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Articles containing the keyword 'stability'

Category : Research article

article id 10483, category Research article

Māra Kitenberga, Guntars Šņepsts, Jānis Vuguls, Didzis Elferts, Ieva Jaunslaviete, Āris Jansons. (2021). Tree- and stand-scale factors shape the probability of wind damage to birch in hemiboreal forests. Silva Fennica vol. 55 no. 2 article id 10483. https://doi.org/10.14214/sf.10483

Keywords: stem breakage; Betula pendula; snapping height; stem damage; stem fracture; tree stability

Highlights: Prior stem and root damage significantly increased the probability of birch being wind-damaged; Trees with a high slenderness ratio had a lower relative snapping height; The snapping height was significantly negatively affected by the prior stem and root damage.

Abstract | Full text in HTML | Full text in PDF | Author Info

Strong wind is the major natural disturbance in European forests, that periodically causes tremendous damages to forestry. Yet, factors that affect the probability of wind damage for birch (Betula pendula Roth and B. pubescens Ehrh.), the most common deciduous tree species in hemiboreal forests, are studied scarcely. This study aimed to assess the effects of several tree- and stand-scale variables on the probability of wind damage to birch using data from the Latvian National Forest Inventory (2004–2018), and determine individual tree characteristics that affect the height of the stem breakage. The data analysis was done using the Bayesian binary logistic generalized linear mixed-effects model and a linear mixed-effects model. The probability of wind damage significantly increased by stand age, basal area, and slenderness ratio. Trees with prior damage had a significantly higher probability (odds ratio 4.32) for wind damage. For wind-damaged trees, the snapping height was significantly decreased by an increase in the slenderness ratio (p = 0.03) and prior damage (p = 0.003). Previously damaged trees were more frequently (73%) snapped in the lowest 40% of tree height than trees without prior damage (54%). The probability of wind damage is largely set by factors related to the selection of site, species composition, and rotation. The damage probability could be decreased by management measures that lower competition within the stand with particular regard to preserving intact remaining trees during these manipulations. Factors that reduce the probability of the damage simultaneously increase the snapping height, emphasizing their relevance for mitigation of the wind damages.

Kitenberga, Latvian State Forest Research Institute ‘Silava’, Rigas Street 111, LV–2169, Salaspils, Latvia https://orcid.org/0000-0002-6192-988X E-mail: mara.kitenberga@silava.lv
Šņepsts, Latvian State Forest Research Institute ‘Silava’, Rigas Street 111, LV–2169, Salaspils, Latvia E-mail: guntars.snepsts@silava.lv
Vuguls, Latvian State Forest Research Institute ‘Silava’, Rigas Street 111, LV–2169, Salaspils, Latvia E-mail: janis.vuguls@silava.lv
Elferts, Latvian State Forest Research Institute ‘Silava’, Rigas Street 111, LV–2169, Salaspils, Latvia; Faculty of Biology, University of Latvia, Jelgavas Street 1, LV–1004, Rīga, Latvia https://orcid.org/0000-0002-9401-1231 E-mail: didzis.elferts@lu.lv
Jaunslaviete, Latvian State Forest Research Institute ‘Silava’, Rigas Street 111, LV–2169, Salaspils, Latvia E-mail: ieva.jaunslaviete@silava.lv
Jansons, Latvian State Forest Research Institute ‘Silava’, Rigas Street 111, LV–2169, Salaspils, Latvia https://orcid.org/0000-0001-7981-4346 E-mail: aris.jansons@silava.lv

article id 138, category Research article

Santiago Martín-Alcón, José Ramón González-Olabarría, Lluís Coll. (2010). Wind and snow damage in the Pyrenees pine forests: effect of stand attributes and location. Silva Fennica vol. 44 no. 3 article id 138. https://doi.org/10.14214/sf.138

Keywords: models; stand structure; conifers; Pyrenees; snow damages; stability; wind damages

Abstract | View details | Full text in PDF | Author Info

Wind and snow-induced damage have been analyzed at stand level for three pine forests in the Central-Eastern Pyrenees (Pinus nigra Arn. salzmanii, Pinus sylvestris L. and Pinus uncinata Ram.). Stand-level models have been then developed for the most affected two species, Pinus sylvestris L. and Pinus uncinata Ram., to describe damage severity. The models were based on data from national forest inventory plots. They included variables related to the spatial location and structure of the stands, being validated using a sub-set of the database (25% of the plots randomly selected). Mountain pine forests (Pinus uncinata Ram.) were the most heavily affected by wind and snow disturbances. For both mountain and Scots pine species, topographic exposure and the severity of the local storm regime had an important effect on the degree of damage. Stand’s resistance to wind and snow was found to be dependent on the combined effect of basal area and mean slenderness of the dominant trees. For a given slenderness ratio, damage increased strongly in lower-density stands, particularly in stands with basal areas below 15 m²/ha. Stand structure was particularly important to define the resistance of Scots pine stands, which presented a higher vulnerability to wind and snow under higher degree of even-agedness. The models presented in this study provide empirically-based information that can be used to implement silvicultural practices to minimize the risk of those forests to suffer wind and snow-related damages.

Martín-Alcón, Forest Technology Center of Catalonia, Solsona, Lleida, Spain E-mail: santiago.martin@ctfc.es
González-Olabarría, Forest Technology Center of Catalonia, Solsona, Lleida, Spain E-mail: jrgo@nn.es
Coll, Forest Technology Center of Catalonia, Solsona, Lleida, Spain E-mail: lc@nn.es

article id 198, category Research article

Henrik Heräjärvi. (2009). Effect of drying technology on aspen wood properties. Silva Fennica vol. 43 no. 3 article id 198. https://doi.org/10.14214/sf.198

Keywords: stability; heat treatment; modification; press drying; strength

Abstract | View details | Full text in PDF | Author Info

Heräjärvi, Metla, Joensuu Research Unit, Box 68, FI-80101 Joensuu, Finland E-mail: henrik.herajarvi@metla.fi

article id 257, category Research article

Nadir Ayrilmis. (2008). Effect of compression wood on dimensional stability of medium density fiberboard. Silva Fennica vol. 42 no. 2 article id 257. https://doi.org/10.14214/sf.257

Keywords: compression wood; linear expansion; linear contraction; thickness swelling; thickness shrinkage; medium density fiberboard; dimensional stability

Abstract | View details | Full text in PDF | Author Info

This study evaluated the effect of compression wood on dimensional stability of medium density fiberboards (MDF) manufactured from fiber furnishes of pine (Pinus nigra Arnold var. pallasiana) containing compression wood. Two panel types were manufactured from two different compression wood (CW) portion / normal wood (NW) portions in the furnish, 75/25 and 10/90, respectively. Linear and thickness variations of the panels exposed to various relative humidites at 20 °C, linear expansion/contraction and thickness swelling/shrinkage, were measured according to the procedures defined by DIN EN 318 (2005) standard test method. Panels made from fiber furnish containing 75% the CW had higher linear expansion and linear contraction values with an average value of 0.286% and 0.247% than those of panels made from fiber furnish containing 10% the CW with an average value of 0.184% and 0.152%, respectively. As for thickness swelling and thickness shrinkage properties, panels made from fiber furnish containing 75% the CW had the thickness swelling and thickness shrinkage values with an average of 5.042% and 4.402% while panels made from fiber furnish containing 10% the CW had the values with 3.621% and 2.861%, respectively. Consequently, based on the findings obtained from this study, expansion and swelling properties of the MDF panels were negatively affected by compression wood increase.

Ayrilmis, University of Istanbul, Faculty of Forestry, Department of Wood Mechanics and Technology, Bahcekoy, TR-34473 Istanbul, Turkey E-mail: nadiray@istanbul.edu.tr

article id 278, category Research article

Katri Luostarinen. (2007). The effect of annual ring orientation and drying method on deformations, casehardening and colour of silver birch (Betula pendula) boards. Silva Fennica vol. 41 no. 4 article id 278. https://doi.org/10.14214/sf.278

Keywords: wood; timber quality; dimensional stability; distortion; drying schedules; kiln drying; L*a*b* coordinates

Abstract | View details | Full text in PDF | Author Info

Deformations of timber, caused mainly by anisotropic shrinkage, can be partially directed by controlling annual ring orientation through different sawing patterns. Ring orientation also affects the movement of water from within the board to its surface, with rapidity of drying having implications for the wood colour. Here sawn silver birch (Betula pendula Roth) timber was classed into two groups according to ring orientation. Two drying methods were used. The final moisture content was lower and the colour lighter in dried boards with radial than with tangential flats, but deformations were larger in radial than in tangential boards. Both drying and ring orientation affected the final moisture content and moisture gradient of the boards. Very small differences in board sizes or shape had an effect on both colour and deformations. The results support the need for accurate sawing and for classing silver birch timber sawn into parquet billets according to ring orientation in order to optimise the drying quality.

Luostarinen, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: katri.luostarinen@joensuu.fi

article id 493, category Research article

Göran Rune. (2003). Slits in container wall improve root structure and stem straightness of outplanted Scots pine seedlings. Silva Fennica vol. 37 no. 3 article id 493. https://doi.org/10.14214/sf.493

Keywords: Pinus sylvestris; solidwall container; slitwall container; root morphology; mechanical instability; stem straightness

Abstract | View details | Full text in PDF | Author Info

Root structure and basal sweep were measured on 6-year-old Scots pine (Pinus sylvestris L.) trees at two sites with different soil fertility. Each site was planted with seedlings of identical origin after nursery cultivation in either solidwall container types with vertical ribs or in slitwall container types. Neither container design nor container volume affected tree height or stem diameter on the two sites. The transversal area of lateral roots was larger than the transversal area of bottom roots for the two container types at both sites. The proportion of bottom root transversal area to the total root transversal area was larger in the seedlings growing on the low fertility site than in those growing in the high fertility site for both container types. Seedlings cultivated in slitwall containers had a larger root area in proportion to stem diameter and had less root spiralling compared to the trees cultivated in solidwall containers. At the high fertility site, trees from the slitwall container type had straighter stem bases than seedlings grown in solidwall containers. At the low fertility site, differences in basal sweep formation were small between the container types. Reasons for this are discussed.

Rune, Dalarna University, Department of Forestry and Wood Technology, SE-776 98 Garpenberg, Sweden E-mail: gru@du.se

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