GROUPING OF CLONES OF 4-YEAR-OLD Eucalyptus spp. FOR PULP AND PAPER

Abstract

As in other countries, In Brazil, new genetic materials of Eucalyptus spp. and their hybrids are multiplied through cloning. These materials, currently in experimental trials, must undergo several stages to select the best ones for pulp and paper production. Therefore, new studies on wood quality are essential. Therefore, this study aimed to group 11 clones of Eucalyptus spp. wood, from a clonal plantation in the municipality of Palmital, São Paulo State, for the production of paper and cellulose. For this purpose, four trees of each clone of 4-year-old Eucalyptus spp. were collected. From each tree, a log of 1 m in length was taken from the base of the tree, for the study of the characterization of the basic density and cellular dimensions of the wood. The results showed that there were significant differences between clones for basic density, fiber length, vessel element length and fiber wall thickness. The Runkel ratio, wall fraction and stiffness coefficient did not show significant differences between the different genotypes. From the results obtained, we can conclude that clones can be differentiated only by basic density, fiber length, vessel element length and fiber wall thickness. The Runkel index, flexibility coefficient and wall fraction of Eucalyptus spp. were more efficient to group the clones into two groups.

Full text

Rev. Inst. Flor., v. 36: e937, 2024
http://doi.org/10.24278/rif.2024.36e937
ISSN on-line 2178-5031
______
1 Recebido para análise em 11.04.2023. Aceito para publicação em 25.04.2024. Publicado em 10.05.2024.
2 Instituto de Pesquisas Ambientais, Rua do Horto, 931, 02377-000, São Paulo, SP, Brasil.
3 Autor para correspondência: israellima@gmail.com.
GROUPING OF CLONES OF 4-YEAR-OLD Eucalyptus spp. FOR PULP AND PAPER1
AGRUPAMENTO DE CLONES DE Eucalyptus spp. AOS 4 ANOS PARA PAPEL E CELULOSE1
Patricia Gurgel VICENTIN2, Maurício RANZINI2; Osmar VILAS BÔAS 2; Eduardo Luiz LONGUI2; Israel
Luiz de LIMA2,3
ABSTRACT - As in other countries, In Brazil, new genetic materials of Eucalyptus spp. and
their hybrids are multiplied through cloning. These materials, currently in experimental trials,
must undergo several stages to select the best ones for pulp and paper production. Therefore,
new studies on wood quality are essential. Therefore, this study aimed to group 11 clones of
Eucalyptus spp. wood, from a clonal plantation in the municipality of Palmital, São Paulo State,
for the production of paper and cellulose. For this purpose, four trees of each clone of 4-year-old
Eucalyptus spp. were collected. From each tree, a log of 1 m in length was taken from the base
of the tree, for the study of the characterization of the basic density and cellular dimensions of
the wood. The results showed that there were significant differences between clones for basic
density, fiber length, vessel element length and fiber wall thickness. The Runkel ratio, wall
fraction and stiffness coefficient did not show significant differences between the different
genotypes. From the results obtained, we can conclude that clones can be differentiated only by
basic density, fiber length, vessel element length and fiber wall thickness. The Runkel index,
flexibility coefficient and wall fraction of Eucalyptus spp. were more efficient to group the clones
into two groups.
Keywords: Genetic improvement; Density; Wood anatomy; Wood quality.
RESUMO - A exemplo de outros países, no Brasil os novos materiais genéticos de espécies do
gênero Eucalyptus e seus híbridos multiplicados pelo processo de clonagem, existentes em
ensaios experimentais, ainda necessitam passar por várias etapas para a seleção dos melhores
materiais para a produção de papel e celulose. Com isso, novos estudos sobre a qualidade da
madeira são indispensáveis. Sendo assim, este estudo teve como objetivo agrupar clones de
Eucalyptus spp., provenientes de um plantio clonal da região de Palmital, estado de São Paulo,
para a produção de papel e celulose. Para tanto, quatro árvores de cada clone de Eucalyptus spp.,
com quatro anos de idade, foram coletadas. De cada arvore foram retiradas uma tora de 1 m de
comprimento da base da árvore, para o estudo da caracterização densidade básica e dimensões
celulares da madeira. Os resultados mostraram que ocorreram diferenças significativas entre os
clones, para a densidade básica, comprimento de fibras, comprimento de elemento de vaso e a
espessura da parede da fibra. O fator de Runkel, fração parede e o coeficiente de rigidez não
apresentaram diferenças significativas entre os diferentes genótipos. De acordo com os
resultados obtidos até a idade de 4 anos, podemos concluir que os clones podem ser diferenciados
apenas pela densidade básica, comprimento de fibra, comprimento de elemento de vaso e a
espessura da parede da fibra. O índice de Runkel, coeficiente de flexibilidade e fração parede
de Eucalyptus spp. foram mais eficientes para agrupar os clones em dois grupos.
Palavras-chave: Melhoramento genético; Densidade; Anatomia da madeira; Qualidade da
madeira.
1 INTRODUCTION
Brazil continues to be a world reference when it
comes to productivity of forest plantations, with a
high volume of annual wood production per area
and a short cycle. In addition to climate and soil
conditions, the sector invests years in research and
development of the best forest management
techniques, combined with genetic improvement
and sustainable practices (Indústria Brasileira de
Árvores - IBÁ, 2023).
.

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VICENTIN, P.G. et al. Selection of clones for pulp and paper
Rev. Inst. Flor., v. 36: e937, 2024
The use of cloning of Eucalyptus spp. is a
technology widely used by large companies in the
Forest Sector, today this technology can also be
used by rural producers interested in diversifying
their activities, as in other countries. Eucalyptus
plantations in 2022 occupied 7.58 million hectares,
representing 76% of the total planted area in Brazil,
concentrated mainly in the states of Minas Gerais,
São Paulo and Mato Grosso do Sul (IBÁ, 2023).
In Brazil, the new genetic materials of
Eucalyptus species and hybrids (clones or seeds)
existing in experimental trials, or in commercial
plantations, need to be tested for aptitudes for
various uses of wood (Lima and Stape, 2017).
Some of these species have adapted well to the
climate and different types of soil in Brazil, being
versatile and widely used in the industrial sector.
Initially, genetic improvement was linked to
companies in the pulp, paper, sheet metal and steel
industry and, later, it began to be used in the field of
poles and wood for structures in civil construction
(Lima et al., 2006).
The productivity of forest plantations of
Eucalyptus clones must be incorporated into wood
quality studies, to improve the understanding of the
composition and organization of the cell types that
make up the wood, as this can be a decisive factor
for these new genetic materials to be processed and
used in a rationally sustainable way (Protásio et al.,
2014).
New studies on wood quality must consider
different genetic materials, growing environments,
planting spacing, treatments and cutting ages, to
allow greater knowledge about growth and factors
that can influence the quality of wood produced and
the adjustments that can help with forest
management, processing and the most appropriate
use of wood, in order to consider the best cost-
benefit ratio (Lima et. al. 2021). Knowledge about
the behavior of clones is restricted to the bioclimatic
region for which they were developed.
Consequently, testing these materials in small
experimental plots in the municipality of Palmital,
São Paulo State has great importance to generate the
necessary knowledge for the successful
implantation of future forests using this technology.
Therefore, this study aimed to group 11 clones
of Eucalyptus spp. wood, from a clonal plantation
in the municipality of Palmital, São Paulo State, for
the production of paper and cellulose.
2 MATERIAL AND METHODS
2.1 Planting area and sampling
The material used in this research was obtained
from experimental populations of Eucalyptus clones
planted in Horto Florestal de Palmital, municipality
of Palmital, São Paulo State, coordinates 22°48′S
and 50°16′W, in elevation 400m (Figure 1 and
Table 1). The local soil is classified as LVdf,
precipitation of 1,377 mm, average temperature of
21.2°C and the climate according to Köppen is Cfa
(Alvares et al., 2013). To test wood properties,
samples from 11 clones of 4-year-old Eucalyptus
spp., four trees of each clone were collected.
Figure 1. Overview of experimental populations of Eucalyptus clones planted in the municipality of Palmital, São Paulo
State.
Figura 1. Visão geral das populações experimentais de clones de Eucalyptus plantados no município de Palmital, estado
de São Paulo.

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VICENTIN, P.G. et al. Selection of clones for pulp and paper
Rev. Inst. Flor., v. 36: e937, 2024
Table 1. Dendrometric survey of the experimental plot.
Tabela 1. Levantamento dendrométrico da parcela experimental.
Treatment
Clone
Age
(years)
DBH
(cm)
HT
(m)
CP01
C 219 H
4
14.0
20.95
CP02
433 – E. plathyphylla (var E. urophylla)
4
15.6
21.10
CP03
162 – (E. grandis 0316201)
4
14.7
20.63
CP04
154
4
14.6
20.46
CP05
CLONE 105
4
14.2
21.00
CP06
CLONE H 15
4
15.9
20.13
CP07
H 77
4
14.8
19.58
CP08
UROCAM
4
15.5
19.46
CP09
608 – E. grandis x E. resinifera
4
13.3
18.13
CP10
TC50
4
14.7
20.58
CP11
GG100
4
16.1
21.70
Before felling the trees, the north direction was
marked on each one of them. Afterwards, the first
log of 1 m in length was taken, being properly
identified and marked. Subsequently, they were
unfolded and a central plank 7 cm thick was taken
from each of the logs. From the planks, a 4 cm x 4
cm x 1 m batten was removed from the region close
to the bark from the north direction and then
samples were taken to study the wood properties.
2.2 Wood properties
The samples obtained were transformed into
specimens for the study of basic density (BD),
vessel element length (VEL), fiber length (FL),
fiber diameter (FD), fiber lumen (FL), fiber wall
thickness (FWT), Runkel ratio (RR), wall fraction
(WF) and flexibility coefficient (FC).
To obtain the basic density (BD), the hydrostatic
balance method was used according to NBR 11941
(ABNT, 2003). The 2 x 2 x 3 cm specimens
obtained were saturated in water for a period of
approximately one month, which made it possible to
obtain the saturated and immersed mass of each
sample. Subsequently, these specimens were dried
in an oven until reaching constant dry mass at 105 ±
3oC.
To determine the anatomical dimensions, other
specimens measuring 2 x 2 x 3 cm were made, from
which small fragments were removed to be
macerated according to the modified Franklin
method (Berlyn and Miksche, 1976). Measurements
were performed using a microscope equipped with
a digital camera and a computer with image analysis
software. Photographs were taken of 25 different
vessels and fibers, using the Image-Pro Plus 6.0
program to measure vessel length, fiber length,
diameter and fiber lumen, using the methodology
recommended by the IAWA (1989).
2.3 Anatomical ratios for pulp and paper
The samples obtained were transformed into
specimens for the study of basic density (BD),
vessel element length (VEL), fiber length (FL),
fiber diameter (FD), fiber lumen (FL), fiber wall
thickness (FWT), Runkel ratio (RR), wall fraction
(WF) and flexibility coefficient (FC).
After obtaining the fiber dimension values, the
fiber wall thickness (FWT), Runkel ratio (RR), wall
fraction (WF) and flexibility coefficient (FC) were
also calculated. We used equations (1-4) according
to Paula and Alves (2007):

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VICENTIN, P.G. et al. Selection of clones for pulp and paper
Rev. Inst. Flor., v. 36: e937, 2024
To calculate the wall thickness of the fibers,
equation (1) was used:
  󰇡
󰇢 Eq. 1
Where: FWT: fiber wall thickness (µm); FD:
fiber diameter (µm), and FLD: fiber lumen diameter
(µm).
To calculate the Runkel ratio, equation (2) was
used:
  󰇡
 󰇢 Eq. 2
Where: RR= Runkel ratio, FWT = fiber wall
thickness (µm), and FLD= fiber lumen diameter
(µm).
To calculate the wall fraction, equation (3) was
used:
  󰇡
 󰇢 Eq. 3
Where: WF = wall fraction (%), FWT = fiber
wall thickness (µm), and FD= fiber diameter (µm).
To calculate the flexibility coefficient, equation
(4) was used:
  󰇡
 󰇢 Eq. 4
Where: FC = flexibility coefficient (%); FLD =
fiber lumen diameter (µm), and FD= fiber diameter
(µm).
The results were assessed through analysis of
variance (ANOVA) and the Duncan test at a 5%
significance level to identify variations among
genotypes. Additionally, a clustering analysis of the
clones was conducted, employing a cluster
dendrogram. To ascertain the properties exerting the
greatest influence on clone grouping, a principal
component analysis (PCA) was performed. All
statistical analyses were executed using the R
software (R Core Team, 2019).
3 RESULTS AND DISCUSSION
The mean and standard deviation of the wood
properties evaluated are in Table 2. Table 3 serves
as a literature reference for comparing the results of
each variable in our study with those of other studies
in different species of Eucalyptus. Table 2 has all
values for 4-year-old Eucalyptus clones (Table 3),
however, has values for different Eucalyptus
species at older ages, between 6 to 11 years old.
According to the mean values and standard
deviations of each variable according to each
genotype the wood basic density values presented,
they can be classified as being from low to medium
density (Foelkel, 2009). Clone CP01 had the highest
value, while clone CP03 had the lowest, which
significantly differentiated these two genotypes
(Table 2 and Figure 2A).
The values for wood basic density were observed
by several authors in general (Table 3), we found
that the average values (0.47 g cm-3) observed for
the basic density of the clones (4-years-old) are
similar to those in the literature, however these ones
were analyzed at older ages (6 to 11 years old)
(Table 2, Table 3 and Figure 2A).
Fiber length showed a significant difference
between clones, Clones CP04 and CP06 showed the
highest values and clones CP07 and CP10 the
lowest fiber length values. In general, we found that
the mean values (928 µm) observed for the fiber
length of the clones (4-year-old) are lower than
those in the literature (Table 2, Table 3 and Figure
2B).
.

5
VICENTIN, P.G. et al. Selection of clones for pulp and paper
Rev. Inst. Flor., v. 36: e937, 2024
Table 2. Mean and standard deviation for basic density (BD), fiber length (FL), vessel element length (VEL), fiber wall
thickness (FWT), Runkel ratio (RR), flexibility coefficient (FC) and wall fraction (WF) of 4-year-old Eucalyptus spp. (11
clones).
Tabela 2. Média e desvio padrão para densidade básica (BD), comprimento da fibra (FL), comprimento do elemento de
vaso (VEL), espessura da parede da fibra (FWT), índice de Runkel (RR), coeficiente de flexibilidade (FC) e fração
parede (WF) de Eucalyptus spp. (11 clones) aos quatro anos de idade.
Treatment
BD
(g cm-3)
FL
(µm)
VEL
(µm)
FWT
(µm)
RR
FC
(%)
WF
(%)
CP01
0.54
(0.04)
951
(95.47)
562.41
(29.55)
3.76
(0.20)
0.99
(0.17)
52.15
(4.90)
47.85
(4.90)
CP02
0.44
(0.06)
975
(81.11)
602.34
(85.42)
3.81
(0.18)
0.91
(0.23)
53.85
(6.20)
46.15
(6.20)
CP03
0.42
(0.02)
969
(47.17)
546.11
(28.94)
3.75
(0.63)
0.80
(0.15)
57.14
(4.52)
42.86
(4.52)
CP04
0.43
(0.03)
1017
(126.59)
554.99
(23.03)
4.09
(0.48)
1.04
(0.33)
51.20
(7.01)
48.80
(7.01)
CP05
0.48
(0.02)
928
(76.82)
558.28
(89.27)
3.60
(0.20)
1.09
(0.20)
50.10
(4.81)
49.90
(4.81)
CP06
0.48
(0.01)
1031
(25.07)
567.98
(30.54)
3.39
(0.39)
0.93
(0.34)
54.68
(8.99)
45.32
(8.99)
CP07
0.51
(0.04)
816
(111.31)
459.23
(110.90)
4.12
(0.54)
1.19
(0.36)
49.05
(7.63)
50.95
(7.63)
CP08
0.47
(0.02)
872
(81.69)
478.55
(29.77)
3.84
(0.35)
1.15
(0.47)
50.52
(9.84)
49.48
(9.84)
CP09
0.49
(0.04)
851
(13.29)
481.62
(69.67)
3.63
(0.31)
0.86
(0.36)
56.56
(8.61)
43.44
(8.61)
CP10
0.47
(0.04)
819
(123.07)
502.60
(53.19)
3.47
(0.45)
0.83
(0.28)
57.96
(7.77)
42.04
(7.77)
CP11
0.47
(0.04)
974
(56.51)
598.89
(32.48)
3.81
(0.26)
0.77
(0.20)
59.20
(5.83)
40.80
(5.83)
Mean
0.47
(0.04)
928
(76.76)
537.55
(49.27)
3.75
(0.23)
0.96
0.14)
53.86
(3.50)
46.14
(3.50)
Values in parentheses represent the SD = standard deviation.
Os valores entre parênteses representam o DP = desvio padrão.

6
VICENTIN, P.G. et al. Selection of clones for pulp and paper
Rev. Inst. Flor., v. 36: e937, 2024
Table 3. Basic density (BD), fiber length (FL), vessel element length (VEL) in Eucalyptus spp. as a function of age, data
obtained according to the reference.
Tabela 3. Densidade básica (BD), comprimento de fibra (FL), comprimento de elemento de vaso (VEL) em Eucalyptus
spp. em função da idade, dados obtidos na literatura.
Species
Age
(years)
BD
(g cm-3)
FL
(µm)
VEL
(µm)
Reference
Eucalyptus grandis x
Eucalyptus urophylla
2
0.40
878
-
Zanuncio et al. (2018)
Eucalyptus benthamii
5
-
903
374
Baldin et al. (2017)
Eucalyptus dunnii
5
-
982
412
Baldin et al. (2017)
Eucalyptus grandis
5
-
1036
530
Baldin et al. (2017)
Eucalyptus saligna
5
-
1078
503
Baldin et al. (2017)
Eucalyptus grandis x
Eucalyptus urophylla
6
0.46
-
-
Talgatti et al. (2018)
Eucalytus benthamii
6
0.48
937
-
Bonfatti Júnior et al. (2023)
Eucalytus dunnii
6
0.49
960
-
Bonfatti Júnior et al. (2023)
Eucalytus saligna
6
0.46
937
-
Bonfatti Júnior et al. (2023)
Eucalytus cloeziana
6
0.49
1030
-
Bonfatti Júnior et al. (2023)
Eucalyptus grandis x
Eucalyptus urophylla
7
0.51
-
-
Talgatti et al. (2018)
Eucalyptus dunnii
7
-
970
-
Sbardella et al. (2021)
Eucalyptus urophylla
7
-
-
313
Monteiro, et al. (2017)
Eucalyptus urophylla
8
0.49
1059
618
Paulino and Lima (2018)
Eucalyptus grandis x
Eucalyptus camaldulensis
8
0.47
-
-
Talgatti et al. (2018)
Eucalyptus grandis x
Eucalyptus urophylla
8
0.46
-
-
Talgatti et al. (2018)
Eucalyptus grandis
11
0.40
-
-
Talgatti et al. (2018)

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VICENTIN, P.G. et al. Selection of clones for pulp and paper
Rev. Inst. Flor., v. 36: e937, 2024
Figure 2. Basic density (A), fiber length (B), vessel element length (C) and Fiber wall thickness (D) of 4-year-old
Eucalyptus (11 clones). Distinct letters differ in p>0.05 by Duncan's test. The red color represents the highest value and
green the lowest.
Figura 2. Densidade básica (A), comprimento de fibra (B), comprimento de vaso (C) e espessura da parede da fibra (D)
de Eucalyptus (11 clones) aos quatro anos de idade. Letras distintas diferem em p>0,05 pelo teste de Duncan.
Clones CP02 and CP11 had the highest vessel
element length values and clone COP05 had the
lowest value. The values for vessel element length
observed by several authors. In general, we verified
that the average values (537.55 µm) observed for
the vessel element length of the clones (4-year-old)
are higher than those in the literature, but those at
a higher age (5 to 8 years old) (Table 2, Table 3 and
Figure 2C).
The basic density and the length of the fibers
showed little variability from an industrial point of
view, which is interesting because the material has
good homogeneity in these characteristics, which
favors the impregnation and removal of lignin from
the chips in the cooking processes and,
consequently, in the paper formation there will be
a better connection between fibers, thus improving
the paper in quality (Gonçalez et al., 2014). The
vessel element length observed in these woods
from these clones are somehow considered to be
large, which may favor some characteristics of
these Eucalyptus and disfavor others, in the
processes of conversion to cellulose, they are
excellent examples to improve the impregnation of
the chips (Paulino and Lima, 2018).
Among all the properties of wood, basic density
is the one most influenced by genetic material.
Other authors corroborate this pattern, as
demonstrated by Freitas et al. (2019) in their study
on the impact of site conditions on the growth and
wood quality of clonal populations of Eucalyptus.
They reported that genetic material exhibited
greater variation in growth and basic wood density
compared to environmental factors. Based on the
Diameter at Breast Height (DBH) and height data
from the sampled trees, it seems that there is
minimal variation between the clones (Table 1).
This is a factor that could potentially influence the
results of the evaluated wood characteristics.
Table 4 serve as a reference in the literature for
compare the variables fiber wall thickness, Runkel
ratio, flexibility coefficient, and wall fraction of
different species of Eucalyptus with our study.

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VICENTIN, P.G. et al. Selection of clones for pulp and paper
Rev. Inst. Flor., v. 36: e937, 2024
Table 4. Fiber wall thickness (FWT), Runkel ratio (RR), flexibility coefficient (FC) and wall fraction (WF) in Eucalyptus
spp. as a function of age. Data obtained according to the reference.
Tabela 4. Espessura da parede da fibra (FWT), índice de Runkel (RR), Fração parede (WF) e Coeficiente de rigidez (FC)
em Eucalyptus spp. em função da idade. Dados obtidos na literatura.
Species
Age
(years)
FWT
(µm)
RR
FC
(%)
WF
(%)
Reference
Eucalyptus grandis x
Eucalyptus urophylla
2
3.84
-
-
42.88%
Zanuncio et al. (2018)
Eucalyptus urophylla x
Eucalyptus grandis
4
-
1.44
42.20%
57.80%
Benites et al. (2018)
Eucalyptus grandis x
Eucalyptus camaldulensis
4
-
1.36
43.99%
56.01%
Benites et al. (2018)
Eucalyptus benthamii
5
3.4
0.77
57.39%
42.61%
Baldin et al. (2017)
Eucalyptus dunnii
5
4.3
1.07
58.96%
51.53%
Baldin et al. (2017)
Eucalyptus grandis
5
3.8
0.76
58.00%
41.99%
Baldin et al. (2017)
Eucalyptus saligna
5
3.2
0.72
68.96%
41.11%
Baldin et al. (2017)
Eucalytus benthamii
6
-
-
-
41.12%
Bonfatti Júnior et al.
(2023)
Eucalytus dunnii
6
-
-
-
62.07%
Bonfatti Júnior et al.
(2023)
Eucalytus saligna
6
-
-
-
56.74%
Bonfatti Júnior et al.
(2023)
Eucalytus cloeziana
6
-
-
-
50.03%
Bonfatti Júnior et al.
(2023)
Eucalyptus dunnii
7
3.5
0.79
58.18%
41.81%
Sbardella et al. (2021)
Eucalyptus urophylla
7
3.5
-
-
42,50%
Monteiro et al. (2017)
Eucalyptus urophylla
8
5.34
1.01
50.83%
-
Paulino and Lima (2018)
Eucalyptus grandis x
Eucalyptus urophylla
8
5.61
2.05
33.15%
66.70%
Gonçalez et al. (2014)
Fiber wall thickness showed a significant
difference between clones. Clones CP04 and CP07
had the highest fiber wall thickness and clone CP06
the lowest, the values for fiber wall thickness
observed by several authors. In general, we found
that the mean values of the fiber wall thickness of
the clones (4-years-old) are in accordance with the
literature, considering the range of ages sampled (2
to 8 years old) (Table 2, Table 4 and Figure 2D).
Trees with a thicker fiber wall have a higher
relative cellulose content than thinner-walled
fibers, with a positive correlation between wall
thickness and yield in cellulose pulp production
(Paula and Alves, 2007).

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VICENTIN, P.G. et al. Selection of clones for pulp and paper
Rev. Inst. Flor., v. 36: e937, 2024
Figure 3. Wall fraction (A) Runkel ratio (B) and flexibility coefficient (C) of 4-year-old Eucalyptus clones.
Figura 3. Fator de Runkel (A), fração parede (B) e coeficiente de rigidez (C) de Eucalyptus (11 clones) aos 4 anos de
idade.
The wall fraction, Runkel ratio and flexibility
coefficient did not show significant differences
between the different genotypes (clones) and the
mean value observed for the Runkel ratio was 0.96
(Table 2 and Figures 3A-C).
The higher the Runkel ratio value is, the less
suitable the wood is for papermaking, and the ideal
values would be less than 1, wood with higher
values should not be used for papermaking, in view
of the low degree of collapse (Burger and Richter,
1991; Baldin et al., 2017). We can see that most
clones had a factor less than 1, except for clones
CP06 and CP07, where the factors were greater
than 1 (Table 2).
The average value presented for the wall
fraction was 46.14% (Table 2). Woods with fibers
with a higher wall fraction index result in greater
dimensional instability, however, this high index
provides greater mechanical resistance of the wood
(Zanuncio et al., 2018). Fibers with a high wall
fraction are indicated for the manufacture of tissue
paper, as they absorb more liquids (Bonfatti Júnior
et al., 2023).
For the flexibility coefficient, the mean value
presented was 53.86% (Table 2). The higher the
flexibility coefficient, the greater the flattening and
better the cell shaping, and a high value also means
the existence of thinner walled cells (Burger and
Richter, 1991).
With the aim of classifying the clones into
groups according to their characteristic similarities,
considering all variables under study, a Cluster
analysis and principal component analysis (PCA)
were carried out (Figures 4 and 5).

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VICENTIN, P.G. et al. Selection of clones for pulp and paper
Rev. Inst. Flor., v. 36: e937, 2024
Figure 4. Cluster analysis of Eucalyptus clones dendrogram.
Figura 4. Dendrograma de cluster dos clones de Eucalyptus.
In the cluster analysis, it was possible to group
the clones based on similarity where, according to
the analyzed properties, the clones were divided
into two clusters, the first cluster with four clones
and the second with six clones (Figure 4).
According to the dendrogram, we can separate the
clones in group 1: clones 7, 8, 9 and 10 and group
2: clones 1, 2, 3, 4, 5, 6 and 11. The properties
Runkel Index (RR), Wall Fraction (WF) and
Stiffness Coefficient (FC) had a greater influence
on the grouping of clones and wall thickness and
basic density had a lesser influence (Figures 4 and
5).
Figure 5. Principal Components Analysis (PCA) of the properties of wood of Eucalyptus clones. The greater the intensity
of the red color, the more the property contributes to the grouping. The magnitude is represented by color intensity.
Additionally, the smaller the angle between the vectors, the stronger the relationship between the variables. The longer
the vector and closer to the outer circle, the greater the significance of the variable represented by the vector.
Figura 5. Análise dos componentes principal (PCA) das propriedades da madeira de clones Eucalyptus. Quanto maior a
intensidade da cor vermelha, mais a propriedade contribui para o agrupamento. A magnitude é representada pela
intensidade da cor. Adicionalmente, quanto menor o ângulo entre os vetores maior é a relação entre as variáveis. Quanto
mais longo o vetor e próximo do círculo externo, maior e a significância da variável representada pelo vetor.

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VICENTIN, P.G. et al. Selection of clones for pulp and paper
Rev. Inst. Flor., v. 36: e937, 2024
Therefore, the reference to the suitability of
wood for pulp and paper manufacturing in terms of
coefficients and factors were more efficient to group
Eucalyptus clones. This was also addressed by
Baldin et al. (2017). This result demonstrates that
clones can be separated by cluster through cluster
analysis considering the wood properties analyzed.
We can highlight the importance of new
comprehensive studies of each clone, to define the
best use of its wood in terms of the productivity of
forest plantations and the quality of the wood for the
region of Palmital, SP. These studies will support
the implantation of future forests by rural producers
interested in diversifying their activities.
Figure 5 depicts the correlations among the
variables that demonstrated significance in the first
and second ordination axes, accounting for 77.06%
of the explained variance in PCA. Axis 1
contributed 52.21% to the overall variability, while
axis 2 contributed 24.85% to the variability.
The PCA analyses indicate that the vector
representing fiber wall thickness is correlated with
the vectors representing basic density, suggesting
that these characteristics influence wood density.
This relationship is widely recognized in the
literature, as fibers with thicker walls contribute
positively to higher wood density (Hoadley, 2000;
Wiedenhoeft and Eberhardt, 2021). The vector
representing the flexibility coefficient is inversely
correlated with the vectors representing Runkel
ratio and wall fraction. These results, in accordance
with the values presented by Trianoski (2012),
allow us to infer that in materials with a high
flexibility coefficient value, e.g., >75%, indicating
good collapse between the cells, a substantial
contact surface, and effective union between the
elements of cell walls, a lower Runkel ratio will be
found. This makes the material more flexible, with
excellent accommodation capacity and in excellent
condition for paper production. Additionally, a
lower wall fraction makes the cell walls less rigid
and more flexible, but with lower interconnection
capacity, resulting in greater tensile and bursting
resistance and lower tearing resistance.
4 CONCLUSIONS
According to the results presented, we can
conclude that:
-at 4 years of age there were significant
differences for: basic density, fiber length, vessel
element length and fiber wall thickness of the
different clones;
-the Runkel ratio, flexibility coefficient and wall
fraction did not show significant differences in the
wood between the different clones;
-through of analysis to the dendrogram of
Cluster one can separate the clones in two groups;
-Runkel Index, Wall Fraction and Stiffness
Coefficient had a greater influence on the grouping
of clones;
-basic density and fiber wall thickness had little
influence in the grouping of clones.
We can highlight the importance of new
comprehensive studies of each clone, to define the
best use of its wood according to age.
5 ACKNOWLEDGEMENTS
The authors thank Sonia Regina Godoi Campião
and Wilson Aparecido Contieri for laboratory
assistance (Instituto de Pesquisas Ambientais. São
Paulo, SP, Brazil).
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