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B I O D I V E R S I T A S
ISSN: 1412-033X
Volume 17, Number 1, April 2016 E-ISSN: 2085-4722
Pages: 96-101 DOI: 10.13057/biodiv/d170114
Proof of Acacia nilotica stand expansion in Bekol Savanna, Baluran
National Park, East Java, Indonesia through remote sensing and field
observations
SUTOMO
1,2,♥
, EDDIE VAN ETTEN
2
, LUTHFI WAHAB
3
1
Eka Karya Bali Botanical Garden, Indonesian Institute of Sciences (LIPI), Candikuning, Baturiti, Tabanan 82191, Bali, Indonesia. Tel. +62-368-
2033211,
♥
email: sutomo.uwa@gmail.com
2
School of Natural Sciences, Edith Cowan University, Joondalup Drive, Perth Western Australia
3
Postgraduate Studies, Faculty of Geography, Gadjah Mada University, Bulaksumur, Yogyakarta 55281, Indonesia
Manuscript received: 17 December 2015. Revision accepted: 12 February 2016.
Abstract. Sutomo, van Etten E, Wahab L. 2016. Proof of Acacia nilotica stand expansion in Bekol Savanna, Baluran National Park,
East Java, Indonesia through remote sensing and field observations. Biodiversitas 17: 96-101. One of woody species that is known to
inhabit certain savanna ecosystems is Acacia nilotica. The Acacia nilotica tree is widespread in the northern savannah regions, and its
range extends from Mali to Sudan and Egypt. Acacia nilotica was first introduced to Java Island in 1850. It then spread to Bali, East
Nusa Tenggara, Timor and Papua. Found in grasslands, savanna is reported as important colonizer at Baluran National Park in East Java
and Wasur National Park Papua. We conducted Vegetation analysis in three areas of the Baluran Savanna namely: Grazed, burned and
unburnt. Our observation result analysis showed that in terms of the three most important tree species in all of the sites that we sampled
(grazed, burnt and unburnt savannas) Acacia nilotica appeared in each of these sites. The values however, vary between sites. Acacia
nilotica Importance Value Index is highest in the unburnt savanna, with IVI reaching almost 250. The unburnt site is actually a burnt site
but with moderate age or time since fire (approximately 6-7 years), whereas the burnt site is savanna with relatively young age/time
since fire (few months to 1 year). We also conducted GIS analysis using Satellite Images (October 2013 and October 2014) to pick up
changes in Bekol savanna. Result showed that expansion of A. nilotica stand occurred towards the savanna. Over dominance of the
woody species A. nilotica could shift the savanna into another ecosystem state, i.e. secondary forest.
Keywords: Acacia nilotica, Baluran National Park, expansion, remote sensing, vegetation analysis
INTRODUCTION
Before the year 1928, A.H. Loe de Boer, from the
Dutch Colonial, had areas of agriculture concession at
Labuhan Merak and Mount Mesigit, Baluran. Since then,
he had always interested in big mammals and thought that
the areas will play important roles in conserving these
animals. Following Indonesia independence, the Ministry
of Agriculture also stated Baluran as game reserve area
with decree No. SK/II/1962. Later on in 1980, the area then
stated as a national park, the Baluran National Park with an
areas of 25,000 ha. Baluran is known for its vast areas of
savanna and is famous as the “Africa van Java” (Baluran
National Park 2010).
Savanna is a term to define ecosystem in tropical and
subtropical that typical of displaying a continuous
herbaceous cover of C
4
grasses that has different patterns
based on seasonality in which it is related to water, and
where woody plants are also of important values but with
sparse patterns and no closed canopy (Frost et al. 1986).
Tropical savannas cover over 20% of the Earth surface,
with the largest coverage is in Africa, Australia and South
America, and just only approximately 10% occur in India
and Southeast Asia (Bond and Wilgen 1996; Werner 1991).
Other savannas ecosystem have also been intensively
studied such as eucalypt savanna woodlands in Northern
Australia (Burrows et al. 1991; Werner 1991), and the
Miombo woodland of Southern Africa (Isango 2007).
Indonesian savanna however remain somewhat unfamiliar
to the scholarly with very few studies have been done. One
of the foremost early studies on Indonesian flora was of
Backer and van den Brink (1963) and van Steenis (1972).
Mountain flora of Indonesia especially in Java Island was
what van Steenis specialized. In his report, even in early
1900, grasslands on Java Mountains are already common.
Fire, according to van Steenis (1972) was presumed as the
major factor that drive the existence of grasslands on Java
mountains especially in East Java which is subject to dryer
dry season, lower precipitation compare to other parts of
the island.
One of woody species that is known to inhabit certain
savanna ecosystem is Acacia nilotica (Figure 1). Acacia
nilotica is known to be abundant originally in Africa
(Brenan 1983) and has been scantly studied. In a study by
Skowno (1999) in Hluhluwe Game Reserve, South African
savanna, A. nilotica was described in terms of their
quantitative structure and distribution. In Australia, this
species is dominant in Queensland where it has been
declared as weeds, and only a few are found in Western
Australia, New South Wales, Adelaide and Northern
Territory (Reynolds and Carter 1990). In Australian
savanna ecosystem’s study by Radford (2001), A. nilotica
SUTOMO et al. – Acacia nilotica stand expansion in Baluran National Park, Indonesia
97
Figure 1. Sketch of Acacia nilotica subsp. indica from Baluran
National Park (Illustrated by M. Sumerta, Bali Botanical Garden,
Indonesia)
is acknowledged to have negative impacts on savannas. A.
nilotica can be threatening to savannas as its adult trees are
apparently fire tolerant and can form thorny thicket
formation (Burrows et al. 1991).
Baluran savanna has also been introduced with the A.
nilotica in the late 1960, where its original purpose was to
create fire break to prevent fire to spread from Baluran
Savanna to the adjacent teak forest. However today A.
nilotica has spread rapidly and threatening the existence of
Baluran Savanna and it has been observed to cause changes
in ecosystem from open savannas to some extent a closed
canopy of A. nilotica in some areas (Barata 2000; Djufri
2004). This condition could put large mammals of Baluran
savanna such as barking deer (Muntiacus muntjak), sambar
deer (Cervus unicolor) and banteng (Bos javanicus) in
endangered due to the loss of browsing and grazing fields
(Sabarno 2002).
This research objective are to provide up-dated
information regarding the state of this exotic species A.
nilotica in Bekol Savanna Baluran National Park and
search for evidences of expansion of A. nilotica stand at the
Bekol Savanna through field observation and Geographical
Information System (GIS) application.
MATERIALS AND METHODS
Baluran National Park located in Banyuputih sub-
District, belongs to Situbondo District in East Java
Province, Indonesia (Coordinates: 7°50′S 114°22′E).
Baluran National Park borders are adjacent to: On the north
it is bordered with Madura Strait, on the east is Bali Strait,
on the south is Bajulmati River, Wonorejo Village and on
the west is with Klokoran River, Sumberanyar Village. The
park is a rough circle, with the extinct volcano, Baluran, at
its center. Baluran has a relatively dry climate and mainly
consists of savanna (40%), as well as lowland forests,
mangrove forests and hills, with Mount Baluran (1,247m)
as its highest peak. According to Schmidt and Fergusson
classification, Baluran National Park (BNP) has type F dry
climate with temperature ranging 27.2-30.9ºC, relative
humidity 77%, and wind speed average 7 knots. Rainy
season in November to April, dry season is in April to
October. Highest precipitation usually is in December to
January. Baluran savanna has alluvial soil type. In dry
season or drought the soil will crack and the deep of the
crack could reach up to 80 cm.
We used vegetation analysis method by using quadrate
plot to sample vegetation following Kent (2011) as seen in
the Figure 2. Quantitative information including above-
ground biomass and floristic composition obtained from
each sites namely: burned, unburnt and grazed. Each site
we created 10 plots for observation and so in total there
were 30 plots all together, randomly located. All plant
species in each plot identified (Indriyanto 2006). Field
herbarium created so that the plants can be more easily
recognized to species level in the subsequent field work,
which demands rapid identification in the field. The
identification assisted by Herbarium Baliensis of the
Indonesian Institute of Sciences. Plant identification also
make used of flora books such as Backer and Bakhuizen
van den Brink (1963), van Steenis (1972), Soerjani et al.
(1986), and Whitten et al. (1996). A diagram profile was
also created by using a transect with 60 m long and 7 m
wide and captured the woody habitus as well as sapling,
seedling and grasses in the boundary area between the A.
nilotica stand and the Bekol Savanna of Baluran National
Park. Vegetation analysis was then conducted to calculate
the value of Important Index (IVI) for tree habitus.
Ordination analysis for tree species composition in the
sampling plots was conducted using Non metric
Multidimensional Scaling (NMDS) in the PRIMER V.5
Software (Clarke and Gorley 2005).
Figure 2. Shape and size of sampling plot (Kent and Coker 1992),
20 x 20 m
2
to observe and measure woody sapling and basal area.
1 x 1 m
2
to observe non woody species and 25 x 25 cm
2
for their biomass
B I O D I V E R S I T A S
17 (1): 96-101, April 2016
98
Satellite images of the Bekol savanna in 2013 were
obtained online using Universal Map Downloader (UMD)
with highest level of pixel category to allow high standard
images. The spatial data was download from Geo-Eye
(Google Earth) using the UMD application.GeoEye-
1/Digital Globe (Google Earth) has a resolution of 0.41-
meter on panchromatic and 1.65-meter on multispectral
imagery (Setiabudi et al. 2013). To cover Bekol savanna
and the surrounding, many such small GeoEye-1 images
were constructed by the UMD and stored in JPEG files to
be merged and integrated into one mosaic of GeoEye-1
image. Finally the mosaic image was rectified or geo-
referenced using coordinate data from Google Earth. The
data were projected into WGS 1984-UTM, Zone_49S. In
this way a detailed vegetative map was developed. The
identification of A. nilotica stand is based on prior
knowledge of the plant from the preliminary field
observation in 2013. The interpretation result and up-date
data was also checked through ground-truth observation in
the field in 2014. Ground/field observation in 2014 was
then compared with 2013 satellite image and was displayed
using ARC-MAP software from ARC GIS.
RESULTS AND DISCUSSION
Our observation result analysis showed that in terms of
the three most important tree species (described in
Importance Value Index/IVI) in all of the sites that we
sampled (grazed, burnt and unburnt savannas) A. nilotica
appeared in each of these sites (Figure 3). The values
however, vary between sites. A. nilotica IVI is highest in
the unburnt savanna, with IVI reaching almost 250. The
unburnt site is actually a burnt site but with moderate age
or time since fire (approximately 6-7 years), whereas the
burnt site is savanna with relatively young age/time since
fire (few months to 1 year). It is assumed that A. nilotica
pods grazed by buffalo and spread the seeds to many areas
of savanna including the burnt areas. Once it was
experienced fire, the heat assisted in scarification process
of the seeds and speed up the germination. When there was
no subsequent fire for significant period of time, these
seeds grow and become mature and dominating the unburnt
site. In terms of species diversity, all of these sites have
low species diversity (around 0.8) as measured by Shannon
and Wiener and Simpson Index (Table 1). This is perhaps,
due to over dominance of certain species, as can be seen
from the next graph.
Ordination analysis (Figure 4) shows that the grazed
and ungrazed sites were not as different in terms of the
species composition as shown by the close position
between the dots that represent the two sites and sometimes
these dots were mixed. Whereas when we look at the burn
site, we notice that the dot that represent the burn site is
clearly separated from the other two sites although the
points of the burn area were also has different pattern,
some are clumped and some are scattered. These results
imply that it is difficult to find a site that is purely ungrazed
as animals move around in such a dynamic pace. We can
only assume that site/plots that have no traces of
scats/stools or remains of the herbivore to be the ungrazed
site, however we know now that it is not adequate.
Therefore the ungrazed and grazed sites have did not
separate very well and imply that these sites has similarity
Table 1. Species diversity in three sampling sites
Index Shannon
Index Simpson
Un-grazed
0.83080091
0.437944506
Grazed
0.845667704
0.447737829
Burnt
0.745068622
0.45753436
Figure 3. Importance Value Index analysis for tree habits at the sampling sites in Bekol Savanna, Baluran National Park, East Java,
Indonesia
SUTOMO et al. – Acacia nilotica stand expansion in Baluran National Park, Indonesia
99
Figure 5. Result from GIS analysis and ground check showing expansion of Acacia nilotica stand at Bekol Savanna in 2014, Baluran
National Park, East Java, Indonesia
Figure 6. A profile diagram of the boundary area between the A. nilotica stand and Bekol Savanna, Baluran National Park, East Java,
Indonesia. Notes: An = Acacia nilotica, Ai = Azadirachta indica, Zr = Ziziphus rotundifolia, Pa = Polytrias amaura, Dc = Dichantium
coricosum, Tl = Thespesia lampas
