sources of the southern origins with lower survival. Scots pine stem quality was better than that of lodgepole pine, but the lodgepole pine stem growth was faster except the seed source of the southernmost origin. The lodgepole pine seed sources of northern origins had better stem growth (height, diameter at breast height and volume), while the effect of latitude on the quality traits was insignificant.

• Fedorkov, Institute of Biology, Komi Science Center, Russian Academy of Sciences, 28 Kommunisticheskaya st., Syktyvkar 167982, Russia http://orcid.org/0000-0001-7800-7534 E-mail: fedorkov@ib.komisc.ru
• Gutiy, Syktyvkar Forest Institute (branch), Saint-Petersburg State Forest Technical University, 39 Lenin st., Syktyvkar 167000, Russia E-mail: lguti@mail.ru

• Kretschmer, Chair of Forest Growth, Albert-Ludwigs-University Freiburg, Tennenbacher Str. 4, 79106 Freiburg, Germany E-mail: ursula.kretschmer@iww.uni-freiburg.de
• Kirchner, VOLKE Consulting Engineers GmbH, Schätzweg 7-9, 80935 München, Germany E-mail: nadeschda.kirchner@volke.muc.de
• Morhart, Chair of Forest Growth, Albert-Ludwigs-University Freiburg, Tennenbacher Str. 4, 79106 Freiburg, Germany E-mail: christopher.morhart@iww.uni-freiburg.de
• Spiecker, Chair of Forest Growth, Albert-Ludwigs-University Freiburg, Tennenbacher Str. 4, 79106 Freiburg, Germany E-mail: instww@uni-freiburg.de

• Kilpeläinen, Finnish Forest Research Institute, Eastern Finland Research Unit, P.O. Box 68, FI-80101 Joensuu, Finland E-mail: hk@nn.fi
• Lindblad, Finnish Forest Research Institute, Eastern Finland Research Unit, P.O. Box 68, FI-80101 Joensuu, Finland E-mail: jl@nn.fi
• Heräjärvi, Finnish Forest Research Institute, Eastern Finland Research Unit, P.O. Box 68, FI-80101 Joensuu, Finland E-mail: henrik.herajarvi@metla.fi
• Verkasalo, Finnish Forest Research Institute, Eastern Finland Research Unit, P.O. Box 68, FI-80101 Joensuu, Finland E-mail: ev@nn.fi

• Thomas, USDA Forest Service, 241 Mercer Springs Road, Princeton, WV 24740, USA E-mail: edthomas@gmail.com

• Viherä-Aarnio, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: anneli.vihera-aarnio@metla.fi
• Velling, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: pv@nn.fi

• Schatz, Peltotievantie 27, FI-99440 Leppäjärvi, Finland E-mail: us@nn.fin
• Heräjärvi, Finnish Forest Research Institute, Joensuu Research Unit, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: henrik.herajarvi@metla.fi
• Kannisto, Finnish Forest Research Institute, Parkano Research Unit, Kaironiementie 54, FI-39700 Parkano, Finland E-mail: kk@nn.fi
• Rantatalo, Peltotievantie 27, FI-99440 Leppäjärvi, Finland E-mail: mr@nn.fi

The consensus on the factors affecting harvester productivity is generally widely acknowledged in the discipline. However, research results regarding the effect of forking on productivity are diverse. Some studies show that harvester productivity is halved when harvesting double stems compared to single-stem trees, while other studies indicate that forking does not necessarily decrease harvester productivity. These differences in study results can depend on what is considered forking. In our study, the forking occurred above the breast-height level. We defined codominant stems as forked trees too large to be multi-tree handled. In contrast, we defined double crowns as forked trees that could be multi-tree handled. The objective of our study was to analyse how the presence of codominant stems and/or double crowns affects harvester time consumption. The study was conducted in Sweden in 2022, involving two operators and two large harvesters. The 45-year-old Pinus contorta Douglas ex Loudon-dominated stand was clearcut during the study. We found that the presence of codominant stems doubles harvester time consumption per tree, while double crowns had only a minor impact on harvester time consumption. Additionally, total time consumption increased linearly with increasing diameter at breast height. Based on these findings, we recommend that forked trees be removed already during thinning when they can still be time-efficiently multi-tree handled. Dealing with forked trees later during the rotation cycle, when they are too large for multi-tree handling, is excessively time-consuming.

• Manner, Skogforsk, Uppsala Science Park, 751 83 Uppsala, Sweden https://orcid.org/0000-0002-4982-3855 E-mail: jussi.manner@skogforsk.se
• Lundström, Skogforsk, Uppsala Science Park, 751 83 Uppsala, Sweden E-mail: hagos.lundstrom@skogforsk.se