Welcome to the26 IUFRO World Congress
thStockholm, Sweden, 23–29 June 2024

Effect of Topographic Conditions on TeakHeartwood Quality in MountainousArea
Dr. Simone VONGKHAMHOForest Research Center
National Agriculture and Forestry Research Institute
Vientiane, Lao PDR

Table of Contents
1. Introduction
2. Research area and methodology
3 Results
4 Summary1. Introduction
1.1. Teak• Teak (Tectona grandis L.f) is a large tree up to40 m tall and up 2 m in diameter and has a fast
growth. Leaves are shed in the dry season. Teakis a light-demanding tree and grows in mixeddeciduous forests with Xylia xylocarpa,Lagerstroemia spp., Afzelia xylocarpa,Pterocarpus macrocarpus and bamboo.
Flowering in May-August and fruiting is inDecember – April (Palanisamy et al., 2003).
• Teak is a native tree species in Asia, and it has anatural distribution area range from India,
Myanmar, Thailand to northwestern Lao PDR(Kaosa-ard, 1989; Tanaka et al., 1998).

Natural teak forest in Northwestern Lao PDR(Photo: FRC, March 2021)

• Teak is a globally commercial hardwood treespecies. Teak wood exhibits a high timber
quality owing to properties such as lightness
with strength, stability, durability, resistanceto termites and fungi, and high adaptability toenvironmental variations (Kaosa-ard, 1989;Hansen et al., 1997; Jerez et al., 2017).
• Hence, it is widely used in the building ofboth outdoor and indoor furniture, ships,decorative veneers, etc. (Thulasidas et al.,2006; Midgley et al., 2012, 2015). Due tothese widespread applications, the productionof high-quality timber with a high yield isessential for successful teak plantations

Teakwood processing factoryin northern Lao PDR. The
products export to Thailand

1.2. Application of teak1.3. Distribution of teak
• Teak has been planted in a large diversity of site
conditions inside and outside of its native area
across 70 tropical countries for many centuries. In2017, the teak plantation area grew up to 6.89
million hectares (Kollert et al., 2017).
• In the Lao People’s Democratic Republic (PDR),
teak has been planted since 1942 (Keonakone,2005; Midgley, 2006). However, over the past
decades planted teak had not been expanded until
1990s, government has strongly been promoted
this species for rehabilitation purpose. In 2019,
the total teak plantation area increased to 40,000
hectares (Pachas et al., 2019).
Mature Planted Teak Forest of 79 years oldin southern Lao PDR (Photo: FRC, Jan. 2021)

1.4. Controlling factors of teak growth• Teak growth and development is controlled by various
factors, including genotypes (Kaosa-ard, 1989; Sreekanth et al., 2014),
good silviculture practices (Perez et al., 2005; Pachas et al., 2019), andenvironmental factors (e.g., rainfall, temperature, andwind), geology, topography, soil, sunlight, and moisture(Tanaka et al., 1998; Kokutse et al., 2010).

• In general, soil-site conditions are significant factors
influence the teak growth and development; for example, it
has a good growth in fertilized soil with rich calcium
contents, well-drainage soil interaction with gentle slope
and bottom of valley (Tanaka et al., 1998; Watanabe et al.,2010).
• In Lao PDR, planted teaks have been established invarious site conditions across the country; mountainous
land in northern part, flat land in central and southern partand southern plateau land of Bolaven. However, northernpart is covered a larger scale of planted teak shared 64% of
total area (Phongoudome et al., 2012; Boer et al., 2016; Maraseni et al., 2018).

Mature teak plantation of 53 years in Luang
Prabang province (Photo: Imaya, 2019Heartwood (Hw) content, color, density and shrinkage

Teak timber
quality

1.5. Problem
Treequality

Tree
GrowthHeartwood
quality

Farmer’s planted teak of 23 years old

Site and standCharacteristics

What kind of effect?

Luang Prabang’s Teak forest(98% belong to farmers & private sector)

Silviculture

Environmentalfactors• High Stand density• Soil Properties

Tree Age&(1100 – 2500 tree ha-1)• Insufficientmanagement(large range ofsuitable soil for teak)• Sitecharacteristics

1.6. Previous study of teak in Lao PDR• Although the government’s strategy promoted the increase in teak plantation,
the international price of Lao’s teak timber has been low (ITTO, 2019), owing
to the limited information available on the suitability of environmental
conditions for teak plantation compared with Thailand (Tanaka et al., 1998;
Sukchan et al., 2012) and Myanmar (Htoo et al., 2020).
• Over the past decades, many researcher had been studied on various matters ofteak in Lao PDR; genetics (Keiding et al., 1986; Kjaer et al., 1995),
silviculture manage techniques related to growth and yield of teak
(Keonakone, 2005; Dieters et al., 2014; Pachas et al., 2019), and wood quality(Wanneng, 2019). These studies were not included to site condition variables.
Therefore, the research on environmental factors influence teak timber quality
in Lao PDR is very rarely1.7. Purpose of the study
This study aimed to determine the effect of site conditions on the growthand quality of teak in northern Laos through investigating the suitablesite conditions for teak plantations in the north of Lao PDR. The specificobjectives are: To investigate the effect of topographic conditions onteak heartwood quality in mountainous areas

2. Research Area and Methodologies
2.1. Research site
• A 31-km transect line (pinkcolor) was drawn, whereas 16
km west of Luang Prabang city.
The line began from the flat landof Mekong riverside in theThinxom village, Luang Prabang
to the highland area ofKiewtaloun village in Xieng
Ngern district.

The research site is in a region with a tropical monsoon climate comprising
two distinct seasons; The mean annual rainfall was 1628 mm; the meanannual temperature was 26.4 C ; the average relative humidity was 79%.

• 61 individual plantations weretargeted along a transect line, site
elevation range from 287 to 1057
m.a.s.l.
Map of research site

2.2. Temporary sample plots• For assessing the treetimber quality and tree age• A plot is established ineach target plantation.
• Plot area : 400 m2

Plot size of 20 m x 20 m

2.3. Tree measurement•The diameter at thebreast height (DBH)
was measured usinga measuring tape.

•Total Height andBole Height weremeasured using aheight measurer(Vertex IV, Haglöf,Sweden)

Using Vertex to measure treeheight2.4. Plot sampling• 49 sample plots in total with stand age > 10 years old, site
elevation <900 m.a.s.l and without damages in heartwood wereselected from target plantations.
• 147 short log samples obtained from the felled tree (three tree
per plot) using for heartwood quality assessment.

2.5. Assessing heartwood content

Frequency of tip crosscut discs size of ≥ 12 cmin diameter• In Lao PDR, the marketable size of the teak isapproximately ≥ 12 cm in diameter (Hopewell et al.,2014). In this study, we focus on examining theheartwood content of the commercial volume. A
total of 1177 sample discs of ≥ 12 cm in diameterfrom 147 sample trees obtained from scanningphoto file of the crosscut discs• The selected disc photos were analysed using
Imgviewer software to measure the radius ofheartwood and stem from outer bark to pith in four
directions: north, east, south, and west.
• Mean stem (under and over bark) and heartwoodradius was obtained from four direction.
• Heartwood content was calculated using geometricformula (Tewari et al., 2013).

2.6 Assessing heartwood properties and colora. Wood specimen preparation
AShort log

147 cross-sectional
samples (CSS)B

Taking 2 specimens from each
A CSS, having 294 specimens in
total for measuring basic
density and shrinkages
Taking a specimen from each
B CSS, having 147 specimens in
total for assessing heartwoodcolor

b. Basic density and shrinkage measurement
Cleaning and Marking
crosscut line on woodsurface. Preparing thedigital caliper and scales

Oven-drying the woodspecimen at 100℃ within
24 hours

Measuring the dimension
and weight of green
wood specimen

Air-drying the woodspecimens at room
temperature for a week

Measuring the dimension
and weight of oven-driedwood specimens

Basic density and shrinkages was calculated using
following equation (Miranda et al., 2011):
𝑂𝑂𝑂𝑂𝑂𝑂𝑂𝑂−𝑑𝑑𝑑𝑑𝑑𝑑 𝑊𝑊𝑊𝑊𝑊𝑊𝑊𝑊𝑊𝑊𝑊 (𝑘𝑘𝑘𝑘)
Basic Density =𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝐺 𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣 (𝑚𝑚3 )Shrinkage =𝐿𝐿𝐿𝐿−𝐿𝐿𝐿𝐿
𝐿𝐿𝐿𝐿

x100%

Where Ls is green dimension;
Lo is oven-dry dimension

Air-drying 147 wood specimens for several weeks. Taking
two pieces from each specimens using sharp shears one by
one during measuring work
Piece 230 mm x 30mm ofsurface area

PithPiece 1

Measurement were performed by a portable
spectrophotometer (NF-555, Nippon Denshoku; UV-3100pc,Shimadzu) with an opening diameter of 8 mm (NF-555) or 10mm (UV-3100pc)with an opening diameter of 10 cm using
CIELab color system; L* (Lightness), a* (redness), b*(yellowness) (Lukmandaru et al., 2009; Moya et al., 2012).

Histograms of heartwood color parameters; L*, a*, b*c. Heartwood color measurement

L*a*b*

2.7. Statistical analysis
Partial correlation analysis• The statistical method for investigating the correlation between
two variables after removing the effects of other variables.
• Helps us to reject spurious correlations (i.e., correlations
explained by the effect of other variables) as well as to findhidden correlations.
• The spearman’s partial rank correlation analysis using R
version 4.0.3 (R core Team, 2020) with ppcor package (Kim,2015) used to investigate the effect of site characteristics afterremoving the effect of stand characteristics.

2.8. Statistical analysis (cont.)
Partial rank correlation network diagram

SABU

SD

Alt

EP

SG

MB

SPBSSF
AP

SiteCharacteristics

PB• The partial rank correlation network diagram
using the qgraph package (Friedman et al.,2011) were used to investigate the effect ofsite characteristics after removing the effectof stand characteristics.
• Circle means a variable.
• Color of circle means type of variable.
• Color and width of line between twovariables means positive (green) or negative(red) correlation and its strength.

3. Results
3.1. Heartwood content
Heartwoodcontent (%)
of basal areaHTHCBDBHTree AgeHeartwood content(%) of commercialvolumeHCV

Slope position
Elevation

Negative

Positive

Partial correlation network between heartwood contents
and topographic conditions. The letter shown in thewhite circles indicate heartwood content of basal area(HCB), heartwood content of commercial volume(HCV), variables of stand characteristics as tree age(TA); stand density (SDe); diameter at breast height(DBH); total height (HT), variables of topographic
conditions as elevation (EV); slope gradient (SG); slope
direction (SD); slope form (SF); slope positions (SP).

3.2 Heartwood properties
Basic density

Tree AgeBD

Stand density
Tangentialshrinkage

DBHTS

Slope gradient
Radial shrinkage

RSElevation
Slope forms

Negative

Positive

Partial correlation network between heartwood properties andtopographic conditions. The letter shown in the circles indicate
variables of heartwood properties as basic density (BD);tangential shrinkage (TS); radial shrinkage (RS), variables ofstand characteristics as tree age (TA); stand density (SDe);diameter at breast height (DBH); total height (HT), variables of
topographic conditions as elevation (EV); slope gradient (SG);slope direction (SD); slope form (SF); slope positions (SP)

3.3 Heartwood color

Heartwood color
parameters

Slope gradientL*

Elevationa*Slope directionb*

Slope forms
Stand density

Negative

Positive

Partial correlation network between heartwood color andtopographic conditions. The letter shown in the circles
indicate variables of heartwood color as lightness (L*);
redness (a*); yellowness (b*), variables of standcharacteristics as tree age (TA); stand density (SDe);diameter at breast height (DBH); total height (HT),variables of topographic conditions as elevation (EV); slope
gradient (SG); slope direction (SD); slope form (SF); slope
positions (SP)Oldertree age

3.4.1. Heartwood content
Luang Prabang’s teak plantation werecommenced to establishing in the lower
site elevation, then expand to higher
elevation; teak tree ages showedsignificant negative correlation withelevation, while slope position waspositive.

Heartwoodcontent ofcommercial
volume (HCV)

LargerSlopeposition

CrestHighUpper

Elevation

3.4. Discussion

MiddleLower
BottomLowLarger

Teak has a faster growth with larger size at bottom site and lower gentle slope (Kolmert,2001; Vaides et al., 2019); due to higher soil moisture content (Watanabe, 2010). Heartwoodcontent increase with tree age and stem diameter (Kokutse et al., 2004), larger-size tree
produced higher heartwood content (Perez et al., 2005). However, Heartwood content had alarger proportion in dry sites than wet sites (Cordero et al., 2003). Those author’s previous
findings were consistent with this present results as shows in right-hand side figure).

3.4.2 Heartwood properties
Basicdensity

Older tree age
Higher stand density

Highheartwoodquality

Low Tangential

Larger- size in DBH

shrinkage

Higher elevation

Radialshrinkage

Lower elevation
Steeper slope
Gentle slope
Concave slope

Tangential and radial shrinkage had mostcorrelated with soil characteristic variables
such as phosphorus, silt content, iron content(Moya et al., 2008).

• Similar results had been reported thatwood basic density had higher athigh stocking plantation, and its
increasing with tree age and stem
diameter (Moya et al., 2003; Perez et al.,
2003; Rizanti et al., 2018).

• However, this study showed standdensity and DBH had no relationshipwith tree age because the teak had
established with narrow spacing withthinning and pruning was uncommon
Our result disagreed with Wanneng etal., 2014 who reported that wooddensity, and shrinkages of different ages
(10 to 25 years old) had no significance,
this may cause by limited wood
samples of 9 trees in their study.

3.4.3 Heartwood color

Site Characteristics

L*Darkera*Redderb*

Yellowish

Southwestern slope
Southeastern slope
Gentle slope
Lower elevation
Straight slope
Lower stand density

Derkyi et al., 2009 reported that environmental factors had a stronger effect on the teakheartwood color than the stand age, especially soil pH decreased moderately with increasing
darkness in Ghana. Moreover, teak heartwood being darker in wetter areas that drier ones. Inaddition, yellowish brown color of heartwood was produced more at drier and fertile sites inCosta Rica (Moya et al., 2012)
In Luang Prabang province, soil pH distributed in flat, gentle and slope area has no significant
differences (Kolmert, 2001). Therefore, present study showed that teak heartwood had adarker at lower elevations might be affect by wet-soil conditions and soil properties.

4. summary
Heartwood content of basal area (HCB) mainly increase with tree size. However,it had slightly affected by topographic conditions. Heartwood content ofcommercial volume (HCV) increase with tree age, having a greater proportion in
middle to upper slope.
Lower shrinkage with higher BD means better wood properties. Therefore, theanalysis results suggest that that teak’s heartwood properties; basic density andtangential shrinkage has an increasing quality with tree age, steeper slope, while
radial shrinkage had a greater quality at gentle concave slope, whereas lower
elevation might be affected by soil condition factors.
Teak heartwood color; Darker color (low L*) associated with the south-west
facing gentle slope in lower elevation. Redder color (high a*) showed arelationship with south-east facing straight slope. Yellowish (high b*) has higher
value at south-west facing slope in lower elevation and lower stand density.

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