CHANGES IN THE SPECIES COMPOSITION, STAND
STRUCTURE AND ABOVEGROUND BIOMASS OF A LOWLAND
DIPTEROCARP FOREST IN SAMBOJA,
, Djoko Wahjono
and Rinaldi Imanuddin
over a 4.3-yr period (December 2004 – April 2009) in a lowland dipterocarp forest of Samboja,
East Kalimantan. This study was conducted in six permanent sample plots (100 m x 100 m each)
distributed over an area of 26.5 ha of Samboja Research Forest. All woody plants ≥ 10 cm dbh
(diameter at 1.3 m aboveground) were identified. In December 2004, 2.143 trees were measured
in the six plots, consisting of 39 families, 82 genera and 111 species. The condition in April 2009
(after 4.3 yr) was: 2,466 trees, 40 families, 86 genera and 123 species. Most species were found
in both occasions. Fourteen new species were registered, which contributed to 9.8% of a net
addition of the total number of species found in the six plots. Over the 4.3-yr period, there was
also an increase of 15.1% in density, 12.9% in basal area, and 11.6% in aboveground biomass,
respectively. The density increased from 357 to 411 trees per ha; the basal area increased from
20.09 to 22.67 m
; and the aboveground biomass increased from 286.3 to 319.4 ton ha
followed by Euphorbiaceae, Burseraceae, Fabaceae, and Anacardiaceae (more than five species).
Most genera (80%) contained just one species, but Shorea with 13 species was the richest. Four
families (Dipterocarpaceae, Fabaceae, Myrtaceae and Lauraceae) contained more than 80% of
the aboveground biomass in both occasions (75% of them from Dipterocarpaceae family). The
increases in species richness and density
did not cause any significant differences in the diversity
index and diameter distribution. This condition suggested that forest vegetation of the study site
maintains its diversity composition and structural features over the period of study.
Keywords: stand dynamic, structure, biomass, permanent plots, tropical forest
Sustainable forest management is an important issue in Indonesia. Sound forest
management cannot possibly be applied without an understanding of the basic ecology
of the forests. One prerequisite for sustainable forest management is reliable information
Center for Forest Conservation and Rehabilitation Research and Development, Forestry Research and
Corresponding Author. E-mail: firstname.lastname@example.org
Center for Forest Productivity Improvement, Forestry Research and Development Agency
Jl. Gunung Batu No. 5 Bogor, Indonesia.
will grow and respond to natural conditions or occasional disturbances. However, little
information is available regarding the dynamics of species composition, structural and
productivity (biomass) changes of the tropical forests in Indonesia over time.
Most studies in Indonesia are based on surveys on compositional and structural
patterns of certain sites or forests at one occasion (e.g. Kartawinata
et al., 1981; Riswan,
1987; Suselo and Riswan, 1987; Sist and Saridan, 1998; Heriyanto, 2001; Krisnawati,
2003). Forest vegetations, however, are dynamic and changes occur continuously at
individual and species population levels throughout time, eventhough the vegetation
as a whole is expected to be stable, as a result of a balance between growth, recruitment
and mortality. Several studies on forest dynamics in other tropical regions have been
conducted (e.g. Lieberman
et al., 1985; Manokaran and Kochummen, 1987; Swaine et
al., 1987); however, a better understanding of the tropical forest dynamics particularly
in Indonesian forests is still limited. Measurement of permanent sample plots at certain
intervals and over a long period is therefore required for understanding of the process in
which the changes occur at individual, species and stand or community levels.
The objective of this study was to analyse the changes in species composition, stand
structure, and aboveground biomass of the woody plants of a lowland dipterocarp forest
in the Samboja Research Forest, East Kalimantan, over a period of time (December
2004 - April 2009). The results were expected to provide an insight whether the forest
vegetation in the study site would maintain its species composition and structural
characteristics over the period of time.
II. MATERIALS AND METHODS
A. Site Description
This study was conducted in the 26.5 ha of 504 ha remaining Samboja Research
Forest, 4.5 km from the starting point of Samboja-Semoi route (0°59’ N latitude
and 116.56° E longitude, Figure 1). This unlogged natural forest was considered as a
miniature of tropical rain forest in Kalimantan due to its high biodiversity (Gunawan
et al., 2007). About 296 species of 54 families including species of Palmae have been
reported to inhabit this forest (Yassir and Juliati, 2003).
The site is located at the village of Sungai Merdeka, the Sub-District of Samboja,
District of Kutai Kartanegara, East Kalimantan Province. The average annual
precipitation in the site ranges from 1,682 to 2,314 mm with the number of rainy days
of 72–154 days per year. The average temperature is about 26–28
C with the minimum
C and the maximum value in the night time of 32.7
et al., 2006; Atmoko, 2007).
The altitudinal range of the area is from 40 to 150 m above sea level. The topography
is relatively undulating and rolling with the slopes of around 10–40% while some parts
may reach 60% (Gunawan
is typically quite acidic and deficient in major nutrients, such as calcium and potassium.
Geologically, the soil is mostly derived from tertiary sedimentary rocks.
The study was based on the results of the monitoring of six permanent sample plots
(100 m x100 m square plot of 1 ha each; Figure 1) distributed over an area of 26.5 ha of
Samboja Research Forest. All plots were first delineated on the ground to cover the range
of topography of the site. Each plot was divided into 100 sub-plots (quadrats) of 10 m x
10 m to allow a better control of measurement and monitoring. The plot establishment
and the first measurement were conducted in December 2004 and then re-measured in
May 2006, June 2008, and April 2009 (in total 4 measurements). However, only the first
and fourth measurements covering a period of 4 years and 4 months (approximately 4.3
years) were reported in the present study.
In each plot, all woody plants of at least 10 cm dbh (diameter at 1.3 m aboveground)
were marked, identified and measured.
The dbh of every target tree was measured at
each measurement, and dead and newly recruited target trees were registered at each
re-measurement time. Tree height was measured by using a hagameter for all trees in
the plots for the first and second measurements and 100 trees with various dbh (one
Figure 1. Location of the research plots in Samboja Research Forest, East Kalimantan
mapped, but no analysis was done at the individual level.
All tree specimens were collected and identified in the herbarium collection of the
Samboja Forestry Research Institute. A list of species was compiled at each measurement.
Shannon's diversity and Pielou's evenness indices were calculated for each occasion
(Magurran, 1988; Ludwig and Reynolds, 1988). Stand density (number of trees), basal
area, and aboveground biomass were also calculated at each occasion (Husch
et al. (1986) for undisturbed tropical lowland rain forests in Sebulu, East
Kalimantan province. The site of their study was considered to have similar characteristics
with this study site in terms of forest type, topography, climate, soil type, and dominant
family in the forests.
Changes in the species composition, stand density, basal area,
and aboveground biomass were analysed and then compared at each assessment.
differences of diameter distribution between the two occasions were also tested using a
III. RESULTS AND DISCUSSION
A. Species Composition
In December 2004 2,143 trees of ≥ 10 cm in diameter were measured in six
permanent sample plots of the Samboja Research Forest. They consisted of 39 families,
82 genera and 111 species. The condition in April 2009 (after 4.3 yr) was: 2466 trees, 40
families, 86 genera and 123 species. The list of species and families found in these plots
for both measurement times was presented in Appendix 1.
Most species were found in both occasions (2004 and 2009), except for
nervosa and Trigonostemon laevigatus that did not occur in 2009, although these species
might still be present below the diameter limit (10 cm) used in this study. Fourteen new
species were registered (i.e.
Actinodaphne malaccensis, Albizia minahasae, Diospyros
confertifolia, Durio oxleyanus, Knema conferta, Magnolia borneensis, Palaquium
pseudorostratum, Palaquiun gutta, Parishia insignis, Porterandia anisophylla, Dillenia sp.,
Durio sp. Parashorea sp., and Shorea sp.1), which contributed to 9.8% of a net addition
of the total number of species found in the study site over the 4.3-yr period.
The species that disappeared from the plots occurred at low density in the study
area (less than one tree per ha) and any cause of mortality might eliminate them from
the plots. However, their absence might be replaced by newly recruited trees due to
ingrowth. These species might have also been represented in the study site as smaller
individuals. The same state applied to the new species that entered the plots.
The Dipterocarpaceae family was the richest in species (more than 20 species
found in both 2004 and 2009), followed by the families of Euphorbiaceae, Burseraceae,
Fabaceae, and Myrtaceae (more than five species found in both occasions) (Figure 2).
consisting of 13 species.
The indices of Shannon’s diversity and Pielou's evenness were 3.34 and 0.71 in 2004,
respectively; and 3.33 and 0.69 in 2009. Result of statistical
t-test (Zarr, 2006) indicated
that these values were not different (
P < 0.05) meaning that the changes in species
richness over the period of 4.3-yr did not cause any difference in the value of Shannon 's
diversity index, which is little affected by rare species. Approximately 70% of the species
found in the plots were rare species (low density) with only less than one tree (dbh ≥ 10
cm) per ha. However, this low density of the species is typically found in tropical rain
density, the forest state in the study area can still be
considered to be
stable, as the value
of Shannon's diversity index is above 3.0 (Odum, 1971). This result
suggested that the
vegetation of the study site maintains its original composition.
B. Stand Structure
In the first measurement (December 2004), 15 species comprised about 80% of the
stand basal area (
BA) and 77% of the stand density (N) over 10 cm dbh (Table 1). All of
Dipterocarpaceae family which contributes to 44% of the stand density and 53% of the
basal area. Most of them are fast growing and shade tolerant. The most abundant species
After the 4.3 yr period, the same species still comprised 80% of the stand basal area
but the ranking changed slightly (Table 1).
Shorea bracteolata ranked fifth in basal area
Eusideroxylon zwageri), since more recruited trees of this species entered
the plots. However, in terms of stand density the ranking retained the same. A study
conducted by Silva
et al. (1995) in the logged-over area of the Tapajós Forest, Brazil,
found a slight change in species ranking; but another study, conducted in the same site
of the Brazilian Amazon (Carvalho, 1992, cited
in Silva et al., 1995), found no major
changes in species ranking before and after logging.
In general, the stand density in the study site increased by 15.1% from 357 trees
per ha to 411 trees per ha over the 4.3 yr period. Similarly, the basal area increased by
12.9% from 20.09 m
to 22.67 m
. The same trends applied to all individual plots
ranging from 5.8 to 24.5% in density and from 9.8 to 17.7% in basal area. The positive
changes in density found in this study probably due to more species and more recruited
trees entered the plots. The number of trees that pass the minimum diameter limit was
about 71 trees per ha over 4.3 yr (or 16 trees ha
), while the mortality was lower
(about 17 trees per ha over 4.3 yr or 4 trees ha
). The loss of basal area by death of
some trees was lower than the gain by growth of surviving trees. Most of species showed
a positive balance in basal area (Table 1).
Compared with other studies conducted in several other topical forests, the change
or the increase found in this study was greater which was probably due to an increase
in the number of recruited trees and the fast growth of some species (particularly from
Dipterocarpaceae family). Felfili (1995) reported a reduction of 2% in density over 5 cm
dbh for a 6-yr period for a gallery forest located in the Central Brazil. Another study by
over a 9-yr period. On the other hand, Silva
et al. (1995) found an addition of 13% in
density for a 11-yr period for a logged-over forest also located in Brazil. The increase in
density was also reported by Carvalho (1992), cited in Silva
et al. (1995), who found
an addition of 1% for an Amazonian site over 8-yr period. Several other studies in
Malaysian dipterocarp forest (Manokaran and Kochumen, 1987) and in Ghana forest
et al. 1987) showed smaller variation in density over the study period than in
this study (Table 1).
The addition (due to recruitment) and reduction (due to mortality) in the number
of trees coupled with the growth of trees at a site would result in balance vegetation.
Felfili (1995) noted that if there is a period of high mortality (when the density is
reduced) and followed by another period of high recruitment (when new trees fill the
gaps formed previously), the stand state can be said to reach the dynamic equilibrium,
Table 1. Changes in stand density (
N) and basal area (BA) of the six permanent
plots in the Samboja Research Forest, East Kalimantan
(December 2004-April 2009) listed based on basal area
N = number of trees per ha; BA = basal area (m
Mor = number of dead trees per ha; + = increase; - = decrease
and April 2009 (Figure 3), showed a reversed-J shape which indicated a continuous
ingrowth. The same trends applied to other diameter distributions for other years.
For dead trees, numbers of mortality tend to decrease with increasing diameter. The
diameter distributions showed that the number of trees at each diameter class generally
increased over 4.3 yr period. However, the differences were not significant between the
two occasions; the test statistic of the Kolmogorov-Smirnov two sample test (K-S) was
0.0062. The distributions between 2004 and other years (2006 and 2008) were also not
significantly different (K-S of 2004-2006 = 0.0179; K-S of 2004-2008 = 0.0056). The
same results were found by e.g. Swaine
et al. (1987) for moist semi-deciduous forest
in Kade, Ghana over a 14 yr period and Felfili
et al. (2000) for savanna woodland in
Brazilian Amazon over a 9 yr period.
C. Aboveground Biomass
Four families (Dipterocarpaceae, Fabaceae, Myrtaceae and Lauraceae) contained
more than 80% of the aboveground biomass (≥ 10cm dbh) in both 2004 and 2009
(Table 2). Of these, almost 75% of them were
from Dipterocarpaceae family which
comprised about 43% of the total aboveground biomass contained in the plots. The
Diameter class (cm)
Figure 3. Diameter distribution of the six permanent plots in the Samboja Research Forest
highest value in the amount of aboveground biomass
Sindora wallichii and Shorea bracteolata. These three species contributed to
a net addition of 30% of total aboveground biomass.
Table 2. Changes in aboveground biomass (
AGB) of the six permanent plots in
the Samboja Research Forest, East Kalimantan (December 2004-April
Overall, the aboveground biomass of all species in the plots increased by 11.6%
(33.1 tons ha
) over the 4.3 yr period, i.e. from 286.3 tons ha
in December 2004 to
319.4 tons ha
in April 2009 (Table 2). The same trends were also observed for each
The trend of aboveground biomass increases may be attributed to the high rate of
over the 4.3 yr was not significantly different. No significant change was found in the
biomass with time. Most of families showed smaller change (less than 1 tons
by these families was limited over the 4.3 yr period.
The number of species, stand density, basal area and aboveground biomass of the
woody plants ≥10 cm dbh increased over 4.3 yr. The changes in stand density and basal
area in the Samboja Research Forest were greater than those found in several other
tropical forests. These increases were probably due to more species entered the plots and
more recruited trees passing the minimum diameter limit used in this study in addition
to the fast growth of some species growing in the plots.
The increases in species richness and density, however,
did not cause any significant
differentiation in the diversity index and diameter distribution, respectively. This
condition suggested that forest vegetation of the study site maintains its diversity
composition and structural features over the period of study.
with regular measurements, however, is necessary to clarify these trends.
We are grateful to the Center for Forest Conservation and Rehabilitation Research
and Development (formerly Center for Forest and Nature Conservation Research and
Development), Forestry Research and Development Agency of Indonesia for providing
financial support to conduct this research. Thanks are also due to the Samboja Forestry
Research Institute for providing us with the necessary research supports during our
fieldworks and the herbarium staff for identification of the collected plant materials.
Our technicians and local field crew from Samboja were thanked for assisting us in
the field measurements. Part of this study was presented at the International Annual
Meeting of the Association for Tropical Biology and Conservation, 19-23 July 2010,
Sanur, Bali (Indonesia).
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APPENDIX 1. List of species and families found in the six permanent plots of
Year of Measurement
Appendix 1 (continued)