Kaba et al. /Journal of Tropical Forestry and Environment Vol 12, No. 02 (2022) 10-21

Correspondence: gkabaa17@gmail.com

Density and Seasoning Characteristics of Pinus caribaea Lumber

Grown at Suba Forest, Oromia, Ethiopia

Gemechu Kaba1*, Getachew Desalegn1, AntenehTesfaye1, Mahadi Mussa1, Tsegaye
Wubshet1 and Getachew Mezgebu1

1Forest Products Innovation Center, Ethiopian Forest Development, Addis Ababa,

Ethiopia

*gkabaa17@gmail.com

Date Received: April 30, 2022 Date Accepted: October 03, 2022

Abstract

Determination of the seasoning characteristics, physical and mechanical properties of lumber

species is helpful in identifying the main factors affecting the quality, suitability and overall
performance of wood and wood-based products. The Pinus caribaea has been considered as

industrial lumber species and there is a little study conducted in identifying the physical

characteristics which on turn affects the quality of product derived from the lumber. Therefore,
this study aimed at evaluating the density and seasoning characteristics of P. caribaea lumber.

Sample trees were harvested from Suba Forest Oromia, Ethiopia. The experiments were carried
out using air and kiln seasoning methods. To measure the initial moisture content, seasoning rate,

shrinkage, wood density, and seasoning defects, six replicates of samples from each tree portions

were prepared when green and promptly weighed. Analysis of variance (ANOVA) has been
employed in interpreting the experimental results. The obtained results have shown that the mean

initial moisture content for air stacks was 78.2% while for the kiln seasoning stacks 82.9%.
Seasoning time for sawn boards of 3 cm thick to reach 17% moisture continent (MC) required

61 days, while for kiln seasoning took 4.3 days to reach 14.62% MC. This showed that kiln

seasoning was about 14 times faster than air seasoning. In air seasoning the MC (%) of the lumber
from 78.2% to 16.9%; and, the obtained mean values of shrinkages were tangential (3.6%), radial

(1.9%) and volumetric (5.4%). The initial moisture content (IMC) and green density (GD) of the
lumber were significant difference along the tree height at a 95% probability level. The seasoning

rate % and final MC (%) along the tree height were significant difference at 95% probability

level, while the seasoning rate % and final MC were significant difference between seasoning
methods at 99% probability level. Seasoning defects such as cup, bow, twist, and crook were

observed on kiln seasoned. In addition, end checks and splits were observed on air seasoned
boards. Therefore, the experimental factors should be monitored and optimized properly to obtain

the lumber with good quality and utilize it for different purposes, including construction and

industrial applications.

Keywords: Density, lumber, moisture content, seasoning, shrinkage characteristics, Pinus
caribaea

1. Introduction
In Ethiopia, the demand for wood-based products in 2017 was measured in terms of

equivalent volume of consumed round wood and it was estimated to be 114 million cubic meters
(UN-FAO, 2019). The demand and supply of industrial round wood in Ethiopia were 7.4 and 3

million m3, respectively (Ministry of Environment, Forest and Climate Change [MEFCC], 2018;

United Nations - Food and Agricultural Organization [UN-FAO], 2019). This shows there is a

Kaba et al. /Journal of Tropical Forestry and Environment Vol 12, No. 01 (2022) 10-21

wide gap between the demand and supply. The gap is being filled by imported lumber and
unsustainable harvesting and utilization of natural and plantation forests (Environment, Forest

and Climate Change Commission [EFCC], 2020); and this could jeopardize the natural
ecosystem and biodiversity thereby inducing overexploitation of the dwindling forest resources.

Moreover, the potential lumber species have been introduced and planted continuously all
over the country to fill the gap and bring about sustainable utilization of the country’s plantation

forests and woodlot resources (Gemechu et al., 2018). Among these tree species, Pinus caribaea
is a well-known and substantial industrial lumber species that has been planted and adopted in

Ethiopia to achieve the goal of plantation development and sustainable utilization of forest

resources (Mebrate, 2006).

The P. caribaea (Family Pinaceae) is an evergreen, monoecious, and medium-sized tree that

is 20 - 45 m in height, 60-135 cm in diameter and bole branchless of 21 m. P. caribaea is fast
growing species with a mean annual volume increment of 10 - 40 m³/ha and 15-25 years rotation

for sawn wood, veneer, large posts and pulpwood. The wood properties of P. caribaea shows
variations as heavy, hard, narrow ringed and resin saturated at one end of the spectrum to soft,

light, wide ringed and almost lacking in latewood and resin at the other end. The tree is usually

straight, cylindrical, bark surface reddish brown to pale brownish grey, inner bark very resinous,
crown thin, rounded to pyramidal, slightly spreading, twigs orange brown, later turning gre y-

brown (Oteng-Amoako and Brink, 2008; Orwa et al., 2009).

Furthermore, P. caribaea is grown in 1000 -1500 m altitude above sea level (asl), in areas
with a mean annual temperature of 20 - 27°C, an average annual rainfall of 650-4000 mm, and a

dry season of up to 6 months. The tree is moderately tolerant to wind and can be planted near the

coast. It grows on a wide variety of soils like loams or sandy loams, sometimes with high amounts
of gravel and generally well drained (Oteng-Amoako and Brink, 2008; Orwa et al., 2009).

According to some authors the species is native to the Caribbean area, Cuba, Honduras, Bahamas
and Colombia, Guatemala, Mexico, Nicaragua and Panama. As an exotic plantation species P.

carebea is planted fairly widely in Australia, Brazil, Canada, India, Indonesia, United States of

America, Venezuela, south, east, east west and central parts of African countries including
Ethiopia (Orwa et al., 2009).

The effective, efficient and sustainable utilization of the lumber species (i.e., P. caribaea)

necessitated adequate knowledge and deep understanding of its natural variations, density and

seasoning characteristics, physical and mechanical characteristics and its industrial applications
(Nascimento et al., 2018). Hence, generation of appropriate technological information regarding

the tree seasoning and the selection of suitable utilization method is of prime importance while
enhancing the service life of the product(s). In light of this explanation, the intended study was

carried out to generate technical information (i.e., density and seasoning characteristics) and

selecting appropriate methods for utilization of the lumber species, P. caribaea, grown at Suba
Forest of Oromia Forestry and Wildlife Enterprise (OFWE), Ethiopia.

2. Materials and methods
2.1 Description of the study site
Sample trees of P. caribaea were harvested at the age of 44 from Suba Forest of OFWE. Suba

Forest is located 40 km west of Addis Ababa and lies within longitude and latitude coordinates
of 38°31’– 39’E and 08°54’N–09°04’N, respectively, and the altitude ranges between 2330 and

3300 m asl. The mean annual rainfall of 1100 mm and the mean temperatures (min and max) are

15 c° and 22c°, respectively. The tree species is originated from the Bossum provenance of

Kaba et al. /Journal of Tropical Forestry and Environment Vol 12, No. 01 (2022) 10-21

Holland and currently available in Ethiopia at Belete, Hamulo and Menagesha -Suba (Mebrate
Mihreiu, 2004; Mebrate Mihertu, 2006)

2.2 Trees harvesting and test samples preparation

Twelve sample trees with good morphological characteristics and free from visible defects
were selected, harvested and cross-cut into a series of 5 m long logs up to top merchantable

diameter of 20 cm. The selected trees have a mean height of 22 m and 30 cm diameter. Harvested

logs while green (> 30% MC) were transported to Laboratory of Forest Products Innovation
Center (FPIC), Addis Ababa, for the preparation and testing samples. Logs were flat sawn to 3

cm thick boards and converted to samples with appropriate dimensions for each wood
characteristic (Moisture content, seasoning rate, seasoning defects, shrinkage and density) tests

following the ISO standards (ISO 3129, 1975; ISO 3130, 1975; ISO 3131, 1975; Denig et al.,

2000; FPL, 2010; Moya et al., 2013).

2.3 Lumber stacking for air and kiln seasoning
Sawn boards from sawmill area were transported to the air seasoning yard and kiln seasoning

chamber areas (Figure 1). Boards were sorted according to their thickness, width, and types

(heart, sap, tangential and radial boards). Then, lumber stacked horizontally in vertical
alignments separated by well- seasoned standard stickers. Stickers were put at equal distance (75

cm across each layer of lumber) and aligned vertical board on board from bottom of the stack to
the top. While stacking boards, care was taken to ensure free circulation of fre sh air all around

each stack and board. In addition, the control sample boards were distributed properly and

positioned in the pockets of the different layers (i.e., bottom, middle and top) of each stack to
represent the different zones/layers in the stack (Figure 1).

Figure 1: Air seasoning stack (1a) and Kiln seasoning stack (1b) at the entrance of the

kiln chamber

Boards for air seasoning were stacked on firm level foundation 45 cm above the ground,
under open-sided shed without direct exposure to moisture, rainfall and sunshine (Figure 1a).

The boards were aligned in a north-south direction where the ends were not exposed to the

direction of the wind. Boards for kiln seasoning were stacked out of the kiln on the transfer
carriage having dimensions of 1.6 m width, 0.30 m height and 2.7 m length and then placed

in the kiln-seasoning chamber by sliding the stack on the rail (Figure 1b). Top loading (heavy
stones) weighing about 50 kg/m2 was applied on top of the air and kiln seasoning stacks to

minimize warping of the boards as seasoning progresses. The Kiln Schedule adapted from

Kaba et al. /Journal of Tropical Forestry and Environment Vol 12, No. 01 (2022) 10-21

Boone et al. (1988) having a serious of temperature and relative humidity at different
corresponding MC levels was applied (Table 1)

Table 1: The employed kiln schedule

Step Moisture

Content (%)

Dry-bulb

Temperature

(°F)

Wet-bulb

Temperature

(°F)

Relative

Humidity

(%)

Equilibrium

Moisture

Content (%)

1 Above 50 60 56 82 14.2
2 50 to 40 60 54.5 75 12

3 40 to 35 60 51.5 64 9.6

4 35 to 30 60 49 55 8

5 30 to 25 65.5 51.5 49 6.8

6 25to 20 71 54.5 43 5.8

7 20 to 15 76.5 57 39 5.1

8 15 to Final 82 54.5 26 3.5

Source: Boone et al., 1988.

2.4 Lumber characteristics determination
Initial moisture content determination

Six replicates of Samples from each tree portion were prepared while green and

immediately weighted to determine initial moisture content of the stack. A well -ventilated
oven machine/ chamber with trays having open grids was used to allow free air circulation

around the test pieces while keeping the seasoning temperature constant at 105°C. Drying

and re-weighing of samples was carried out continuously at four hours interval until the
difference between two successive weights of each specimen became constant (0.000 - 0.200

g) and the final weights were taken as the oven- dry weights (ISO 3130, 1975; FPL, 2010).
Afterwards, the moisture content of air and kiln seasoning stacks were determined using the

following formula.

𝑀𝐶 (%) = (
Green weight−Oven dry weight

Oven dry weight
) × 100 (1)

After initial MC determination, the control sample boards were weighed, analytically

determined oven dry weights were calculated and the control samples placed into the stack.

During air seasoning the control samples were re-weighed at a week interval until the average
final moisture content of the stack reached final moisture content (about 12%), which is the

equilibrium moisture content for in-and out-door purposes and standard for comparison
within and between lumber species. During kiln seasoning test, samples were weighed,

moisture content was calculated, psychrometers were regulated, steaming was done, and the

direction of the fan changed at 8 hours interval (i.e., three times in 24 hours) to allow uniform
air circulation. The process was continuous until the final MC reached. This is used to control

the seasoning process and maintain the quality of seasoned lumber (FPL, 2010; Moya et al.,
2013).

Rate of seasoning determination
Air and kiln seasoning rates of the species was estimated from the MC samples of the

species. Seasoning rate (%/hour) = IMC-FMC (%)/Drying time (Hour) (Loulidi I. et al., 2012)
where, IMC-initial moisture content and FMC- final moisture content. The Air and Kiln

seasoning rates classification lumber for the lumber was done based on the adapted literatures

(Longwood, 1961; Farmer, 1987).

Kaba et al. /Journal of Tropical Forestry and Environment Vol 12, No. 01 (2022) 10-21

Shrinkage characteristics determination
Twenty samples of the lumber species with the dimension of 2x2x3 cm (ISO/DIS 4469,

1975) were seasoned in the oven machine at the temperature of 105C until a constant weight

was obtained for each sample. Initial dimensions and weights of all the shrinkage samples

were measured and put in the oven. Measurements of weights were continuous until the

difference between the two successive weights of each specimen was constant (0.000 - 0.200
g). Then, the final weights were taken as oven dry weights and final dimensions were

measured Shrinkage of each specimen at tangential, radial, longitudinal directions and
volumetric were determined from green condition to 12% MC and from green to 0% MC

using the formula in (Equation 2):

Shrinkage% = (Change in dimension
Green dimension

x 100) (2)

Finally, the rate of tangential shrinkage to radial shrinkage (coefficient of anisotropy)

was calculated to know the tendency of the species to present warping, cracking and splitting
during seasoning. According to Acosta et al (2008) the higher this ratio from the value of one

will be the higher to present these defects during seasoning of the wood.

Density determination

The sampling procedures and measurements applied during shrinkage experiments as
stated earlier were used to determine the density values of the species using mathematical

formulas at different MC and sample conditions (i.e., Green, oven dry and seasoned to 12%
MC). Basic density was determined based on green volume and oven dry weight (ISO/DIS

3131, 1975). The dry density values were converted to standard 12% equilibrium MC (Table

2) by applying the formulas adapted from (ISO/DIS 3131, 1975; Denig et al., 2000; Reeb and
Brown, 2007; FPL, 2010; Moya et al., 2013). Density value of the species at 12% MC was

classified based on the adapted standard classification from Farmer (1987).

Seasoning defects determination
Natural, initial and after seasoning defects of lumber species including knots, cup, bow,

twist, end split, end and surface checks were measured and determined using digital caliper,

ruler and tape meter. Seasoned boards were properly piled in the air seasoning yard, board on
board, without stickers between them. Boards were handled and conditioned well without

direct exposure to moisture and sunshine to avoid/minimize dimensional movement
(shrinkage and swelling), seasoning defects and biodegradation attack.

2.4 Data analysis
The measurements of dimension (Length, width and thickness) and weight were helped

to determine the following parameters: (i) moisture content (%) at green, current and final,
(ii) density (gm/cm3) at green and air-dry conditions, (iii) rate of seasoning (%/day), (iv)

shrinkage (%) from green to 12% MC and green to 0% MC in tangential, radial and
longitudinal directions and volumetric, and (v) initial and seasoning defects (observation and

measurements). Analysis of variance (ANOVA) for shrinkage, density and seasoning

characteristics was performed at 95% confidence interval. Significant differences among tree
height were determined by Duncan’s homogeneity groups. Statistical analysis was performed

using the statistical Package for the Social Sciences (SPSS) 20 version.

3. Results and Discussion

Kaba et al. /Journal of Tropical Forestry and Environment Vol 12, No. 01 (2022) 10-21

3.1 Lumber appearance
The wood of P. caribaea showed different lumber characteristics. The lumber

appearance revealed the creamy white sapwood and the dark brown heartwood (Figure 2a).

Figure 2: Appearance (a) and high resin content (b) from P. caribaea lumber

3.2 Moisture content

The mean initial moisture content of P. caribaea lumber was 78.2% for air seasoning and
82.9% for kiln seasoning; whereas, the final mean moisture content for air and kiln seasoning

stacks were 16.9% and 12.4 %, respectively. During air seasoning, the mean initial MC slightly

varies along the height of lumber. The bottom part of P. caribaea tree had 79.4% MC, middle
part had 77.7% MC, while top part had 77.6% which is almost similar with the middle part

(Figure 3). The trend of MC along the height of the tree varies irregularly.

Figure 3: Pinus caribaea lumber initial (green) (IMC) and final seasoned MC (FMC) (%)

3.3 Shrinkage characteristic
When seasoning the P. Caribaea lumber from green to 12% MC, the obtained mean

Mini intial and final
MC for air drying

Mini intial and final
MC for kilin drying

Mini intial MC along
the hight of the tree

Moisture content of wood

M
o
is

tu
re

c
o
n
te

n
t
(%

)

Initial

Final

Bottom

Middle

Top

Kaba et al. /Journal of Tropical Forestry and Environment Vol 12, No. 01 (2022) 10-21

percentage values of shrinkage were tangential 4% (small), radial 1.9% (very small) and
volumetric 5.4% (small); whereas, seasoning the lumber from green to 0% MC, the tangential,

radial and volumetric shrinkage values of 6%, 3.2% and 9%, were obtained, respectively
(Table 3). The shrinkage values of seasoned wood at 12% MC vary from 4.7-12.7% for

tangential shrinkage and 2.1-7.9% for radial shrinkage. Tangential shrinkage is generally 1.5

to 2 times greater than radial shrinkage. The ratio of total tangential shrinkage to total radial
shrinkage (T/R) was used as an index of dimensional stability. The ratio of tangential to radial

shrinkage was 1.9% which was higher than 1.5 (Table 3). Ratios higher than 1.5 considered
pronounced (Acosta et al., 2008). This pronounced differential shrinkage is likely to cause

wide splits, checks and distortions if the necessary precautions are not taken to seasoning of

P. caribaea lumber species.

Figure 4: Shrinkage characteristics values (%) at 12% MC reduction

3.4 Density characteristics
The mean density of P. caribaea lumber species at green (initial), basic, oven dry

conditions and when seasoned to 12% MC were 690, 383, 350 and 660 kg/m3, respectively

(Table 4). Based on the density value (660 kg/m3) at 12% MC, the lumber species can be
classified under heavy density (650-800 kg/m3) category. According to Oteng-Amoako and

Brink (2008), wood properties show large differences between sites and between trees. The

wood is moderately light weight to fairly heavy, with a density of 350-820 kg/m³ at 12%
moisture content. The wood from slower-growing trees from natural stands has a higher

density and lower resin content than the wood from faster-growing trees from plantations
(Oteng- Amoako and Brink, 2008; Orwa et al., 2009). For the same species, similar value

of density was observed in the rage of 450 – 650 kg/m3 (Udoakpan, 2013).

3.5 Air and kiln seasoning rate of P. caribaea lumbers
The time required for air seasoning of P. caribaea sawn boards that have 3 cm
thickness to reach to about 17% MC was 61 days, while kiln seasoning using the kiln that

operates at a temperature range of 40-70ºC took 4.3 days to reach 12.4% moisture content.

Kiln seasoning rate was 0.62%/day. Thus, the kiln seasoning was 14 times faster than the
air seasoning. The species was classified as very rapid in air and kiln seasoning. The kiln

seasoning significantly shortens the seasoning time required to season the lumber to ~ 12%
MC (Getachew D et al., 2015)

Lumber directions/surfaces

Tangential Radial Longitudinal Volumetric

Kaba et al. /Journal of Tropical Forestry and Environment Vol 12, No. 01 (2022) 10-21

Table 2: Summary of ANOVA on moisture content, densities and shrinkages of P. caribaea
lumber

Source of Variation DF Mean square and statistical
significances

Shrinkage from green to 12% MC (%)

IMC GD BD OD Density 12% MC Tangentia
l

Radial Volume
tric

Position2 3850.18
*

0.043* 0.004 ns 0.004 ns 0.006 ns 1.16 ns 0.132ns 1.925 ns

Note: ns-not significant at p<0.05, *-significant at p<0.05. Where: - DF- degree of freedom,

IMC-Initial moisture content, GD-Green density, BD-Basic density, OD- Oven dry density

The initial moisture content (green) (IMC) and green density (GD) along height of the tree

were significant (p<0.05) at 95% probability level, while density (basic and at 12% MC),
tangential, radial and volumetric at 12% MC were non- significant (Table 2).

Table 3: Summary of ANOVA on seasoning characteristics of P. caribaea lumber

Source of

variation

DF Mean square and statistical significances

Seasoning rate %/

(hour)

Final MC (%) Initial MC

(%)

Seasoning rate

%/hour

Position 2 229051.56* 60.436* 37.228ns 0.006ns
Seasoning

method

1 4412437.770** 122.899** 132.963ns 3.713**

Note: ns-not significant at p < 0.05, *-significant at p < 0.05, highly significant at p < 0.01.

Where: DF- degree of freedom, MC- moisture content

Seasoning rate (%/hour) and final MC (%) along height of the tree and seasoning methods

were significant (p < 0.05) at 95% probability level, while seasoning methods were significant
(p < 0.01) at 99% probability level (Table 3). According to Oteng-Amoako and Brink (2008),

the wood of P. caribaea exhibits good quality under air seasoning, though the end splits may

occur during seasoning. Boards of 3 cm thick required about 6 weeks (1.5 month) to air dry
lumber from green to 16.88% moisture content. This is similar with the study carried out in Fiji

that around six weeks was required to dry 3 cm thick lumber from green (170% MC) to 20%
MC) in open air (Plumptre, 1984). To dry P. caribaea in conventional kiln up to 12% moisture

content took 3-4 days; in average the kiln seasoning rate for the species was 0.62%/hour.

3.6 Seasoning defects

During both air and kiln seasoning methods, different defects were recorded on P. caribaea
lumber. Even if the degree varies, defects like warp (cup, bow, twist, and crook/spring) were

seen on kiln-seasoned boards. In addition to the above defects, end splits were observed on air

seasoned boards. During air seasoning crook/spring was the serious defect while on kiln sea-
soned boards twist was the more pronounced defect (Table 4). Kiln seasoning is preferred over

air seasoning to produce better-quality boards at a lower cost of operation, even though some
seasoning defects on seasoned boards have been observed. The dead knot which is the natural

defect was the dominant type on P. caribaea lumber species.

Kaba et al. /Journal of Tropical Forestry and Environment Vol 12, No. 01 (2022) 10-21

Table 4: The extent of mean seasoning defects in air and kiln seasoning stacks.
Seasoni

method

Warp (mm) Checks (mm) Splits

Dia.

(mm), L.

(cm)

Knots Other

defects

occur

Cup Bow Tw

ist

Cro

Surface

check

d
che

End

split

d
spl

Knots

Dia.
(mm)

No.

of
knots

Air 2 4 7 8 --- --- 2 17 34 5 Wane

Klin 3 2 12 3 --- --- --- --- 30 5 Wane

Proper stacking using standard and well-seasoned stickers, end sealants or plastic end cleats,

top loading/ adjustable strapping are paramount for preventions or remedies of seasoning to
minimize these defects.

3.7 Comparison of P. caribaea lumber with commercial lumbers grown in Ethiopia

Comparable lumber species with P. caribaea in terms of the rate of seasoning by kiln
method (4.3 days) were Eucalyptus viminalis, Eucalyptus saligna and Morus mesozygia (4

days), Ocotea kenyensis (4.4 days) (Getachew Desalegn et al., 2012; Getachew Desalegn et

al., 2015; Getachew Desalegn and Gemechu Kaba, 2017; Gemechu Kaba and Getachew
Desalegn, 2020). Besides, for the density at 12% MC (660 kg/m3), comparable species with P.

caribaea were Eucalyptus fastigata (650 kg/m3), Eucalyptus obliqua (670 kg/m3), Eucalyptus
viminalis (670 kg/m3), Morus mesozygia (670 kg/m3) (Getachew Desalegn et al., 2012;

Getachew Desalegn et al., 2015; Getachew Desalegn and Gemechu Kaba, 2017; Gemechu

Kaba and Getachew Desalegn, 2020).

4. Conclusion and Recommendations

Pinus caribaea has lumber and several non-lumber forest products and services. The

species has comparable wood with many indigenous and home-grown exotic lumbers of
Ethiopia in terms of density, seasoning rate and shrinkage characteristics. Different seasoning

defects were observed that need care during lumber seasoning. Lumber shall be seasoned using
kiln seasoning method to shorten seasoning time, better maintain wood quality and suitability

for different applications. In this study, the density and seasoning characteristics of Pinus

caribaea lumber was evaluated; and it has been observed that the moisture content (MC),
seasoning time, seasoning characteristics and density of wood are amongst the main factors

that can highly influence the quality, suitability and overall performance of the lumber.

The main experimental factors considered in the experimentation were percentage of

moisture content at green, current and final moisture content, the seasoning rate, seasoning
shrinkages (i.e., in tangential, radial and volumetric directions), density of the lumber at green

and air-dry conditions, and associated seasoning defects have been observed. This implies that
kiln seasoning method is more effective and hence, preferable to the air seasoning of the P.

caribaea lumber so as to obtain lumber products with less defects, better quality and minimum

operational cost. Therefore, kiln seasoning method is recommended for seasoning the lumber
species in wood and forest products processing industries, and construction sectors thereby

ensuring the effective, efficient and sustainable utilization of the considered P. caribaea tree.

Kaba et al. /Journal of Tropical Forestry and Environment Vol 12, No. 01 (2022) 10-21

For future work, the research should be conducted regarding the presence of high resin in P.
caribaea lumber and its effect on the lumber quality. The improvement of silvicultural practice

is necessitated besides expanding plantation in the country (Ethiopia).

5. Acknowledgement
The authors acknowledged the Ethiopia Forest development for the financial support

solicited from the Government of Ethiopia. Oromiya Forestry and Wildlife Enterprise (Head

Office, Finfinnee Branch and Suba Forest District) are highly appreciated for permitting the
selection, harvesting, and transportation of sample trees to Addis Abeba for additional

processing and research. The authors would also like to thank Mr. Dagnachew Genene for

reviewing the draft manuscript. Finally, we would like to express our gratitude to all of the
coordinating, technical and supporting staff members of the Forest products Innovation Center

for their respective participation and support during sample trees selection, harvesting, log
transporting, log sawing, sample preparation, testing, saw-doctoring, and logistics supports in

their respective domains.

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