39

The Impact of Surface Fires on Peatland in
the Land Preparation Area belong to the Community
Bambang Hero SAHARJOForest Fire Laboratory, Division of Forest Protection,
Department of Silviculture, Faculty of Forestry, Bogor Agricultural University,
Bogor 16001, West Java, Indonesia,
e-mail: bhsaharjo@gmail.com

Abstract
It is well known that at least 20 million of Indonesia’s people were directly or indirectly affected by the
1997/1998 Indonesian forest and field fires, where 10-11 million acres of forest and fields burnt. Haze
contains many air pollutants such as CO, CO2, SO2, NO(x) and NH4. These and bacteria caused thousands ofpeople in Riau, Jambi, South Sumatra, and Central, West and East Kalimantan to be hospitalized, with 527
fatalities in a mere three months. It has also been found that 80% to 90 % of the Indonesian fires resulted fromestate crops and industrial forest plantations as the result of actions by companies and communities. The
communities claimed that using fire in land preparation is cheap, easy and quick, but unfortunately the facts
are not clear from much scientific evidence.
In order to determine the impact of peatland fires started by communities during land preparation, an
experimental land preparation using fire in peatland was conducted in a village area in Pelalawan, Riau
Province, Sumatra. The main objective of the research was to evaluate the response of the ecosystem,
including greenhouse gas emissions released by the fires used for land preparation for agricultural purposesby the community. The results of the research show that factors such as fuel load, fuel bed depth and watertable performance are critical to the degree of peat destruction and ultimately affect green house gas (GHG)
emissions released during burning.
Key words: fires, GHG, land preparation, peat, Riau, Sumatra

1. Introduction
Transboundary haze pollution due to the smoke fromland preparation using fire has become a big problem inIndonesia every year, especially when the dry season
comes, since ten years ago. It has been found that most of
the smoke originates from illegal land preparation fires inoil palm and industrial forest plantations (60%-80%) as
well as from shifting cultivation, which, unfortunately, isusually blamed for the smoke (Saharjo, 2007). It is wellknown that when fires broke out in many provinces inIndonesia, many people blamed shifting cultivation as
the cause of them, because communities were using fire
for land preparation for agricultural purposes. People
engaging in shifting cultivation used fire for their land
preparation, because it was cheap and easy to do, and it
had been done for thousands years (Goldammer, 1993)
with no environmental problems like those happening
now. Shifting agriculture systems in their early practiceand extended use were possible largely due to low humanpopulation pressure on the forest resources. They provided a sustainable base of subsistence for indigenous
forest inhabitants, and their patch impacts had little
Global Environmental Research
15/2011: 39-44
printed in Japaneffect on the overall forest ecosystem stability (Nye &Greenland, 1960).
Humans probably had a role in starting forest fires inrecent millennia, and may have deliberately burned forest
to improve hunting for thousands of years (Qadri, 2001).
As prehistoric human settlers of the Indonesian archipelago began to switch from hunting and gathering to growing crops, they used fire to clear agricultural plots in theforest. The cycle of forest clearing, cultivation and abandonment is known as swidden, kaingin or shifting cultivation, an agricultural system adopted throughout mostof the region over a period of thousands of years.
Swidden cultivation has continued into this century inlocations where soils are too poor to support permanentcultivation of annual crops.
Smoke problems, especially those resulting from
community activities, should be reduced but they cannot
be directly postponed or prohibited, because previous
experience has shown that banning the use of fire forpreparation of land belonging to communities results inmore fires and damage (Saharjo & Husaeni, 1998).
Accordingly, they still may use fire for their land preparation but under controlled conditions, especially with©2011 AIRIES40

B. H. SAHARJO

regard to smoke problems, which have been implicated inemissions of trace gases produced during burning. One ofthe promising solutions is a burning method producing
less smoke. This low-smoke burning method is prescribed burning which produces less smoke.
Smoke management strategies for prescribed burning
consist largely of conducting fire under specified fuelloading, fuel moisture regimes and meteorological conditions, and specifying ignition techniques that maintainthe smoke’s environmental impact within acceptable
limits (Debano et al., 1998). Smoke management practices include reducing fuel loads, improving combustion
efficiency, igniting fires effectively and mopping-up
efficiently. The specific practices used in a locality or
region depend largely on the fire management objectives
to be satisfied and the types of fuel to be burned (Debano
et al., 1998). Prescribed burns conducted when small fuelmoisture is low, large fuel moisture is high, and forest
floor moisture is high also substantially reduce emissions
by making less fuel available for combustion. Prescribedfires can have a wide range of particulate emissions factors, with magnitudes of these factors depending onwhether the fire is dominated by flaming combustion orsmoldering. Smoldering fires have the greatest emissions
factors for nearly all combustion products (Debano et al.,1998). Avoidance of potential smoke problems isachieved by scheduling burning during the season whenfuel moisture and meteorological conditions are likely toresult in reduced smoke emissions or involvement ofurban areas. Dilutions involve controlling emission rates
by fire management techniques or scheduling prescribedfires for when atmospheric processes favor unstableconditions and therefore maximum mixing of the lower
atmosphere. A key to good smoke dilution and dispersal
is accurate weather forecasts of wind speed and direction,
atmospheric stability and mixing heights (Debano et al.,1998).
The purpose of the present research was to determine
the impact of using fire in land preparation areas belonging to a community on the peatland surface area, including greenhouse gas emissions released during burning.

2. Study Area and Method
2.1 Study area
Research was conducted in the period of August 2001
through July 2002 in a peatland area dominated by Sapric
belonging to the community of Pelalawan Village,
Pelalawan Sub-district, Pelalawan District, Riau Province. Based on survey results and information in theirbook about the land site, with maps and soil information,
Solok and Pekanbaru (1997) stated that the research site
in Pelalawan District was dominated by peat and included in the ‘peat dome’ physiographical group. 97.1 %of the site was located on 0%-8% slopes, while the rest
was located on slopes of 8%-15%.
The climate in Pelalawan District cannot be distinguished from that of Riau Province, generally being
tropical with an annual rainfall ranging from 2,500 to

3,000 mm with daily temperatures between 22°C and
31°C. According to data from the Meteorological andGeophysical Agency, Ministry of Transportation, theannual rainfall in the period between January andDecember 2001 at the site was 3,794.5 mm, accounted
for by 86 rainy days.
A vegetation analysis showed that the research site
was dominated by shrubs and ferns, the trees found included Shorea macrophylla, Macaranga pruinosa, Ficus
sundaica, Stenochlaena palustris, Parastemon uruphyllus, Baccaurea pendula, Nephorlepis flaccigera and
Gleinchenia linearis.
2.2 Methods: plot establishment and field
experiments
Before burning, three plots of 400 m2 (20 m x 20 m)
each surrounded by a one-meter canal with a depth of
1.5 m were set up at a Sapric peat site located oncommunity land in Pelalawan, Riau, Indonesia (Fig. 1).
In each plot, three sub-plots of 2 m2 were established andchosen randomly for the estimation of fuel load, fuel bed
depth and fuel moisture. Another sub-plot of the same
size was selected for estimating the rate of spread of thefire, flame height, flame temperature and peat destruction
through heat penetration.
Before slashing and burning were conducted, environmental conditions (temperature, relative humidity andwind speed) were measured, and fuel and peat characters
were identified. Following those activity, slashing was
conducted where big logs (diameter of more than 10 cm)
were removed from the plot. The slashed logs andbranches were separated throughout the plot and dried
under the sun for about three weeks.
After three weeks, when the slash and small logs had
dried, the entire plot was burned using the ring method,which is the technique usually used by the community toburn dried logs and branches. Burning was started under
one command and proceeded in a clockwise direction,with a bamboo torch used as the source of fire. The fire
was allowed to spread naturally in the subplot, finallyending in the middle of the ring with no fire jumping to
non-target areas. Through this technique the community
needed no help from other groups because they could
handle the fire by themselves, i.e., to burn one hectare,
only three persons were needed. During burning, the fire
behavior (rate of the spread of fire, flame length, flame
temperature) was monitored and recorded using a handy
camera, and greenhouse gas emissions were taken at
different stages of combustion (flaming, smoldering andglowing) using a handy pump. Burning was done in theafternoon in the period of 13.00 to 17.00 p.m. using atorch made from bamboo filled with gasoline. Immediately following the burning, the fuel left in all plots wasmeasured.
2.3 Estimations of fuel load, fuel bed depth and fuelmoisture
2.3.1 Estimation of fuel load
All vegetation found in the sub-plot in each plot,

The Impact of Surface Fires on Peatland in the Land Preparation Area belong to the Community

41

including shrubs, seedlings, saplings, poles and trees
were cut down and the understorey was slashed. Afterslashing was accomplished, the debris was dried under
the sun for three weeks as was usually done by the community. To estimate the fuel load, three sub-plots of 2 m2
(2 m x 1 m) were set aside in the plots (Fig. 1). The
amount of plant materials both living and dead in the
sub-plots were collected and weighed following the three
weeks of drying.

perpendicular to the moving flame front per minute,using a stop watch and tape and supported by the resultsof video camera recording.

2.3.2 Estimation of fuel moisture
The fuel load moisture content was calculated byobtaining three samples of 100 grams each of materials
found in the subplots (litter, leaves, branches and logs)
that were taken and used as samples for moisture content
measurements. The samples were put in an oven anddried for 48 hours at 75°C (Clar & Chatten, 1954). The
fuel moisture content was estimated on a dry weight basis.
The peat moisture was calculated by obtaining threesamples of 100 grams of peat found in the subplots andusing them as samples for moisture content measurements. The samples were put in an oven and dried for 48
hours at 75°C (Clar & Chatten, 1954). The peat moisture
content was estimated on a dry weight basis.

2.5 Smoke sampling during burning
Smoke samples were collected by using a portablepump connected to a vacuum plastic. Smoke was taken at
different phases of the combustion processes during
burning, namely flaming, smoldering and glowing. Gases
in the vacuum plastic were transferred to a vacuum bottle
which was then sent to the Greenhouse Gas Laboratory of
the National Institute for Agro-Environmental Science,
Tsukuba, Japan for further analysis. The gases analyzed
were CO, CO2, N2O and CH4.

2.3.3 Estimation of fuel bed depth
The fuel bed depth was measured by the averageheight of dried fuel that was spread out in each subplot.
2.4 Estimation of flame temperature, rate of spreadof fire and flame height
2.4.1 Estimation of flame temperature
The flame temperature at 0 m above soil and 1 cm
below the ground were measured using temperature sensors (thermocouples) and recorded using a data logger.
The temperature sensors were placed in each subplot at
two locations.
2.4.2 Estimation of the rate of spread of fire
The rate of spread of the fires when the surface wasburning was measured by the average distance traveled

2.4.3 Estimation of flame length
It was very difficult to measure the average flame
length directly in the burning condition, so the flame
length was calculated using scaled bamboo and supported by video camera recording.

2.6 Follow-up after burning
Following burning, the burnt fuel percentage wasestimated by identifying, collecting and segregating
burnt materials based on their own fuel characteristics(litter, branches and logs) in the subplots.
Peat destruction due to the surface fire was estimatedthrough heat penetration, which usually burnt the peatand blackened it.
2.7 Fire intensity
The fire intensity was calculated using Byram’s
equation (Chandler et al., 1983), FI=273 (h) 2.17, where:
FI is fire intensity (kW/m), and h is flame length (m).
2.8 Data analysis
For statistical analysis, a completely random designof variance was used to test for differences among subplots, based on the following model (Steel & Torrie,1981): Ymn = U + Tm + Emn, where Ymn = fuel and fire
behavior parameter at subplot m in replication n, U = themean of the treatment population sampled, Tm = treatment (slashing, drying, burning) and Emn = the random
component. To detect significant differences in fuel andfire behavior parameters among the subplots (p≤0.05),
the Duncan test was used (Steel & Torrie, 1981).

3. Results

Fig. 1 Sampling plots in the field experiment.

After being slashed and dried, the highest fuel loadfound was 132.3 ton/ha in the third subplot. The total fuelload in the other subplots varied from 110.83 ton/ha toTable 1 Fuel load before burning (tons/ha).
Plot
1
2
3

Litter
(20.83±1.44)a(23.30±7.63)a(22.50±2.50)a

Branches(40.83±23.22)b(32.33±8.74)a(36.37±13.77)ab

Logs(57.50±2.50)a(55.17±10.78)a(73.17±18.37)b• Different letters following standard errors indicate significantly different means (p≤0.05).

Total( 119.17±24.66)a(110.83±23.50)a(132.33±25.64)b

42

B. H. SAHARJO

119.17 ton/ha (Table 1). The fuel bed depth in the second
subplot was the shallowest at 82.8 cm, and differed significantly from those of the other subplots, while thegreatest depth was found in the first subplot at 100 cm(Table 2). The fuel load with the highest fuel moisture
content following slashing was logs in the third subplot at
34.14 %, while the lowest was dry leaves in the second
subplot at 9.54 % (Table 3). The peat moisture varied
from 201.29% to 330.05% and differed significantly(Table 4). During burning it was found that rate of spreadof the fires was highest in the third subplot at 1.11
m/minute, and the lowest in the first subplot at 0.47
m/minute (Table 5). The flame length was highest in thethird subplot at an average of 3.09 m, and the lowest in
the first subplot at 1.56 m (Table 5). The flame temperaTable 2 Fuel bed depth in the subplot.
Plot
1
2
3

Depth (cm)(100.0±39.96)b(82.8±21.3)a(98.4±47.3)b• Different letters following standard errors indicate significantly different
means (p≤0.05).

Table 3 Fuel moisture content before burning (%).
Plot
1
2
3

Leaves(11.73±1.41)a(9.54±1.88)a(9.85±1.97)a

Branches(18.85±2.29)a(19.19±4.43)a(19.74±3.03)aLogs(31.62±0.53)a(30.31±5.10)a(34.14±1.39)a• Different letters following standard errors indicate significantly different
means (p≤0.05).

ture at the ground (peat surface) in the third subplot was
1,000°C. This temperature was the highest, while thelowest was in the first subplot at 800° (Table 5). The
highest fire intensity, 1830.55 kW/m, was recorded in thethird subplot. It was differed significantly from those of
the other subplots (Table 5).
Burnt litter (leaves) in the subplots varied from
5.9 tons in the first subplot to 8.9 tons in the third subplot,
burnt branches varied from 8.5 tons in the first subplot to
14.8 in the third subplot, and burnt logs varied from
1.6 tons in the first subplot to 3.4 in the second subplot(Table 6). The depth and size of burnt peat varied in each
subplot. The deepest burnt peat surface among thesubplots was that of the second subplot at 31.87 cm withan area of 7 m2 which was equal to 1.75% of the area
burnt. The shallowest was 12.72 cm in the fourth subplot
with an area of 22 m2 which was equal to 5.5 % of thearea burnt (Table 7).
CO2 emissions during the flaming stage were found torange from 1,046 to 2,039 ppm; during the smoldering
stage, from 3,985 to 5,681 ppm; and during the glowing
stage, from 736 to 9,958 ppm (Fig. 2). CO emissions
during the flaming stage were found to range from 149
to 172 ppm; during the smoldering stage, from 255 to
801 ppm; and during the glowing stage, from 297 to
470 ppm (Fig. 3). CH4 emissions during the flaming stage
ranged from 11.3 to 40.5 ppm; during the smoldering
stage, from 15.5 to 113.2 ppm; and during the glowing
stage, from 24.9 to 61.6 ppm (Fig. 4). N2O emissions
during the flaming stage ranged from 367 to 435 ppb;
during the smoldering stage, from 526 to 853 ppb; andduring the glowing stage, from 405 to 594 ppb (Fig. 5).

Table 4 Peat moisture content at the site.
Parameter
Moisture content (%)

Plot 1(201.29±74.63)aPlot 2(234.23±30.26)b

Plot 3(330.05±78.41)c• Different letters following standard errors indicate significantly different means (p≤0.05).

Table 5 Weather conditions and fire behavior parameters during burning.
Parameter
Weather condition
Temperature (°C)
Relative humidity (%)
Wind speed (m/sec.)
Fire behavior
Fuel load (tons/ha)
Fuel moisture (%)
LeavesBranches
Logs
Flame length (m)Fire int. (kW/m)Rate of spread(m/mnt)
Flame temp. (°C)
1 cm below ground
GroundSlope (%)
Plot size (ha)Duration (min.)Burning time

Plot 1Plot 2Plot 3

38
55
0.41

38
50
1.09

39
49
1.07

(119.17±24.66)a(110.83±23.5)a(132.33±25.64)a(11.73±1.41)a(18.85±2.29)a(31.62±0.53)a(1.56±0.52)a(792.96±572.40)a(0.47±0.15)a(9.54±1.88)a(19.19±4.43)a(30.31±5.10)a(2.11±0.26)ab(1401.61±355.17)ab(0.99±0.26)ab(9.85±1.97)a(19.74±3.03)a(34.14±1.39)a(3.09±1.07)b(1830.55±634.74)b(1.11±0.32)b

70
800
0
0.04
22.13
11.22 a.m.

90
985
0
0.04
21.30
13.43 p.m.

95
1000
0
0.04
28.10
14.54 p.m.

• Different letters following standard errors indicate significantly different means (p≤0.05).

The Impact of Surface Fires on Peatland in the Land Preparation Area belong to the Community

4. Discussion

Table 6 Burnt fuel volume (tons).
Plot
1
2
3

Litter (leaves)
(5.9)
(7.6)
(8.9)

Branches(8.5)(11.5)(14.8)

Logs
(1.6)
(2.1)
(3.4)

Table 7 Burnt peat depth and area.
Plot
1
2
3

Depth (cm)
18
31.87
15.44

Burnt area (m2)
12
7
17

43

Percentage (%)
3
1.75
4.25

Fig. 2 CO2 emissions (ppm) during combustion stages.

Fig. 3 CO emissions (ppm) during combustion stages.

Fig. 4 CH4 emissions (ppm) during combustion stages.

Fig. 5 N2O emissions (ppb) during combustion stages.

The three weeks of drying the fuel load in the subplots
drastically changed the fire potency. The driest fuelmoisture in all of the subplots varied from 9% to 11%.
This driest fine fuel moisture is important because thefine fuel will be burnt as the first fuel. Drying of vegetation following slashing is practiced in Pelalawan before
they burn it from the land. In practical application thisdrying makes the spread of fire relatively uniform. It also
allows them to control the area easily and prevent the firefrom spreading to non-target sites. Unburned portions of
the field create significant problems for them when thesite is planted, because those areas are usually the best
breeding places for pests and diseases. The fuel bed depth,
which varies from 98.4% to 100%, is one of the mostimportant factors in causing different flame lengths,
which results in different fire intensities and also has
different penetration impacts that are linked with peat
destruction. The degree of heat penetration also depends
on the magnitude of the flame temperature resulting fromthe surface fire. Flame temperatures varying from 800oC
to 1,000oC in the ground that have heat penetration below
ground varying from 70-95 cm due possibly to the highpeat moisture, that varies from 201.29% to 330.05%.
During the experiment conducted in each subplot, theweather conditions did not differ significantly. Air temperatures varied from 38°C to 39°C; the relative humidity,
from 49% to 55%; and the wind speed, from 0.41 m/
minute in the first subplot to 1.09 m/minute in the second
subplot. The role of wind speed was very importantduring burning because all the subplots had 0% slope. It
was found that the rate of spread of the fire was highest in
the third subplot at 1.11 m/minute; the flame height was
3.09 m; and the flame temperature, 1,000°C. In addition,
more time was needed in the third subplot to complete theburning, at 28.1 minutes. The measurements and calculations also indicated that the third subplot had thehighest fire intensity recorded at 1,830.55 kW/m. The
high fire intensity reached in the third subplot may havebeen due to the fuel bed depth and high flame length. The
maximum peat area destroyed was in the second subplot,
with 7 m2 burnt due to heat penetration during burning,which reached 31.87 cm. The shallowest depth, 12.72 cm,
was in the fourth subplot with a burnt area of 22 m2. Thismeans that controlled burning can be conducted safely
and the fire prevented from jumping over to non-target
areas. How the worst peat destruction occured during thefires actually depended on how much fuel load was burnton the surface, which produced heat that could havepenetrated into the peat, and that was affected by the peat
type and its characteristics, i.e., moisture content of thepeat surface. This means that peat destruction can beprevented through higher moisture content in peat, whichin this case came from the water canal that surrounded
the area. Another important factor is the drying processes
at the surface of the peat, which determine how muchgreenhouse gases are emitted during burning. If the fuelload at the surface is relatively dry then the greenhouse

44

B. H. SAHARJO

gases emitted are not so big due to the fire being
dominated by the flaming stage. Unfortunately, if theconditions for drying the fuel are not so good then more
greenhouse gases will be emitted.
CO2 emissions are quite high and mostly depend on
the characteristics of the fuel left and the peat itself. The
proportion of the total combustion processes which makeup each stage is mainly controlled by the physicalattributes of the fuel and to a lesser degree by the weather
during the fire (Scholes et al., 1996). In the first plot,
glowing stage produced more CO2 than the smolderingand flaming stages, while in the second and third plot the
maximum was found at the smoldering stage. More CO
emissions were produced during the glowing stage in thefirst and second plots compared to the flaming andsmoldering stages. Carbon monoxide (CO) is commonly
produced with incomplete combustion of moist fuels, andhigh emissions of CO have been measured in the fire lineof relatively low-intensity fires (Sanberg et al., 1975),with the amount of CO emitted by the fire being a function of combustion efficiency, increasing as efficiencies
drop (Debano et al., 1998). Methane (CH4) emissions
were higher during the glowing stage than smolderingand flaming in the first plot, while in the second plot they
were higher in the flaming stage and in the third plot, atsmoldering stage. N2O emissions in the first plot werehigher in the smoldering stage, while in the second andthird plots they were higher in the smoldering stage. BothNO and NO2 are reactive gases that are emitted during
combustion (Lobart & Warnatz, 1993). NO is a thermallystable product of combustion. Although NO2 is less stable than NO, its abundance increases in smoldering fires(Clements & McMahon, 1980). Drying also determines
the time needed for burning the materials, and this has
implications for peat destruction and suppression activities. In order to let the fire spread naturally with minimal
impact and less peat destruction, it is recommended toleave only small diameter (< 5 cm) logs (branches) for
burning and make sure that the materials are dried withnot more than 10% moisture content. If this is accompanied by an effective burning technique it will also reduce
the smoke produced during burning.
Controlled burning especially by the local people canbe used as one method of land preparation using fire as it
is guaranteed by the law. Low impact from burning canbe achieved through proper activities conducted before
and during burning. Activities that can be conducted
before burning include fuel selection, slashing and drying.
Drying the fuel load at the surface for at least two to three
weeks will reduce the fuel moisture content and make therate of the spread of the surface fire relatively uniform,
limiting the danger of wildfire occurrence. Anotherimportant factor is the role of water from canals that
could protect the peat from heat penetration, thus preventing peat destruction by increasing the water table inthe canal.

Acknowledgment
The author wishes to express special thanks to theEnvironmental Department of PT. Riau Andalan Pulp
And Paper (PT.RAPP), which funded the research andthe Greenhouse Gas Team of the National Institute forAgro-Environmental Science (NIAES), Tsukuba, Japanfor their greenhouse gas analysis.
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Bambang Hero SAHARJOBambang Hero SAHARJO is a Profesor of Forest
Protection at the Faculty of Forestry, Bogor
Agricultural University (IPB), Indonesia. He isinterested in various aspects of environmental
science ranging from forest protection, forest
fires, environmental destruction, emissions
reduction and climate change. He has M.S. and Ph.D. degrees from Kyoto
University. He has also served as Editor-in-Chief of the Indonesian
Agricultural Science Journal and Journal of Tropical Silviculture. He has
authored many publications on forest fires, environmental destruction andforest protection.

(Received 30 January 2011, Accepted 26 September 2011)