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American Journal of Environmental Sciences 6 (4): 389-394, 2010
ISSN 1553-345X
© 2010 Science Publications
Corresponding Author: Arifin Abdu, Department of Forest Management, Faculty of Forestry, University Putra Malaysia,
43400 UPM Serdang, Selangor, Malaysia Tel: +60389467177 Fax:+60389432514
389
Selected Soil Morphological, Mineralogical and Sesquioxide
Properties of Rehabilitated and Secondary Forests
1
B.T. Saga,
1
O.H. Ahmed,
2
A.S. Jamaluddin
2,3
H. Abdul-Hamid,
4
S. Jusop,
2
N.M. Nik Ab. Majid,
5
A. Hassan,
2
K.H. Yusof and
2,3
Arifin Abdu
1
Department of Crop Science, Faculty of Agriculture and Food Sciences,
University Putra Malaysia Bintulu Sarawak Campus, 97008 Bintulu, Sarawak
2
Department of Forest Management, Faculty of Forestry,
3
Laboratory of Sustainable Bioresource Management,
Institute of Tropical Forestry and Forest Products,
4
Department of Land Management, Faculty of Agriculture,
University Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
5
School of International Tropical Forestry, University Malaysia Sabah, 88999 Sabah, Malaysia
Abstract: Problem statement: The tropical rain forests in Southeast Asia have been characterized by
several researchers. However empirical data on soil characteristics under degraded forest land in
tropical rain forest and rehabilitated program are limited. A study was conducted to evaluate the soil
morphology, mineralogical and sesquioxide properties of a rehabilitated degraded forest land (19 years
after it was planted with various indigenous species) in comparison with an adjacent secondary forest.
Approach: Soil samples were air-dried and pass through a 2 mm sieve. Soil morphology was
determined based on field observation. The non-crystalline (amorphous) of Al, Fe and Si oxides and
hydroxides (Alo, Feo and Sio) were extracted with ammonium oxalate while the Dithionate-Citrate-
Bicarbonate (DCB) method was used for extracting (crystalline) the Al, Fe and Si oxides and
hydroxides (Ald, Fed and Sid). The concentrations of extracted Al, Fe and Si were determined by
atomic absorption spectroscopy. Mineralogical compositions were identified by X-ray diffraction
method. Results: The A-horizon of secondary forest was darker and thicker than that of the
rehabilitated forest. Root mat at the secondary forest was well-developed compared to the rehabilitated
forest. The clay minerals were dominated with kaolinite and illite to a lesser extent of goethite and
hematite accompanied with low values of activity ratio of Al and Fe oxides and hydroxides, indicating
that the soils were highly weathered. Conclusion/Recommendations: The difference between
rehabilitated and secondary forests was root abundance where secondary forest had most. Good root
penetration in the secondary forest indicates that the soil texture there was not heavy. Soils in the
rehabilitated and secondary forests were strongly weathered (high presence of kaolin minerals), but the
low presence of sesquioxides suggests that they are yet to reached the ultimately weathered phase. The
soil properties in terms of morphology, sesquioxides and clay minerals should be taken into account
for better management of forest rehabilitation program in tropical regions.
Key words: Soil morphology, mineralogical, sesquioxide, rehabilitated and secondary forests
INTRODUCTION
Malaysia is made up of 19.01 million ha or 57.9%
of the total land area, with Sabah and Sarawak having
the larger proportion of forest than Peninsular Malaysia.
Malaysia has a total area of 16 million ha of natural
forest, of which 14.19 million ha are designated as
Permanent Forest Estate (PFE) or forest reserve.
Approximately 10.53 million ha of the PFE are
production forests with the remaining 3.66 million ha
being protection forests. About 1.8 million ha located
outside the PFE are designated as national parks and
wildlife sanctuaries (Shahwahid, 2004). From 1963-
1985, 30% of the forests in Sarawak had been lost due
to deforestation and logging activities (Leng et al.,
2009).
Am. J. Environ. Sci., 6 (4): 389-394, 2010
390
Agricultural conversions, shifting cultivation and
timber harvesting in Malaysia is the main cause of
degradation. Conversion of large scale of forested areas
into oil palm and rubber plantations significantly causes
land degradation in Peninsular Malaysia and shifting
cultivation is the main cause of degradation in Sarawak.
Iban and Bidayuh are the common natives who are
involved in shifting cultivation along rivers in Sarawak.
The increase of cultivation area is due to the increase of
population growth. The figures based on satellite
imaginaries of 1990-1991 showed that the total area
affected by shifting cultivation was 3 million ha in
Sarawak (Jomo et al., 2004).
Forest degradation may adversely affect our nature
and ecosystem. The most common effect of degradation
is climate change. Trees act as the major storage depot
for the carbon; they absorb the carbon dioxide from
atmosphere and produce fats, carbohydrate and protein
of trees. When forest degradation occurs, trees are
burnt, this causes the carbon dioxide to be released to
the atmosphere and the concentration of carbon dioxide
in the atmosphere increases. Soils are also affected as a
result of forest degradation processes. The main effect
of soil due to the degradation is soil erosion. As forests
are cleared, soils are directly exposed to the sun and as
a result, they get dried and become infertile. Moreover,
soil nutrient stock could be lost as a result of poor soil
texture and structure. This also destroys biodiversity of
species and habitat. Therefore, if the economic,
environmental, social and cultural benefits of the forest
are to be continuously enjoyed, the damage has to be
repaired by various technical approaches, such as
rehabilitation, afforestation and reforestation.
Rehabilitation program is the process of making
land useful again after disturbance. It involves the
recovery of ecosystem function and processes in the
degraded habitat. In afforestation program, the
management strategies applied to degraded forestland
aims to restore the capacity of a forest in order to
produce a high quality product while reforestation
program is necessary both to rehabilitate the
deteriorating ecosystem and sustain the forest resource
(Montagnini and Jordan, 2005). Several rehabilitation
efforts using different technique have been carried out
in Malaysia with varying degrees of success. One
technique that has been successful in the warm
temperate zone is dense planting (Miyawaki, 1993).
This technique was used in Bintulu, Sarawak to
rehabilitate the degraded shifting cultivation areas with
indigenous tree species. The indigenous tree species
recommended at checkboard are: Shorea ovata, S.
mecistopteryx, S. macrophylla, Dryobalanops
aromatica, Parashorea parvifolia, Hopea beccariana,
Durio carinatus and Eusideroxylon zwagery (Alias et al.,
1998). The soil morphological, mineralogical and
sesquioxides of the rehabilitated forest are yet to be
studied. Therefore, a study was conducted to evaluate
the soil morphology, mineralogical and sesquioxide of a
rehabilitated degraded forest land (19 years after it was
planted with various indigenous species) with special
reference to the soils in adjacent secondary forests.
MATERIALS AND METHODS
This research was carried at University Putra
Malaysia Bintulu Campus Sarawak. The study site was
about 600 km northeast of Kuching the capital city of
Sarawak, latitude 03°12’N, longitude 113°02’E at 50 m
above sea level. The mean annual rainfall is about 2993
mm and the mean daily temperature is 27°C. The mean
monthly relative humidity of the area is usually above
80% and slightly lower during rainy season.
Sampling plots of 20×20 m were established for
each group or stand ages of the rehabilitated forest. Soil
profile (0-20, 20-40, 40-60, 60-80 and 80-100 cm
depth) in each particular site was dug for soil
characterization. The soil morphology was determined
based on field observation. The morphological
variables determined were field soil texture, soil color,
horizon and boundary, root abundance and soil
consistency.
In the case of oxides and hydroxides (Al, Fe and
Si) and clay mineral compositions (kaolinite, illite,
hematite and goethite), soil samples were taken from
topsoil (0-20 cm). Five sub-samples were taken from
each corner and the middle of the plot and they were
homogenized to make a composite sample. This was
applicable to all plots. Proper labeling was done to
avoid identification error during transfer. These
composite samples were air-dried, homogenized and
sieved to pass a 2 mm sieve for further analysis.
The Dithionate-Citrate-Bicarbonate (DCB) method
as described by Mehra and Jackson (1960) was used for
the determination of Al, Fe and Si oxides and
hydroxides (Ald, Fed and Sid). The non-crystalline
(amorphous) of Al, Fe and Si oxides and hydroxides
(Alo, Feo and Sio) were determined by using
inductively coupled plasma atomic emission
spectrophotometry (ICP-MS) after extracting the soil
with 0.2 mol L
−1
ammonium oxalate at pH 3.0 by
reciprocal shaking in the dark for 1 h (MacKeague and
Day, 1966).
The XRD analyses were carried out using clay
fraction isolated from soils that pretreated with H
2
O
2
for Organic Matter (OM) removal. About 10 g of 2 mm
air-dried soil was weighted into 1000 mL beaker and
Am. J. Environ. Sci., 6 (4): 389-394, 2010
391
treated with 30% H
2
O
2
until all OM was destroyed,
followed by heating to about 90°C to remove the excess
H
2
O
2
. The sample was then washing with distilled
water before transferring into a 250 mL centrifuge tube.
The iron oxides were removed by adding 150 mL of
citrate-bicarbonate buffer (0.3 M sodium citrate and
added with 125 mL of 1 M sodium bicarbonate) and 3 g
sodium Dithionite (CBD) before putting into a water
bath at 80°C and intermittently stirred for 20 min. This
treatment was performed twice prior to addition of
10 mL of solution containing 0.35 M sodium
hexametaphosphate and 0.07 M Na
2
CO
3
and dispersed
using a mixer. The clay fraction was separated by
gravimetric sedimentation. It was expected that only
phyllosilicates would be detected by XRD from this
treatment, since iron oxides have been removed. The
treated clay specimen then prepared on the glass slide
and run on Philip PW 3040/60 X’pert Pro X-ray
diffractometer, using CuK-alpha radiation target,
operated at 40 kV and 30 mA. The oriented specimens
were scanned from 3-50° 2θ at 1° min
−1
. XRD data
were collected and stored with connected PC. Semi-
quantative estimation of the mineral proportion was
calculated from the height of a first peak order times the
width at half height.
The ANOVA (analysis of variance) followed by a
Tukey’s HSD test were used to test any significant
difference of the means of sesquioxides and clay
minerals properties between plots of rehabilitated and
secondary forests. Statistical Analysis System version
9.1 was used for the statistical analysis.
RESULTS
Table 1 shows the main features of the soil
morphological properties at the study sites. The soil at
the study site was deep (more than about 100 cm) with
clayey texture. The difference was color and thickness
of A-horizon. The Nirwana pedon in the lowland areas
of the secondary forest, the surface area was only 0-13
cm in thickness and it was darker than other sites. The
darker color of A-horizon was due to higher contents of
soil organic matter. The minimum thickness of the
other A-horizons were 15 cm with a range 0-20 cm.
Root mat at Nirwana was well-developed compared to
the others sites. On the others sites, grass root was
found in the surface horizon.
The sesquioxide properties of the soil at the
different plots are shown in Table 2. Generally, the
level of Alo, Feo, Ald and Fed were very low,
indicating no translocation of amorphous and
crystalline oxides. There was no major difference
between the contents of Al and Fe at all this plot. For
Alo, there was no significant difference between plots.
Table 1: Morphological properties of rehabilitated and secondary forests
Plot Depth (cm) Horizon Color Texture Root Consistency
Phase 1 0-17 A 10TR4/4 SCL FeC Fri
1991 17-60 bt1 10YR7/8 SCL FeC Fri
60-106 Bt2 10YR6/8 SCL FeF Fri
106-150 Bt3 10YR6/8 SCL nf Fri
Phase 2 0-20 A 7.5YR5/6 L FeC Fri
1995 20-40 B 7.5YR5/8 L FeF Fri
40-90 BC1 10YR4/3 L nf Fri
90-150 BC2 10YR6/8 L nf Fri
Phase 3 0-15 A 7.5YR7/6 SC FeC Vfri
2002 15-42 Bt1 10YR6/8 SC FeF Fri
24-69 Bt2 7.5YR7/6 SC nf Fri
69-100 C 5YR6/1 SC nf Fri
>100 R 5R2/3 NT nf nd
Phase 4 0-16 A1 10YR4/4 SC FeC Fri
2008 16-98 Bt1 10YR6/8 SC FeF Fri
46-98 Bt2 10YR6/8 SC nf Fri
98-120 Bt3 10YR5/8 SC nf Fri
120-150 C 5YR6/3 SC nf Fri
Nirwana 1 0-20 A 7.5YR3/2 SCL FeC Fri
20-46 Bt1 10YR6/6 SC MeC Fi
46-94 Bt2 10YR6/8 SC FeF Fi
94-110 Bt3 10YR7/8 SC FeF Fi
Nirwana 2 0-13 A1 10YR3/2 SC MaC Fri
13-26 Bt1 10YR6/6 SC FeF Fri
26-66 Bt2 10YR7/8 SC FeC Fri
66-100 Bt3 10YR6/8 SC FeF Fri
Note: Texture: SCL: Sandy clay loam; SC: Sandy clay; L: Loam; NT: No texture Abundance: Fe: Few, Ma: Many, nf: not found, Size: C:
Coarse, F: Fine, Me: Medium; Consistency: Fi: Firm, Fri: Friable, Vfri: Very friable
Am. J. Environ. Sci., 6 (4): 389-394, 2010
392
Table 2: Sesquioxide contents of rehabilitated and secondary forests
Oxalate extractant
a
(g kg
−1
)
DCB extractant
b
(g kg
−1
)
---------------------------------------------- --------------------------------------------------------------------------------
Plot Alo Feo Sio Ald Fed Sid Alo/Ald Feo/Fed
1991 0.26
a
0.22
bc
<0.0001
ab
0.59
ab
3.61
a
0.38 0.44
ab
0.06
c
1993 0.20
a
0.20
c
<0.0001
ab
0.33
ab
1.70
b
nd 0.61
sb
0.12
ab
1995 0.19
a
0.28
abc
<0.0001
ab
0.42
ab
2.26
b
nd 0.45
ab
0.12
ab
1996 0.20
a
0.23
abc
<0.0001
ab
0.63
c
1.58
b
nd 0.32
c
0.15
ab
1997 0.21
a
0.29
abc
<0.0001
ab
0.37
ab
1.98
b
nd 0.57
b
0.15
ab
1998 0.24
a
0.34
abc
<0.0001
ab
0.32
ab
1.72
b
nd 0.75
a
0.20
a
1999 0.24
a
0.27
abc
0.05
ab
0.5
b
1.79
b
nd 0.48
bc
0.15
ab
2000 0.27
a
0.33
abc
<0.0001
ab
0.4
ab
1.66
b
nd 0.68
c
0.20
a
2001 0.17
a
0.25
abc
<0.0001
ab
0.42
ab
1.61
b
nd 0.40
bc
0.16
ab
2002 0.14
a
0.04
abc
0.04
ab
0.45
ab
1.55
b
nd 0.31
bc
0.03
c
2003 0.13
a
0.36
abc
0.04
ab
0.3
ab
1.92
b
nd 0.43
bc
0.19
a
2004 0.22
a
0.23
abc
<0.0001
ab
0.5
ab
1.54
b
nd 0.44
bc
0.15
a
2005 0.14
a
0.42
a
0.04
ab
0.31
ab
1.92
b
nd 0.45
bc
0.22
a
2006 0.11
a
0.30
abc
0.03
ab
0.23
ab
1.67
c
nd 0.48 0.18
a
2007 0.16
a
0.23
abc
<0.0001
ab
0.32
ab
1.38
b
nd 0.51
b
0.17
a
2008 0.27
a
0.20
c
<0.0001
ab
0.32
ab
1.57
b
nd 0.84
a
0.13
a
Nirwana 1 0.11
a
0.30
abc
0.05
ab
0.31
ab
1.46
b
nd 0.35
c
0.21
a
Nirwana 2 0.14
a
0.32
abc
0.5
a
0.42
ab
2.12
b
nd 0.33
c
0.15
ab
Note: Means with different letters within column indicate significant difference at P <0.05 between plots by Tukey’s (HSD) test;
a
: Amounts of
Al and Fe extracted by ammonium oxalate.
b
: Amounts of Al and Fe extracted by a dithionate citrate system buffered with sodium bicarbonate.
nd: Not determined
Table 3: Clay mineral compositions of rehabilitated and secondary
forests
Plot it Kt Gt Ht
1991 ++++
a
++++
a
+ ±
1993 +++
a
++++
a
+ nd
1995 +++
a
+++
ab
±
1996 +++
a
++
b
nd nd
1997 +++
a
++++
a
+ nd
1998 ++
ab
+++
ab
nd nd
1999 ++
ab
++++
a
± nd
2000 +++
a
++++
a
+ nd
2001 ++
ab
++++
a
nd nd
2002 ++
ab
++++
a
nd nd
2003 ++
ab
++
b
nd nd
2004 +
b
++++
a
nd nd
2005 +++
a
++++
a
nd nd
2006 ++
ba
++++
a
nd nd
2007 +++
a
++++
a
+ nd
2008 +++
a
++++
a
+ ±
Nirwana 1 ++++
a
++
b
± nd
Nirwana 2 +
b
++++
a
± nd
Note: Means with different letters within column indicate significant
difference at p≤0.05 between plots by Tukey’s (HSD) test. It: Illite,
Kt: Kaolinite, Gt: Goethite, Ht: Hematite, nd: not determined, ±:0-
5%, +:5-20%, ++:20-40%, +++:40-60%, ++++ : >60%
The maximum mean was 0.26 at plot 2000 and the
minimum mean for the Alo was 0.105 at Nirwana 1.
For Feo, the highest value was recorded at plot 2005
which significantly different with plots 1991, 2004 and
2008, whereas there was no significant difference found
with the other plots. The lowest mean for Feo was
recorded at plot 2008 with 0.19. For Sio, there was
significant difference between plots and some of the Sio
were absent in some plots. The highest mean of Sio
content was 0.05 it was found at Nirwana 2. For Ald,
there was significant difference among the plots. The
highest mean was 0.62 it was found at plot 1996.
Meanwhile the lowest mean of Ald was 0.22 at plot
2006. Meanwhile for Feo, there was significant
difference between the plots. The highest mean was
3.61 at 1991. Meanwhile the lowest mean was 1.37 at
plot 2007. The content of Sid was almost not found of
the soils studied except in plot 1991. The activity ratios
of Al and Fe oxides and hydroxides were regarded low.
The clay minerals composition of the soils both at
rehabilitated and secondary forests are shown in Table 3.
The results showed that the clay minerals were
dominated by kaolin minerals followed by illite to a
lesser extent of goethite and hematite. The abundant
amount of kaolinite and small value of goethite and
hematite revealed that the soils in the present study
were highly weathered.
DISCUSSION
Wambeke (1992) stated that, the greater the rain
intensity, the greater the proportion of large drops and
the faster their terminal fall velocities will affect the
erosivity. The tropical rains have higher drops. For
these reasons, frequent heavy rainfall might have
caused a severe erosion of the surface soil and
therefore subsurface soils became a current surface
layer. Alias et al. (1998) stated that the soil of the study
site belongs to Bekenu and Nyalau Series. According to
Soil Survey Staff (1999) Bekenu Series are fine loamy
red yellow podzolic group with hue color of 10YR
within 50 cm. The Nyalau Series is characterized by the
Am. J. Environ. Sci., 6 (4): 389-394, 2010
393
coarse loamy red yellow podzolic group that developed
from sandstone. The Bekenu and Nyalau Series have a
brownish yellow A-horizon over a yellow B horizon.
The darker color of the A-horizon at Nirwana (down)
compared to other pedons suggests sufficient duration
to accumulate soil organic matter. Root elongation was
shallower in most of the sites except for the secondary
forest. This result suggests that most of the sites had
high clay content with lower levels of nutrients and
more acidic nature. Sakurai et al. (1995) stated that root
elongations as well as tree growth are restricted by the
combination of a heavy texture with strong acidity.
In the case of sesquioxide, the contents of Alo,
Feo, Ald and Fed were very low in all of the plots.
Sakurai et al. (1996) studied this type of soil from four
different regions in Thailand and they stated that soils
with high activity ratios of Al and Fe indicate strong
weathering. Zaidey et al. (2010) stated that a lack of
major difference between Al and Fe might be related to
desilication in the soil upon weathering and leaching. It
suggests that the low amount of Al and Fe were related
to the weathering and through leaching in both forests.
The values of Alo in all the plots were similar. This
suggests that the amount of organic matter were similar.
This also indicates no translocation of amorphous and
crystalline oxide (Abdu et al., 2007). The highest
content of Feo indicates that this plot received a
significant amount of organic matter. This organic
matter can stabilize the free Fe as in the form of oxides
(Ishizuka et al., 2000). The reductive condition in the
soil also can cause the Fe oxide to easily dissolve. This
dissolved Fe could be oxidized and accumulated in the
surface horizon. The factor of leaching of amorphous
fraction of this element may be smaller compared to
other plots.
The ratio of Al and Fe oxides and hydroxides of
the soils usually refer to a relative indicator of the
degree of crystallinity of free Fe oxides (Sakurai et al.,
1996). He further illustrates that the activity ratio of Al
and Fe oxides and hydroxides of the soils less than 0.10
were reached to the ultimately weathered. The Fe and
Al oxides and hydroxides become more crystallized
upon weathering process going on due to the loss of
active hydroxyl groups which eventually lead to a value
below 0.10. In general, the activity ratios of Al and Fe
oxides and hydroxides in this study were higher than
reported by Sakurai et al., (1996) implies that the soils
were highly weathered but are not reach the ultimately
weathered stage.
Table 3 shows that kaolinite was the dominant clay
minerals followed by illite, whereas goethite and
hematite were not dominant. The dominance of
kaolinite could be ascribed to the granitic parent
materials (Zaidey et al., 2010). The present of kaolin
minerals in the rehabilitated and secondary forests
indicated that the soils were strongly weathered, typical
of Ultisols (Ohta and Syarif, 1992; Ohta et al., 1993;
Hattori et al., 2005). According to Eswaran et al.
(1990) kaolinite and gibbsite are produced faster in the
humid tropical region without any distinct dry season.
This also suggests that the amount of rainfall and dry
season in this region have significant impact on kaolin
formation. The presence of illite indicates that
successive supply of new materials for soil formation
affected weathering in all plots. It also indicates that
the presence of illite in soil takes a long time weathered
to kaolinite (Watanabe et al., 2006). The presence of
hematite is characterized by intense weathering. The
presence of small amount of goethite and hematite also
suggests that they were removed selectively in event of
weathering processes and soil erosion.
CONCLUSION
The difference between rehabilitated and secondary
forests was root abundance where secondary forest had
most. Good root penetration in the secondary forest
indicates that the soil texture there was not too heavy.
Soils in the rehabilitated and secondary forests were
strongly weathered (high presence of kaolin minerals),
but the low presence of sesquioxides suggest that they
are yet to reach the ultimately weathered phase. The
soil variable in terms of morphology, sesquioxides and
clay minerals compositions should be taken into
consideration for appropriate management of
rehabilitation or afforestation programs in tropical
regions in particular tropical soils of Malaysia which
regarded highly weathered and concomitantly low in
fertility.
ACKNOWLEDGEMENT
This research was financially supported by the
Ministry of Higher Education of Malaysia (MOHE)
under Research University Grant Scheme (RUGS-03-
01-09-0704) through University Putra Malaysia,
Malaysia (UPM). We wish to express our gratitude to
the staff of the Department of Crop Production,
University Putra Malaysia, Bintulu Sarawak Campus,
Faculty of Forestry and Faculty of Agriculture,
University Putra Malaysia during field sampling and
laboratory analysis. We would like to thank to the of
the final year students (Bachelor Scince of
Bioindustry), University Putra Malaysia, Bintulu
Sarawak Campus for their contribution in helping
digging the soil profiles and measuring the growth of
planted trees as well as vegetation survey.
Am. J. Environ. Sci., 6 (4): 389-394, 2010
394
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