Open Journal of Forestry
2013. Vol.3, No.1, 41-48
Published Online January 2013 in SciRes (http://www.scirp.org/journal/ojf) http://dx.doi.org/10.4236/ojf.2013.31007
The Effective Ecological Factors and Vegetation at Koh Chang
Island, Trat Province, Thailand
Nathsuda Pumijumnong, Paramate Payomrat
Faculty of Environment and Resource Studies, Mahidol University, Nakhon Pathom, Thailand
Received October 3rd, 2012; revised November 7th, 2012; accepted November 20th, 2012
This study aims to characterize the tropical rain forest present in the Chang Island, Trat Province, Thailand, and
to analyze the environmental factors to determine its composition and structure. Thirty one plots were sampled,
plant cover was measured in 20 × 40 m2 plots, and the importance value index was calculated. A total of 78 spe-
cies belonging to 32 families were identified.Twenty soil samples were analyzed, and cluster analysis was em-
ployed to classify the vegetation communities. Floristic and environmental data were evaluated and ordered us-
ing canonical correspondence analysis. The results showed that the vegetation communities could be divided
into 4 types and were significantly (p < 0.05) controlled by a secondary distribution according to elevation and
the topographic wetness index (TWI). Mixed plant communities were more likely to distribute in regions with
moderate to low levels of TWI, which were divided by levels of elevation into lowland multi-aged stands (Type
1) or a Calophyllum thorelii Pierre community (Type 2). The Dipterocarpus (Hopea pierrei Heim) community
(Type 3) was more likely to occur in regions with moderate to high levels of TWI, but the result from cluster
analysis showed that some of the plot samples from the Dipterocarpus community were separated by character-
istic importance value index (IVI) values. There was also evidence that the area was impacted by an old distur-
bance created by a rubber plantation. This impact was referred to as a secondary succession community (Type
4).
Keywords: Chang Island; Vegetation Community; Canonical Correspondence Analysis; Ecological
Factors
Introduction
Chang Island is one of only a few islands where a tropical
rain forest is distributed over 70% of the inland area, which has
been preserved in its present form (Environmental Research
Institute, 2007). The island covers an area of 212.947 sq km
and is a major island of the Mu Koh Chang National park in the
Gulf of Thailand, which became Thailand’s 45th National Park
in 1982. During the Pleistocene epoch (Tougard, 2001; Essel-
styn et al., 2009), large sea level fluctuations caused the sea
level to fall by 50 - 150 m, creating land bridge connections.
After this period, the sea level rose and the low-lying regions
were covered with water forming many islands separated from
the mainland. Various fossils have confirmed these events dur-
ing this period (Bird et al., 2005). The research of Chamchum-
roon and Puff provides evidence to support this theory. It is
remarkable that although a large proportion of rubiaceous taxa
show disjunction between Koh Chang and peninsular Thailand,
20% of all rubiaceae taxa recorded from Koh Chang have been
found to be distributed in peninsular Thailand (Chamchum-
roon et al., 2003). This indicates that biological species found
on the mainland may also be found on the Chang islands with a
greater diversity. The tropical rain forest of Chang island has
important roles in storing bioelements and water for local com-
munities and acts as a carbon bank that impacts a large global
area. Since 1902, the records of Schmidt (1900) have shown
that all of the hills of Koh Chang are entirely covered with the
densest jungle. In addition, the Siamese and Chinese popula-
tions scattered along the coasts where the river debouches have
had little influence on the forest cover of the hills. Over the past
century, tropical rain forest areas around the world and in Thai-
land now face loss due to human activities (Royal Forest De-
partment, 1997, 2005). Chang Island is also facing the same
problem as other forest resources and is in danger of losing
forest cover by people focused on acquiring forest land for their
settlements, farms, and plantations. Recently, land use change
caused by tourism had led to construction on the island, in-
cluding business buildings, luxury accommodations, roads, and
harbors. This type of land use changes the ecological system of
Chang Island. Although the Mu Ko Chang National Park was
established at the end of 1982, negative human impact on the
vegetation had already occurred in the more accessible coastal
areas because the settled area of the old communities before the
establishment of the National Park were not included in the pre-
servation. Therefore, some species have become extinct, such
as Ixoradoli chophylla, Lasianthuso ligoneuron and L. schmid-
tii, which according to the reports of Schmidt and Kerr (Cham-
chumroon et al., 2003; Schmidt, 1900), come from the Klong
Nonsi area, a populated area near the Koh Chang District Of-
fice that has no traces of natural vegetation left. None of these
species have ever been identified anywhere else in the Island.
The effect of climate change is another problem because the
area, size, and isolation of Chang Island make it less resilient to
such change.
This study aimed to classify the vegetation communities on
Chang Island and determine environmental factors that influ-
ence their composition and structure. Knowledge of these rela-
tionships may be critically important for planning appropriate
adaptations to climate changes and disturbances due to human
activities.

N. PUMIJUMNONG, P. PAYOMRAT
Materials and Methods
Study Area
The study area is located at Chang Island, Trat Province, in
the southeastern region of Thailand close to the border with
Cambodia. It is located at 132˚51'57"N - 134˚51'57"N and 20˚10'
46"E - 22˚08'89"E. The total area is approximately 212.947
square kilometers. Its length from north to south is 30 kilome-
ters and the width is 14 kilometers. Chang Island is the largest
island in Trat Province. It is close to the Cambodia border,
approximately 300 kilometers southeast of Bangkok. Ninety
percent of the total area is comprised of an extrusive and intru-
sive igneous rock mountain range interchanged with cliffs,
steep hills, and cliffs reaching as high as 743 m above sea level
(ASL), such as the Kao Yai Mountain. The plains along the east
coast of the island are rich in sandy clay and the west coast is
rich in a recent beach deposit (Tansuwan, 2007). Small rivers
and streams on Chang Island are found in areas where the sea
and the creeks meet, flowing through small mangrove forests
around the island, with the exception of a fairly large forest lo-
cated in a protected area on the south coast. The mountain
slopes are covered by dense tropical rainforest forest. The prin-
ciple tree species include Dipterocarpus alatus, D. turbinatus,
Anisoptera costata, Hopea odorata, Irvingia malayana, Podo-
carpus neriifolius, Diospyros spp., Castanopsis spp., Croton
spp., Oncosperma horrida, Caryotamitis., Daemonorops spp.,
Korthalsia grandis, Bauhinia bracteata, Freycinetia sumatrana,
Platycerium coronarium, Amomum spp., Boesenbergia pandu-
rata, and Kaempferia pulchra (Royal Forest Department, 1997,
2005). The climate conditions are influenced by northeast and
southwest Asian monsoons; the former bring dry air to Thai-
land during November through April separated by short periods
of cool (November-February) and hot (March-April) seasons,
and the latter bring moisture from May through October and
account for 90% of the annual rainfall. The mean annual rain-
fall is 4902 mm and total rain fall in some years surpasses 6000
mm (2000 AD, 2006 AD). In addition, the average maximum,
minimum, and mean temperatures are 31.8˚C, 23.6˚C, and
27.4˚C, respectively (Thai Meteorological Department, 2010).
Field Sampling
A quantitative survey of the vegetation was conducted along
the entire topographic gradient of the protected area from North
to South (Figure 1). A total of 31 plot samples were divided
within the 4 survey lines. All samples from the plots were col-
lected in year 2011. A temporary sample plot method was used
in each sample plot. A quadrat of 20 × 40 m2 was set and used
to investigate all tree plants higher than 1.3 m with a diameter
at breast height (DBH) ≥ 4.5 cm. One 4 × 4 m2 quadrat was
used to sample plants with a DBH less than 4.5 cm and higher
than 1.3 m, and one 1 × 1 m2 quadrat was used to analyze
seeding plants shorter than 1.3 m with a DBH less than 4.5 cm.
Elevation, slope, aspect, topographic wetness index (TWI) (Sø-
rensen et al., 2005) were measured in every plots. Twenty soil
samples were randomly collected from 31 plots and correlated
with the aspect and altitude change. For each site, the soil depth
interval to collect samples was 30 cm from the top to a depth of
1 m or until the base rock was reached. These soil samples were
air dried and passed through a 2 mm sieve to remove coarse
gravels, roots, and debris. The soil texture, bulk density, soil
moisture, pH value, soil organic carbon, total nitrogen, avail-
able phosphorus, and exchangeable potassium were subse-
quently analyzed in these samples (Office of Science for Land
Development, 2005).
Data Analysis
A species list was created to further simply identification of
species diversity. We also determined three values for each tree
species in a given community, including the relative density,
relative frequency, and relative dominance (dominance was
defined as the mean basal area per tree times the number of
trees of the species) (Curtis, 1959). The diversity within a com-
munity was calculated using the Shannon-Wiener index (H)
(Hill, 2007). Multivariate analyses were performed on the flo-
ristic data matrices, species, where all species whose impor-
tance value was less than 5% were eliminated. Classification of
plant communities was achieved using a two-way cluster ana-
lysis on the PC-ORD program (Finch, 2005; McCune, 2002).
Thirty-one plots of plant communities were classified based on
the important value of each species in each plot sampled. Ordi-
nation was performed within PC-ORD using canonical corre-
sponded analysis (CCA) (McCune, 2002). CCA is a direct gra-
dient analysis technique that relates community variation (com-
position and abundance) to environmental variation, thereby
providing a determination of significant relationships between
environmental variables and community distribution (terBraak,
1995). CCA axes were evaluated statistically using a Monte
Carlo test. Four topographic variables and 11 soil properties
were used in the CCA.
Figure 1.
Map of Chang Island obtained from a THEOS satellite image. The
green indicates the study area.
42

N. PUMIJUMNONG, P. PAYOMRAT
Results and Discussion
Communities C lass ifi cation
The classification of sub-communities characterized in this
study was different from the classification by the Department of
Forestry (Santhisuk, 2006). At the country scale, the forest area
of Chang Island was defined only as a tropical rainforest of one
of the fourteen sub-communities of Evergreen Forests, based on
three major factors. First, the climatic factor present in East
Thailand is such that the mean annual rainfall is between 1760
and 3140 mm. The number of days of rainfall is between 102
and 150 days, and the total rainfall in some years is more than
4000 mm. When this is compared to the climate of Chang Is-
land (see in 2.1), we can see that the rainfall is clearly higher
than in other parts of Thailand. This is because most areas of
Chang Island are not far from the sea, and steep mountains are
able to capture clouds and cause them to ascend. Second, the
elevation of tropical rainforest is limited to 900 m asl and the
highest peak of Chang Island is 743 m asl. The last factor is the
native natural dominant species, which have developed over a
long period of time into climax stage communities. Cluster
analyses play a substantial role in analyzing the complicated
characteristics of an area that has little change in environmental
gradient. This type of analysis of Chang Island was quite suc-
cessful in identifying distinct vegetation communities in our
study area from the IVI of each species. Four community types
were created with 50.76% - 76.66% of information remaining
in at two-way cluster dendrogram (Figure 2), which indicated a
good pattern in each community. Lowland multi-aged stands
(Type 1) grouped from 6 samples and 60 species of stand trees
in 27 families were recorded, and the IVI of each species was
characterized. The species with IVI > 5% were Tetrameles
nudiflora R. Br. (Tetramelaceae), Hopea pierrei Heim (Dip-
terocarpaceae), Madhuca pierrei Lam (Sapotaceae), Lithocar-
pus ceriferus A. Camus (Fagaceae), and Ficus callosa Willd
(Moraceae). The Shannon-Wiener index for diversity was 5.19
and the absolute density was 1287 tree ha−2. The average tree
height was 13.21 ± 7.28 m, and the average DBH was 47.03 ±
39.36 cm. This community is widely found at lowlands with
moderate slopes and a relatively dry region in TWI. The Calo-
phyllum thorelii Pierre community (Type 2) grouped from 7
samplings and 41 species of stand trees in 22 families was re-
corded, and the IVI of each spices was determined. The species
with IVI > 5% were Calophyllum thorelii Pierre (Guttiferae),
Mesuaferrea Linn(Guttiferae), Hopea pierrei Heim (Diptero-
carpaceae), and Cleistocalyx operculatus Merr and Perry
(Myrtaceae). Guttiferae is a family of tree species that grows
from the coastal plains up to the mountain rain forest, and
Myrtaceae is a major component of the understory layer. The
Shannon-Wiener index for diversity was 4.43 and the absolute
density was 2225 tree ha−2. The average tree height was 12.31 ±
10.51 m, and the average DBH was 35.16 ± 26.06 cm. This
community is widely found at medium to high elevations with
moderate to steep slopes. The Hopea pierrei Heim community
(Type 3) was classified first, with 78.66% of the information
remaining while grouping due to the presence of the dominant
Hopea pierrei Heim stand tree in each sampling (shown as the
dark shade of matrix coding). The eight samples belonging to
this community had 46 species of stand trees in 22 families cha-
racterized by Hopea pierrei Heim (family Dipterocapaceae),
which is widely found in the forest area of Chang Island. How-
ever, the IVI ratio of each species of this community was occu-
pied mainly by Hopea pierrei Heim IVI, rather than others
species (IVI = 114.44 or 38.14%). Dipterocaps are inconspicu-
Figure 2.
Dendrogram derived from two-way cluster analysis of the vegetation data at the study area. Plots
classification showing the indicator species for each division (see species code on Table 2).

N. PUMIJUMNONG, P. PAYOMRAT
us in the Neotropics
mmunities using clus-
a
tandard deviation (SD) of environmental variables for the
types
oand Afrotropics, but are the dominant
trees in the Indomalayan region in most tropical lowland ever-
green forests (Göltenboth et al., 2007). The Shannon-Wiener
index for diversity was 3.96 (high species evenness and rich-
ness) and the absolute density was 1807 tree·ha−2. The average
tree height was 13.72 ± 6.81 m, and the average DBH was
40.97 ± 49.13 cm. This community is widely found at mid ele-
vations with moderate to steep slopes and in relatively wet re-
gions with a high TWI (Table 1). The secondary succession
community(Type 4) emerged as a group from 10 samplings and
41 species of stand trees in 22 families characterized by Hopea
pierrei Heim. Almost all of the species were similar to the
Hopea pierrei Heim community (Type 3), but differed in the
species abundance as defined by the IVI ratio. The Hopea pi-
errei Heim (Dipterocapaceae) abundance decreased from 38.14%
to 20.54% and the Shannon-Wiener index for diversity in-
creased to 4.58. The absolute density was 1782 tree ha−2. The
average tree height was 13.37 ± 7.50 m, and the average DBH
was 40.76 ± 34.65 cm. This community is widely found at low
to medium elevations with flat to moderate slopes and a moder-
ate TWI. Some evidence pointed to a defined stage of secon-
dary succession, including the spreading of death rubber trees
in the sampling plots, interviews from local people, and the lo-
cation of the plots near agriculture areas.
Although the classification of forest co
Tble 1.
Mean (±) s
plots associated with each of the six community type.
Community
Type 1Type 4Type 2 Type 3
Numbef plots r o6 7 8 10
Number of species 60 41 46 41
Table 2.
Recorded species and their Important Value Index (IVI) in each com-
munity type (con.).
IVI
Species
Sp. code Type 1 Type 2 Type 3Type 4
Aglaiata A. r 4.36 1.0361- a cordco 0.
Antidesma bu niu s
Anm 1.
Ars 0.76 -
A 1.
2
1.
0.
3.
Ci
A. bun - 1.3 2.21-
tidesma laurifoliuA. lau 0.75 1.2 - 98
Aquilaria crassna A. cra - 2.54 - -
Archidendron quocense A. quo 7.11 1.16 - 7.09
tocarpus lanceifoliuA. lan - -
zadirachta var. siamensisA. sia 0.85 - 41 -
Baccaurea rami flora B. ram 0.93 .14- -
Barringtonia macrocarpa B. mac 10.63 - - 96
Barringtonia racemosa B. rac 2.26 - 61 -
Bouea var. microphylla B. mic 2.3 513.28
Bridelia affinis B. aff 0.7 1.12.662.9
Brucea javanica B. jav 0.7 - - -
Brucea mollis B. mol 4.18 - - -
alophyllum thoreliC. tho 2.94 58 4.319.5627
C 1. 0.
Ch s
C 8 2 4.
6.
0.1
arallia brachiat aC. bra 4.02 - 3876
Carpinus londoniana C. lon 8.35 8.23 5.7210.41
Caryota bacso ne sis C. bac - - 0.62-
aetocarpus castanocarpuC. cas 3.45 1.09 0.87 2.97
hisocheton siamensisC.sia .2 .232.04 87
Cinnamomum bejolghot a C.bej - 0.97 - -
Cleidion spiciflo rum C. spi 9.64 8.84 14.5712.46
Cleistocalyx operculatus C. ope 32 15.78
S
21 369 32283
Topograss index 0 14
Soim)
O
Total nen (%)
Availappm)
E
Bulk D/cm)
hannon-wiener index 5.19 4.43 3.69 4.48
Elevations (m sal.) 0 ± 574 ± 170 ± 727 ± 13
Slope (˚) 14 ± 919 ± 13 20 ± 1414 ± 9
phic wetne
(TWI)
l depth (c
.5 ± 0.6 .29 ± 1.2 .13 ± 2.51.70 ± 2
83 ± 15 68 ± 29 70 ± 1560 ± 19
rganic matter (%)4.1 ± 0.6 4.6 ± 1.4 3.9 ± 13.6 ± 1.2
pH 4.4 ± 0.5 4.5 ± 0.05 4.3 ± 0.24.2 ± 0.4
itrog0.2 ± 0.1 0.2 ± 0.1 0.2 ± 0.12.1 ± 0.1
CEC (cmol/kg) 8.9 ± 1.9 8.3 ± 1.5 9.4 ± 2.510.1 ± 3.2
ble phosphorus (1.3 ± 1.2 1.8 ± 0.9 1.2 ± 0.71.9 ± 0.7
xchangeable potassium (pmm) 51 ± 21.5 46 ± 16.7 32 ± 16.632 ± 9.3
Exchangeable calcium (pmm) 69 ± 64.6 34 ± 12 18.2 ± 9.416.7 ± 9.0
Exchangeable magnesium
(pmm)
ensity (g3
42 ± 42.6 27 ± 13 14.8 ± 9.616.6 ± 8.6
1.1 ± 0.1 1.0 ± 0.1 1.2 ± 0.21.2 ± 0.2
Sand (%) 50.0 ± 11 58.7 ± 8 52.2 ± 1348.4 ± 12
Silt (%) 18.9 ± 5 14.0 ± 3 16.5 ± 718.7 ± 6
Clay (%) 31 ± 8.3 27 ± 5.6 31 ± 7.432.9 ± 6
13.55 1 4
D
3. 5.13
Dipus
5.
1
7.3
Cratoxylum maingayi C. mai 0.8 1.86 - -
Croton argyratus C. a rg 1.13 4 2.021.1
Dacrydium elatum D. ela - 3.13 - -
iospyros decandra D. dec 0.77 - 0.662.58
Dipterocarpus sp. D. sp 32 2.66 980.4
Dipterocarpus sp. 2 D. sp2 2.61 - - -
terocarpus turbinatD. tur 0.74 - 1.69 -
Elaeocarp us robusus E. rob 0.79 - - -
Eurycoma longifolia E. lon 2.12 6.4 1.4521
Fagraea fragrans F. fra - .49 - -
Ficus callosa F. cal 15.86 1
0.7 -
Gi
G 2 7.9.
2.09 9.5113.1
Firmiana colorata F. col - -
arcinia hanburyG. han 8.1 12.95 6.1111.54
arcinia nigrolineataG. nig 3.29 .018812
Garcinia specio sa G. spe - 7.25 2.661.5
Heritiera javanica H. jav - 2.33 - 0.46
44

N. PUMIJUMNONG, P. PAYOMRAT
Continue
IVI
Species
Sp. code Type 1 Type 2 Type 3Type 4
Hoperei H.iea pier p23.9 530.55 1144.61.36
Horsfieldia irya
Ira
1
L
Lits
H. iry2.28 - - 3.39
avingia malayanI. mal5.17 - - 2.13
Ixora cibdela I. cib 0.7 .17- -
Knema linifolia K. lin2.48 - - -
itchi chinensis L. chi1.47 - - -
hocarpus ceriferuL. cer16.11 6.35 1.3.
1.6.
Lophnum 0.62
Mara
02 56
Lithocarpus sp. L. sp 2.85 - - -
Lithocarpus sp. 2 L. sp24.4 - - -
Litsea pierrei L. pie12.14 2.928396
opetalum duperreaL. dup- - -
dhuca grandifloM. g ra10.75 10.94 8.228.74
Madhuca pier rei M. pie217 7. 111
M
Ms
.4046.93.2
Mangifera caloneura M. cal- - 1.3 2.02
aytenus marcaniiM. mar0.7 1.12 0.64-
Melanorrhoe a usitata. M. usi- - 6.339.54
emecylon garci nioideM. gar5.26 12.46 12.611 6
2.
5.7
Mesua ferrea M. fer013
Oncria
0.96
Sc 2 4.7.
6. 2
2.
S.
Sy
4.7 6.09 1.58
Ochna intege rrima O. int4.25 - - -
osperma tigillaO. tig- - - 2.69
Paeinari anamense P. ana1.5 - - -
Phyllanthus e mblica P. emb- - -
aphium macropodumS. mac7.39 .394191
Semecarpus Sp. S. sp 82.01 5.26-
Shorea hyp ochra S. hyp8.62 9.31 6.42 8.23
Sloanea sigum S. sig- 4.67 2.7867
Spondias bipinnata S. bip2.22 - - -
terculia foetida LS. foe- - 1.22-
zygium diospyrifoliumS. dio0.7 - - -
Tetrameles nudiflora T. nud246 - 1.
1 6.5.
Xerosum 5.
1
2.
0.
.90.7 94
Vatica odorata V. ode- 2.879168
Walsura angul at a W. ang3.57 - 1.952.69
permum noronhianX. nor82 1.01 1.46-
Unknow 1 Uk1 - - - 0.47
Unknow 2 Uk2 1.39 - - -
Unknow 3 Uk3 .2- - -
Unknow 4 Uk4 0.7 - - -
Unknow 5 Uk5 - 32- -
Unknow 6 Uk6 0.78 - 64-
Note: *The for some IVI values indicate I5 (5%or
each community.
ter analyall islands rl(a result ofhe
CCA ordination graph shown in Figure 3), it clearly showed a
d. The eigen-
alysis represent the relative contribu-
tio
gray shading VI values ≥ 1) f
sis on a sm tendto oveap t
difference in the abundance of dominant species. Hopea pierrei
Heim (Dipterocapus) was found in all the communities, includ-
ing the Hopea pierrei Heim community, secondary succession
community, Calophyllum thorelii Pierre community, and low-
land multi-aged stands, but with different IVIs, which were
38.15%, 20.54%, 10.18%, and 7.86%, respectively. A similar
pattern was obtained when a cluster analysis was performed on
the literal evergreen forest of Samesan Island (Payomrat, 2011).
Ordination diagram and species composition of five sub-com-
munity types showed an overlap of Memecylon plebejum,
which is a dominant species between four communities, but
different IVI ratios were observed. However, some studies of
small islands have identified distinct vegetation communities
using cluster analysis. Phra Thong Island has a large alluvial
deposit sand plain with sinking seashore and productive mud-
beaches on estuaries of many long rivers, which is different
than the terrain of Chang Island. This island covers the Cajuput
forest, Cajuput swamp, Peat swamp forest, Beach forest, grass-
lands, and mangroves (Pumijumnong, 2005). Cluster analysis
of the sub-forest community (Thaisatuen, 2010) and Poaceae
and Cyperaceae (Boutrat, 2009) on Phra Thong Island were
successfully classified as communities with 60% - 95% re-
maining information, which is similar to the present study, with
the exception of the grassland type.
Relationshi p be t w e en C ommunities and
Topographic Factors
Elevation and TWI were similarly important factors control-
ling the community distribution of Chang Islan
values in an ordination an
n of each axis to the explanation of the total variation in the
data. The CCA eigenvalues of the 3 two ordination axes were
0.303, 0.253, and 0.172, respectively (Table 3). A Monte Carlo
test confirmed the statistical significance of the axes (P = 0.05).
The first three axes explained 12.5% of the variance in the spe-
cies data. From the Table 4, the highest intraset correlations with
axis 1 was TWI (0.819) and axis 2 was the elevation (−0.858).
Figure 3.
CCA plot ordination with the community types
derived from cluster analysis. Type 1 = lowland
pe 2 = Calophyllum tho - multi-aged stands; Ty
relii Pierre community; Type 3 = Hopea pierrei
Heim community; and Type 4 = secondary
succession community.

N. PUMIJUMNONG, P. PAYOMRAT
Table 3.
Summary s
Axis 1 Axis 2 Axis 3
tatistics table for the CCA ordination.
CCA
Eigenvalues
% of variaxplained 5.4.2.
Cumud
0.
0.303 0.253 0.172
nce e2 3 9
lative % explaine5.2 9.6 12.5
Pearson correlation 981 0.88 0.894
Tabl
Canoniintraset cions oronmental vari-
bles ws of the C
Canonical coefficients Canonical coefficients (intraset)
e 4.
cal coefficients and
ith the first three axe
orrelat
CA.
f envi
a
Variable Axis 1 Axis 2 Axis 3Axis 1 Axis 2Axis 3
TWI 0.299 0.609 0.3110.35 0.819 0.456
Elevation −0.734 0.315 −0.199 −0.858 0.424 −0.291
Slope 0.002 0.29 −0.6290.002 0.39 −0.921
vnb
Fi . Tgthe is proportional to it-
nce and the angle between two vectors reflects the degree of
o
r. (TETRAMELACEAE), Hopea pierrei Heim (DIPTE-
R
g develop-
m
Vectors representing enironmetal variales are shown in
gure 3he len of th vectors impor
ta
crrelation between the variables. The angle between a vector
and each axis is related to its correlation with the axis. Only
variables with a correlation coefficient higher than 0.5 are rep-
resented in order to compare the classification between the
cluster analysis result and CCA ordination. The derived com-
munity types are not clearly separated. Low-land multi-aged
stands (Type 1) and Hopea pierrei Heim community (Type 3)
grouped well on the upper right and lower right, respectively.
The Calophyllum thorelii Pierre community (Type 2) and Sec-
ondary succession community (Type 4) have an overlapping
distribution on the lower to mid-gradient.
TWI, which combines the local upslope contributing area
and slope, is commonly used to quantify the control of hydrol-
ogy, and therefore is used to define local topographic charac-
teristics as a better representation than slope gradient alone.
Many studies have showed a correlation between TWI, soil
moisture, soil water level, ground water level, soil pH, and
vascular plant species richness (Sørensen, 2005; Zinko et al.,
2005; Giesler et al., 1998). Relative wetness in TWI tends to
increase the richness in species and diversity. A comparison of
TWI of the communities, species richness, and species diversity
in this study showed that relative TWI tended to have a positive
correlation with species richness (number of species)in three
communities on the sloping area (Calophyllum thorelii Pierre
community Type 2, Hopeapierrei Heim community Type 3,
and secondary succession community Type 4). However, a ne-
gative correlation with species was observed. The community
with the highest diversity and species richness, lowland multi-
aged stands (Type 1), did not depend on the TWI value. This
community is located on the flatland near the foot hill where
the deepest soil affected the distribution of old trees with multi-
layered strata. Soil moisture and humidity in the understory are
high and much more stable compared to the canopy. TWI had a
negative correlation with species diversity because of the suc-
cess of Hopea pierrei Heim in the wetness area succession. As
shown in Figure 4, Hopeapierrei Heim was highly responsive
to TWI, so much so that the others species had a reduced prior-
ity and the Shannon-Wiener index was decreased (Tables 1 and
2).
We selected key species by choosing species with an IVI
value ≥15 or 5% from each community. Four species from the
lowland multi-aged stands (Type 1) were Tetrameles nudiflora
R. B
OCARPACEAE) Madhuca pierrei Lam (SAPOTACEAE),
Lithocarpus ceriferus A. Camus (FAGACEAE), and Ficus cal-
losa Willd (MORACEAE). Four species from the Calophyllum
thorelii Pierre community (Type 2) were Calophyllum thorelii
Pierre (GUTTIFERAE), Mesua ferrea Linn. (GUTTIFERAE),
Hopea pierrei Heim (DIPTEROCARPACEAE), and Cleisto-
calyx operculatus Merr. and Perry (MYRTACEAE). Two spe-
cies from the Hopea pierrei Heim community (Type 3) were
Hopea pierrei Heim (DIPTEROCARPACEAE) and Cleistoca-
lyx operculatus Merr. and Perry (MYRTACEAE). Four species
from the secondary succession community (Type 4) were Ho-
pea pierrei Heim (DIPTEROCARPACEAE), Calophyllum tho-
relii Pierre (GUTTIFERAE), Cleistocalyx operculatus Merr.
and Perry (MYRTACEAE), and Memecylon garcinioides Bl.
(MEMECYLACEAE). The IVI values of each species are
shown in Table 2. A fit response curve created a turnover point
of communities responding with TWI. Low land multi-aged
stands (Type 1) and some species from the Calophyllum tho-
relii Pierre community (Type 2) occupied relative dry in TWI
and turnover to Dipterocapus community (Type 3, 4) and Calo-
phyllum thorelii Pierre community (Type 2) when TWI higher
than 2, as defined by a moderate level of Hopea pierrei Heim
abundance (key species of Type 3, 4) and Cleistocalyxo percu-
latus Merr. and Perry (key species of Type 2). However, the
assumption of a high value of TWI occurred with the appear-
ance of a creek based on field survey (TWI > 5), even if some
of species, such as Hopea pierrei Heim, Ficus callosa Willd,
and Tetrameles nud i f l or a R. Br. occupied this area.
Dipterocapace (Hopea pierrei Heim) were successfully dis-
tributed along all environmental gradients of Chang Island and
were found in all strata. A characteristic feature of these plants
is the amount of sunlight that can be tolerated durin
ent. An emergent dipterocarp has a crown that receives full
sunlight during the entire day, whereas as a seedling, it not only
requires tolerant shade, but it will die when subjected to full
sunlight during the entire day (Göltenboth, 2007). Thus, clear
cutting of the forest will be a serious problem for dipterocarp,
as seedlings will have less of a chance to survive. Buttress roots
Figure 4.
Fit response curves between key species and TWI (the species codesare
show in Table 2).
46

N. PUMIJUMNONG, P. PAYOMRAT
are another characteristic feature of dipterocarp (common name
of Hopea pierrei Heim is TaKhianRak; “Rak” means root in
Thai). It occurs when trees with a shallow root system prevail
in areas where nutrient concentrations are largest near the soil
surface or stand against a steep slope. Why these structure are
formed is still not fully understood, as research has shown that
buttresses do not increase the trees’ resistance to mechanical
stress, such as trunk snapping, or alleviate the pulling strain on
the roots (Richard, 1996).
Elevation was positively correlated with tree density (r =
0.979). The Calophyllum thorelii Pierre community (Type 2),
which was distributed along the high land until the peak, had
t tree density (2225 tree·ha−1), whereas the tree den-
unity (Type 4), and low land multi-aged
2), and low land multi-aged stands
(T
u-
nity Type 2 (5300.04 ha or 30.41%), Hopea pierrei Heim com-
a or 13.53%), secondary succession
community
the highes
sity of the Hopea pierrei Heim community (Type 3), secondary
succession comm
stands (Type 1) were 1807, 1782, and 1287 tree ha−1, respec-
tively. This relation pattern is seen in the tropical rainforest of
Phukhet Island as well (Kiratiprayoon, 1986). Normally, high
density leads to a high percentage of basal area, but the basal
area of Chang Island was not increased. TWI showed a posi-
tive correlation with the basal area in this study (r = 0.928). The
average TWI of Hopea pierrei Heim community (Type 3), se-
condary succession community (Type 4), Calophyllum thorelii
Pierre community (Type
ype 1) was 4.13 ± 2.36, 1.70 ± 1.95, 1.29 ± 1.16, and 0.5 ±
0.55, respectively, while the percentage of basal area was
0.5886%, 0.4056%, 0.3396%, and 0.3845%, respectively. Many
studies have shown the same results as our study, where mois-
ture is a factor that can potentially control the above ground
biomass in 6 forest types of Thailand: tropical evergreen rain
forest, seasonal rain forest, lower mountain coniferous forest,
upper mountain rain forest, mixed deciduous forest, and de-
ciduous dipterocarp forest (Working group I: Scientific Basis of
Climate Change, 2011; Rueangruea, 2009; Sunthisuk, 2006;
Kiratiprayoon, 1986). Species response curve with regard to
elevation showed six key species responding in three patterns
(Figure 5). The Hopea pierrei Heim curve primarily showed a
bell-shape curve (abundant at mid-elevation), which intersected
the Calophyllum thorelii Pierre curve at an elevation at 550 m
asl. It can be concluded that the Dipterocarpus (Hopea pierrei
Heim) community tends to turnover to the Calophyllum thorelii
Pierre community at elevations greater than 550 m asl, and
turnover to the secondary succession community (Type 4) at
low elevation with an increase of Memecylon garcinioides Bl.,
which is the other key species of this community. The response
curve of Madhuca pierrei Lam and Tetrameles nudiflora R. Br.,
which are key species of lowland multi-aged stands (Type1),
showed a negative correlation with elevation. A positive corre-
lation of the Mesua ferrea Linn curve (key species of Calo-
phyllum thorelii Pierre community, Type 2) intersected the
Madhuca pierrei Lam curve at an elevation of 250 m asl.
Moreover, the decrease of Hopea pierrei Heim at a low eleva-
tion suggests that the limit of distribution of lowland multi-aged
stands (Type1) is 250 m asl. Lithocarpus ceriferus A. Camus,
Cleistocalyx operculatus Merr. and Perry, and Ficus callosa
Willd were excluded because these species did not respond to a
change in elevation (the curves ran parallel with the x-axis).
Area of Community
Based on the fit respond curve for elevation and TWI, we
conclude that the environmental conditions of each community
are as follows: Lowland multi-aged stands (Type 1): Elevation
< 250 m asl and TWI < 2, Calophyllum thorelii Pierre commu-
nity (Type 2): Elevation > 250 m asl and TWI < 5, Hopea pi-
errei Heim community (Type 3): 250 < Elevation < 550 m asl
and 2 < TWI < 5, Secondary succession community (Type 4):
Elevation < 550 asl and 2 < TWI < 5 and Creek representation:
All elevation gradient and TWI > 5.
From the Figure 6, the total forest area was 17428.45 ha,
which was comprised of low land multi-aged stands Type 1
(4807.99 ha or 27.59%), Calophyllum thorelii Pierre comm
munity Type 3 (2358.54 h
Type 4 (3731.24 ha or 21.41%), and creek area
(1230.65 ha or 7.06%). Some areas of the secondary succession
community were complicated. These areas were composed of
Figure 5.
Fit response curves between key species and elevation (the species
Table 2c odes are shown in ).
Figure 6.
Area of four community types (Type 1-4) and creek.

N. PUMIJUMNONG, P. PAYOMRAT
48
two probable communities: the natural Dipterocarpus commu-
nity and secondary succession community, because one of the
factors controlling the secondary succession community was
human disturbance. Therefore, it was not included in this study.
Conclusion
Chang Island has a particularly high evenness and richness of
species. We investigated an area of 2.48 ha and recorde total of
78 species from a total of 32 families. Two-way cluster analysis
classified the tropical rain forest into four sub-communities:
lowland multi-aged stands (Type 1), Calophyllum thorelii Pi-
erre community (Type 2), Hopea pierrei Heim community
(Type 3), and secondary succession community (Type 4). Ele-
vation and the topographic wetness index (TWI) affected the
distribution of each community. Lowland multi-age stands,
which had the highest diversity and richness, correlated with
low elevation and relatively low TWI or dry conditions. The
Calophyllum thorelii Pierre community had the highest tree
density and correlated with high elevation and relative moder-
ate to dry TWI conditions. The Hopea pierrei Heim community
had the highest percentage of basal area and the lowest diver-
sity, and was extensively covered by the Hopea pierrei Heim
species. It correlated with a mid-elevation near creeks and had
relatively wet TWI conditions. Finally, the secondary succes-
sion community (Type 4) was related to mid to low elevation
and relatively moderate to wet TWI conditions.
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