Chemosphere 52 (2003) 603–608
www.elsevier.com/locate/chemosphere
Seasonal changes of CO2, CH4 and N2O fluxes in relation
to land-use change in tropical peatlands located in coastal
area of South Kalimantan
K. Inubushi
a,*
, Y. Furukawa a, A. Hadi b, E. Purnomo b, H. Tsuruta
c
a
Faculty of Horticulture, Chiba University, Matsudo, Chiba 271-8510, Japan
Faculty of Agriculture, Lambung Mangkurat University, Banjarbaru 70714, Indonesia
National Institute for Agro-Environmental Sciences, Kan-nodai, Tsukuba 305-8604, Japan
b
c
Abstract
Tropical peatland could be a source of greenhouse gases emission because it contains large amounts of soil carbon
and nitrogen. However these emissions are strongly influenced by soil moisture conditions. Tropical climate is characterized typically by wet and dry seasons. Seasonal changes in the emission of carbon dioxide (CO2 ), methane (CH4 )
and nitrous oxide (N2 O) were investigated over a year at three sites (secondary forest, paddy field and upland field) in
the tropical peatland in South Kalimantan, Indonesia. The amount of these gases emitted from the fields varied widely
according to the seasonal pattern of precipitation, especially methane emission rates were positively correlated with
precipitation. Converting from secondary forest peatland to paddy field tended to increase annual emissions of CO2 and
CH4 to the atmosphere (from 1.2 to 1.5 kg CO2 -C m2 y1 and from 1.2 to 1.9 g CH4 -C m2 y1 ), while changing landuse from secondary forest to upland tended to decrease these gases emissions (from 1.2 to 1.0 kg CO2 -C m2 y1 and
from 1.2 to 0.6 g CH4 -C m2 y1 ), but no clear trend was observed for N2 O which kept negative value as annual rates at
three sites.
Ó 2003 Elsevier Science Ltd. All rights reserved.
Keywords: Carbon dioxide; Histosol; Land-cover change; Methane; Nitrous oxide; Peat
1. Introduction
Peatlands are technically defined as all lands where
80% of the area is covered by peat soil; a soil containing
at least 30% by weight of organic matter, in cumulative
layer of 40 cm or more (FAO, 1988), and typical landcover in wetland. Although wetlands occupy only 4–6%
of the landÕs surface in the world (about 530–570 million
ha) (Aselmann and Crutzen, 1989), it contains about 20–
25% of terrestrial carbon and nitrogen (Batjes, 1996).
About 29 million ha is in the tropical zone, and a large
*
Corresponding author. Fax: +81-47-308-8720.
E-mail address: [email protected] (K. Inubushi).
portion of this tropical peat soil exists in the Borneo
Island (Driesen, 1978; Takai, 1997).
Tropical peatland could be a source of greenhouse
gases emission because it contains large amounts of soil
carbon (70 Gt; Immirzi et al., 1992) and nitrogen (Ismunadji and Soepardi, 1984; Driesen, 1978). The organic
matter in the peat soils is naturally decomposed slowly
but continuously. Decomposition of organic matter is
basically the degradation of complex organic compounds, converting them partly to the simpler forms.
The decomposition causes the loss of mass (commonly
stated as ground subsidence) and releases by-products
leading to the formation of a more stable peat soil.
The demands of peatland for agricultural and aquacultural uses have been increasing (Ahmad et al., 1986;
Radjagukguk, 1990; Kyuma, 1992). The conversion of
0045-6535/03/$ - see front matter Ó 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0045-6535(03)00242-X
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K. Inubushi et al. / Chemosphere 52 (2003) 603–608
peatland always starts with the construction of drainage
ditches in order to reduce the excess water that is commonly associated with natural peatland. Both natural
and converted tropical peat soil can potentially control
the dynamics of carbon dioxide (CO2 ), methane (CH4 )
and nitrous oxide (N2 O) (Bouwman, 1990). However,
there is no quantitative data on the emission of these
three gases from tropical peat soils, except our preliminary reports (Hadi et al., 2000) for the three gases from
same area, Hadi et al. (2001) for N2 O from same state
but inland peat soil, and Kiese and Butterbach-Bahl
(2002) for N2 O and CO2 from tropical wet forest but not
in peat soil. Moreover, seasonal changes of these gas
emissions in tropical peat soil are poorly understood.
Since the tropical climate is characterized typically by
wet and dry seasons, seasonal patterns of these emissions are important for better estimations of the emissions, which are strongly influenced by soil moisture
conditions. The present study was undertaken to investigate seasonal changes in the emission of CO2 , CH4 and
N2 O over a year in relation to land-use change of
tropical peatland in South Kalimantan, Indonesia.
2. Materials and methods
2.1. Site description
The monthly measurements took place at the peatland near Gambut in South Kalimantan, Indonesia
(Table 1). Traditional peatland reclamation in these area
started in 1935, but intensive reclamation with construction of canals has been going on to establish paddy
and then upland fields since late 1970s. Vegetation before the intensive reclamation was covered mostly by
Macaranga sp. tree (up to 20 m) with Acrostichum
aureum ferns (1–2.3 m height) (Sabiham, 1988, 1989),
which still remain partly as secondary forest. Three sites
were chosen to represent different land-uses; G-3––secondary forest, G-2––paddy field, and G-1––upland field,
although paddy or upland crops have no longer produced due to their low fertilities, so they were nearly
abandoned fields. However general land use change in
this area is from secondary forest to paddy, then upland/
paddy rotation in 2–5 years intervals. Each site was
surveyed following 100 100 m separate grids, so totally
Table 1
Site location, description and physicochemical properties of the soils used (November 1999)
Site
code
Location and
land-use
management
Peat
thickness
(cm)
Ground
watera
(cm)
Sample
depth
(cm)
H2 O
KCl
G-1
Abandoned upland crops field
00
(3°250 43 S, 114°
00
0
40 26 E)
70–100
)15.1
0–10
10–20
20–30
3.8
3.4
3.2
G-2
Abandoned
paddy field
00
(3°250 51 S, 114°
00
0
40 14 E)
10–40
+2.1
0–10
10–20
20–30
G-3
Secondary forest
00
(3°250 53 S,
00
0
114°41 11 E)
100–200
)10.0
Ash
(%)
Total
organic C
(g kg1 )
Total N
(g kg1 )
G-1
35.6
48.6
46.4
486
306
338
9.6
4.8
5.9
778
474
578
G-2
8.2
2.4
3.3
613
620
616
15.0
12.8
8.9
G-3
7.8
3.9
2.9
486
368
506
15.9
10.1
9.7
a
Eh (mV)
EC
(mS m1 )
CEC
(cmol (+)
kg1 )
3.0
2.9
2.0
358
7
157
14.1
17.6
20.1
75.8
92.0
103.2
3.8
3.6
3.8
3.0
3.0
3.1
124
)10
)81
23.3
14.4
12.5
132.8
70.6
72.7
0–10
10–20
20–30
3.2
3.0
3.3
2.3
2.3
2.3
323
60
185
27.7
19.7
14.7
103.4
71.0
108.1
Soluble
organic C
(mg kg1 )
NHþ
4
(mg kg1 )
NO
3
(mg kg1 )
Fe2þ
(mg kg1 )
397
220
121
46.6
10.5
11.9
<12
<12
<12
1432
1456
507
788
1150
634
31.3
20.7
18.8
31.1
19.6
28.7
1167
1444
1093
571
637
1362
24.9
24.0
29.0
12.1
<12
<12
pH
Negative values for ground water table mean that it was below the ground surface.
K. Inubushi et al. / Chemosphere 52 (2003) 603–608
three grids were set up. Distance between G-1 and G-2
was about 450 m and these sites were about 1.4–1.7 km
away from G-3. In all sites, the peat soils were derived
from a mixture of wood and grass (Sabiham, 1988, 1989;
Inubushi et al., 1998). The depth of the peat layers
varied from 10 cm to about 2 m.
2.2. Chemical properties of soil samples
Soil samples were taken in November 1999 from 3
depths (0–10, 10–20, 20–30 cm) and used for laboratory
measurement. The samples were kept in cold room (4 °C)
until the time of use. Soil pH was measured with glass
electrode after 1 h shaking with distilled water or KCl
solution using a 1:5 (soil:water or KCl) ratio. Soil EC
(electrical conductivity), CEC, ash, total C and N contents were determined according to the standard method
of soil analysis (Black et al., 1981). The concentrations
of ammonium and nitrate-N were measured in 2 M KCl
extract by using the nitroprusside (Anderson and Ingram, 1989) and hydrazine reduction (Hayashi et al.,
1997) methods, while Fe2þ by Merck RQ Frex plus
(Sigma, Germany) after acetate extraction (pH 2.8), respectively. The amount of soluble organic C was measured by TOC meter (Shimadzu, TOC 5000) after 1 h
extraction with distilled water at 1:5 ratios.
2.3. Greenhouse gases emission from tropical peatland
Seasonal field measurements were conducted at three
sites (G-1, G-2 and G-3) from November 1999 to January 2001 almost monthly in order to find temporal
pattern of the emission of greenhouse gases from tropical peatlands. Rates of CO2 , CH4 and N2 O emissions
were measured by the closed cylindrical chamber method
(inner dia. 21.0 cm; height 14.0 cm). Gas samples were
605
taken with gas-tight syringe from the triplicate chamber
and the concentrations of CO2 , CH4 and N2 O were
quantified with gas chromatograph (Shimadzu 7A,
Japan) equipped with thermal detector, frame ionized
detector, and electron capture detector, respectively.
Redox potential (Eh ) was measured with platinum electrodes at 10, 20 and 30 cm depth in the field. Ground
water table was measured by a pizometer inserted into
the soil.
3. Results and discussion
3.1. Chemical properties of soil samples
Soil samples showed low pH in both water and KCl
extract and contained 30–62% carbon and 0.5–1.6% nitrogen (Table 1). These characteristics are typical in the
peat soils (Driesen, 1978; Ismunadji and Soepardi, 1984;
Batjes, 1996; Bozkurt et al., 2001). High total C contents
especially in G-2 were possibly derived partly from
charcoal after natural fire in the past and deep plowing
during land preparation for rice cultivation. During
these land-use changes, water soluble C was also accumulated, while total nitrogen contents were relatively
low. Water table was high in abandoned paddy field
(G-2), so that soil Eh was relatively low and NHþ
4 and
Fe2þ contents more in G-2 compared to others.
3.2. Seasonal changes of CO2 , CH4 and N2 O emission
from tropical peatlands
These gases emitted from the fields varied widely over
a year (Fig. 1). CO2 was in the range from 40 to 380 mg
C m2 h1 and rather high in March–May and December. CH4 was in the range from 0 to 1 mg C m2 h1 and
Fig. 1. Seasonal changes in CO2 , CH4 and N2 O flux from tropical peatland in South Kalimantan as influenced by land-use management.
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K. Inubushi et al. / Chemosphere 52 (2003) 603–608
higher in February–April than the rest of year. These
gases did not show significant negative flux. While N2 O
was in the range from )0.04 to +0.03 mg N m2 h1 ,
significant negative flux for 8 flux measurements during
February–June and January among 33 measurements
were indicating N2 O consumption from the atmosphere
by soil microorganisms.
In order to examine controlling factor of these gases
emission, monthly means of precipitations and air temperatures were calculated as averages between those in
Balikpapan (01°160 S, 116°540 E, 3m asl) and Pontianak
(00°090 S, 109°240 E, 3m asl) where are the nearest
available locations (NOAA, 2001). Although monthly
mean air temperature was almost constant at 26–27 °C
precipitation showed clear seasonal pattern (Fig. 2).
Highest precipitation was observed around March when
CH4 emission at three locations reached their peaks. The
CO2 emission had no tendency to the changes in precipitation.
Seasonal pattern of N2 O was not clear due to high
variability particularly in large among the locations as
similar to CO2 pattern. According to the correlation
between precipitation and gas emission, CH4 emission
was positively correlated with precipitation (Fig. 3),
while N2 O was slightly but significantly correlated negatively with precipitation when G-1 data were excluded
(Fig. 4).
Emission of greenhouse gases is likely influenced by
precipitation directly and indirectly. Soil moisture is one
of the most important controlling factors for biological
reactions in soil, including heterotrophic microorgan-
Fig. 3. Correlation between precipitation and methane flux in
three sites in South Kalimantan (p < 0:01).
Fig. 4. Correlation between precipitation and N2 O flux in sites
G-2 and G-3 in South Kalimantan (p < 0:05).
Fig. 2. Seasonal changes of precipitation and air temperature in
South Kalimantan.
isms and plant roots, which produce CO2 . Therefore
precipitation generally enhances CO2 emission. In case
of tropical peatlands, however, raining emerges flooded
water on soil surface during wet season, not only in
paddy fields but also other fields in these peatlands, so
that the soil becomes anaerobic and no general trend in
CO2 could not be observed, while methanogenic bacteria
produce more CH4 . During dry season, the soil became
aerobic and methanogenic activity becomes low. Laboratory experiments by Moore and Dalva (1997) using
core samples taken from swamps and peat bogs in
Canada show that CH4 emission exhibited a negative
logarithmic correlation with the depth of the groundwater level whereas CO2 emission exhibited a positive
linear correlation with this depth. Such discrepancy
K. Inubushi et al. / Chemosphere 52 (2003) 603–608
607
Table 2
Effects of land use management on CO2 , CH4 and N2 O emission during 1 year. Numerical values are indicating the means of triplicates
and standard deviations
Site code
Location and land-use management
Total CO2 emission
(g C m2 y1 )
Total CH4 emission
(g C m2 y1 )
Total N2 O emission
(mg N m2 y1 )
G-1
G-2
G-3
Abandoned upland crops field
Abandoned paddy fields
Secondary forest
990 110
1540 290
1200 430
0.6 0.7
1.9 0.5
1.2 0.4
)110 82
)37 80
)51 44
between these reports may be caused by the difference in
the samplesÕ properties.
In case of N2 O, precipitation enhances both aerobic
nitrification and anaerobic denitrification trough enhanced microbial activities as shown in CO2 emission.
However once floodwater comes up on the soil surface,
highly soluble N2 O cannot be emitted easily to the atmosphere while further denitrified to N2 before emitted.
Similar phenomenon has been observed in temperate
paddy fields (Minami, 1997). Other factors such as
available C should be examined in relation to the dynamics of these gases.
3.3. Effect of land-use change in tropical peatland on
greenhouse gases
Based on the seasonal changes of CO2 , CH4 and N2 O
emissions from the peatlands, annual emission rate was
calculated (Table 2). Although not significantly different
due to large deviation, converting from secondary forest
peatland to paddy field tended to increase annual
emissions of CO2 and CH4 to the atmosphere (from 1.2
to 1.5 kg CO2 -C m2 y1 and from 1.2 to 1.9 g CH4 -C
m2 y1 ), while changing land-use from secondary forest
to upland tended to decrease these gases emissions (from
1.2 to 1.0 kg CO2 -C m2 y1 and from 1.2 to 0.6 g CH4 C m2 y1 ), but no clear trend was observed for N2 O
which kept negative value as annual rates at three sites.
We examined previous result about the effect of land-use
from secondary forest to paddy field in South Kalimantan on CO2 , CH4 and N2 O emissions based on
single measurement in November 1999 (Hadi et al.,
2001), and fond similar changes in CO2 and CH4 , but
not in N2 O which remained as positive higher values
than this study.
These findings confirmed our former results (Hadi
et al., 2000) that the tropical peatland can be a source or
a sink of N2 O; the land which was under oxic conditions
acted as a source and that which was under reductive
conditions acted as a sink. Controlling factors for N2 O
emission is still not clear even in the seasonal pattern
showed some trends. Converting natural peatland to
cultivated land can either increase or decrease the
emission of N2 O to the atmosphere depending on the
soil moisture. However in case of CO2 and CH4 , estimation rates can be reasonably accurate based on the
previous report. Further investigations are needed to
make the estimate of these greenhouse gases emission
more accurately, including year-to-year variations.
Acknowledgements
We acknowledge H. Arifin (professor of Soil Science
at Lambung Mangkurat University) for his valuable
comments, suggestions and help. The fieldwork in South
Kalimantan was possible by the help of Messrs. Hairil
Ifansyah, Sudirman and Fadly Razie (students and staff
of Lambung Mangkurat University). This work was
partly supported by the Grant from the Environmental
Agency, Japan.
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