=Paper=
{{Paper
|id=Vol-2030/HAICTA_2017_paper68
|storemode=property
|title=Willows in Czech Lowlands: Variability of Density and Shrinkage
|pdfUrl=https://ceur-ws.org/Vol-2030/HAICTA_2017_paper68.pdf
|volume=Vol-2030
|authors=Vladimir Gryc,Kyriaki Giagli,Marek Fajstavr,Hanuš Vavrčík
|dblpUrl=https://dblp.org/rec/conf/haicta/GrycGFV17
}}
==Willows in Czech Lowlands: Variability of Density and Shrinkage==
https://ceur-ws.org/Vol-2030/HAICTA_2017_paper68.pdf
Willows in Czech lowlands: variability of density and
shrinkage
Vladimír Gryc1, Kyriaki Giagli1, Marek Fajstavr1, Hanuš Vavrčík1
1
Department of Wood Science, Faculty of Forestry and Wood Technology, Mendel University
in Brno, Czech Republic, e-mail: gryc@mendelu.cz
Abstract. The objective of the present study was to determine the variability
of tree-ring width, wood density and shrinkage of white willow (Salix alba L.)
growing in the lowland forest of South Moravia, Czech Republic. Six young
trees were selected from three plots (18 trees in total). Sample logs were taken
at breast height (1.3 m from the ground). All examined parameters i.e., average
tree-ring width, wood density and shrinkage were influenced by the locality.
Moreover, the results revealed much higher variability among trees per plot
than mean values among plots. Average green and dry wood density of white
willow was 753.0 kg·m-3 and 390.8 kg·m-3, respectively. Average radial
shrinkage was 3.59 % and the average tangential shrinkage 8.26 %.
Keywords: Salix alba, tree-ring width, radial shrinkage, tangential shrinkage,
variability of wood properties.
1 Introduction
Genus Salix represents about 450 species worldwide distributed mostly in the
North hemisphere (Argus 1997). White willow (Salix alba L.) is native to Europe
and Asia (western and central). Nowadays, white willow has expanded beyond its
original area, e.g. to North America and Australia. In the Czech Republic, the species
grows in the floodplain forests in warmer regions (Úradníček et al. 2001). Willows
and willow clones are fast growing species preferred for many reasons i.e.,
environmental restoration work, biomass production for energy purposes as well as
timber for wood industry (Kuzovkina and Quigley 2005, Leclerq 1997).
Wood is an exceptional raw material owing to the fact that it is renewable, very
strong and elastic despite the low density, easily shaped, ecologically recyclable etc.
Nevertheless, wood is not homogenous and it is a highly hygroscopic material. Wood
density is a fundamental property featuring the rest of wood properties. Wood
density and shrinkage depend on the genus, the locality type, wood defects and
mainly on position in the stem. Moreover shrinkage manifests the anisotropic
character of wood through different values in the individual directions (Vavrčík and
Gryc 2012, Gryc and Horáček 2007).
Our study aimed at (I) analyzing the variability of density and shrinkage of white
willow (Salix alba L.) among different plots and (II) describing the variability of
density and shrinkage among trees in each plot.
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2 Materials and methods
The sampling material was taken from white willows growing in three plots in
South Moravia, Czech Republic. All selected plots were located floodplain forest
near Židlochovice (180 m a. s. l.). The plots 1, 2 and 3 were classified as Ulmeto-
Quercetum alluviale (Brachypodium sylvaticum), Saliceto-Alnetum and Ulmeto-
Quercetum alluviale (Aegopodium podagraria), respectively. Six healthy trees were
randomly chosen per plot (mean height 23–25 m, diameter 26–32 cm). Logs (1 m)
were cut at breast height (1.3 m from the ground) from each tree. Tree-ring widths
were measured on transversal section by using Leica S6D stereomicroscope and the
VIAS TimeTable (Vienna Institute for Archaeological Science, Vienna, Austria)
measuring system (with accuracy of 0.01 mm). Samples for density and shrinkage
(20 × 20 × 30 mm) were prepared uniformly from the entire log.
The wood density was analyzed as (I) immediately after cutting (green density)
and (II) at moisture content 0 %, when samples were measured after oven drying at
temperature 103 ± 2 ºC (dry density). The wood density was calculated as:
!
ρ= [kg·m-3] (1)
!
where ρ stands for green and/or dry wood density, m stands for weight of sample
(kg), and V stands for the volume of sample (m-3).
The total linear shrinkage in the individual anatomic directions was calculated as:
! !!!"!#
𝛼 = !"#$ [%] (2)
!!"#$
where limax stands for size of the tested sample (mm) in the particular anatomic
direction at moisture content higher than the hygroscopicity level, limin stands for size
of the sample (mm) in the particular anatomic direction at moisture content 0 %.
3 Results and discussion
2.1 Variability of tree-ring width
The selected trees showed a very similar amount of tree rings, between 17 and 19
at breast height. The tree rings were wider (10–12 mm) during the first years,
followed by a gradual decreasing of tree-ring width (2–6 mm) along the stem radius
from pith to bark (Fig. 1). The average tree-ring width calculated from all three plots
was 7.51 mm, ranging between 6.62 and 8.03 mm (Table 1). Our results on tree-ring
widths were in accordance with Sacré (1974), who reported similar values (6.6–8.6
mm) depending on the logs.
555
Table 1. Descriptive statistics of tree-ring width measured in all three plots.
Plot 1 2 3 1–3
Average (mm) 6.62 8.03 7.71 7.51
Median (mm) 6.40 7.76 7.62 7.38
Standard deviation (mm) 3.43 3.34 3.21 3.39
Minimum (mm) 1.17 2.46 0.91 0.91
Maximum (mm) 14.70 17.04 14.84 17.04
Coefficient of variation (%) 51.69 41.64 41.58 45.05
Fig. 1. Variability of tree-ring width along stem radius calculated per plot. All curves represent
the mean values of six trees.
2.1 Variability of properties – density and shrinkage
We found significant differences in both average green density and average dry
density among plots (Table 2). The differences in case of green wood density among
plots were higher (81.46 kg·m-3) than in case in dry wood density (20 kg·m-3). The
average dry wood density from all three plots was 390.8 kg·m-3 ranging from 278.6 to
631.6 kg·m-3. Kollmann and Côté (1968) reported similar average dry wood density
365 kg·m-3 ranging between 320 and 420 kg·m-3. Nevertheless, Wagenführ (2000)
stated lower dry wood density 270–330–380 kg·m-3 (minimum–average–maximum),
while Wani et al. (2014) stated that basic density in Salix alba growing in Pakistan is
influenced by locality. In our study, we noticed higher variability of dry wood
density among individual trees in each plot than in average dry wood density among
the plots (Fig. 2).
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Table 2. Green and dry density of white willow wood.
Plots 1 2 3 1–3
Average 695.0 750.1 776.5 753.0
Median 682.7 741.6 763.0 749.3
Green density
(kg·m-3)
Standard deviation 132.1 92.1 119.3 122.7
Minimum 412.0 499.7 424.2 412.0
Maximum 1044.6 1044.9 1563.0 1563.0
Coeff. of variation (%) 19.0 12.3 15.4 16.3
Average 380.3 400.3 387.7 390.8
Median 384.4 399.7 389.3 392.4
Dry density
(kg·m-3)
Standard deviation 41.3 31.4 30.7 34.3
Minimum 278.6 315.7 306.9 278.6
Maximum 631.6 513.8 461.9 631.6
Coeff. of variation (%) 10.9 7.9 7.9 8.8
Average shrinkage in the radial and tangential direction was 3.59 % and 8.26 %,
respectively, which coincided with black willow radial and tangential shrinkage i.e.,
3.3 % and 8.7 % respectively (Bowyer et al. 2007) (Fig. 2, Table 3).
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Table 3. Radial and tangential shrinkage of white willow wood.
Plots 1 2 3 1–3
Average 3.41 3.86 3.51 3.59
Radial shrinkage
Median 2.99 3.67 3.24 3.31
Standard deviation 1.45 1.59 1.35 1.47
(%)
Minimum 1.03 1.17 1.11 1.03
Maximum 7.22 9.03 10.61 10.61
Coeff. of variation (%) 42.62 41.04 38.52 40.78
Average 7.46 8.45 8.41 8.26
Tangential shrinkage
Median 7.52 8.54 8.58 8.40
Standard deviation 1.70 1.62 1.58 1.69
(%)
Minimum 2.20 3.36 1.03 2.20
Maximum 13.68 13.82 13.17 15.42
Coeff. of variation (%) 22.77 19.20 18.73 20.43
558
460460
Density, MC = 0 % (kg·m-3) 440440
420420
400400
380380
360360
340340
Lokalita
320320 1
Lokalita
2
300300 Lokalita
1 2 3 4 5 6
1010 3
Tangencial schrinkage (%)
99
88
77
66 Lokalita
1
Lokalita
2
55 1 2 3 4 5 6
Lokalita
66 3
55
Radial schrinkage (%)
44
33
Plot 1
Lokalita
1
Plot 2
Lokalita
2
22 Plot 3
Lokalita
1 2 3 4 5 6
3
1 2 3 4 5 6
Tree No.
Fig. 2. Variability of wood density and shrinkage among trees.
On the contrary, Wagenführ (2000) reported again lower values for radial and
tangential shrinkage (radial: 2.4 %, tangential: 6.3 %) in comparison with our study.
Higher variability of shrinkage was observed among individual trees within the plots.
559
4 Conclusions
Our results indicated that white willow trees growing in the Czech lowlands
produce wood of higher average density in relation with the literature, while the
radial and tangential wood shrinkage were found to be in line with previous studies.
We noticed significant differences among the plots. Nevertheless the variability of
the examined properties was high among trees growing in the same plot.
Acknowledgments. We would like to thank to Forests of the Czech Republic, state –
owned company for providing experiment materials and also to all students for their
help during laboratory work.
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