Burnt Areas
Peat depth at the burnt areas ranges from 390 cm to 550 cm and is categorized as
very deep peat. Soil elevation at the burnt area ranges from 8.06 m to 9.47 m AMSL
(burnt area 1 to burnt area 3, respectively). The average GWL at the distance of 1 m
was À12 cm, at the area 2, to À35 cm at the area 1. The lowest GWL was found at
the distance of 350 m on the left side of canal, ranges from À77 cm to À93 cm
(Fig. 22.6). The average GWL on both sides of canal was not significantly different
( p > 0.05), even though GWL on the right side was slightly higher than that on the
left side, especially those further from the canal (>50 m).
In general, the burnt area as shown in Fig. 22.7 has similar average GWL. It is
worth noticing that the average GWL (À46 cm) on the right side of canal is slightly
higher than that on the left side (À54 cm). This pattern is similar to that of the
non-burnt areas (Fig. 22.4 above). Our findings show that canal blocking may have
increased GWL, close to the level where the peatlands are not influenced by the canal
(area adjacent to the road, i.e. the right side). This phenomenon was observed in both
the non-burnt and burnt areas of our research site.
Further areas from the canal, both on the left and right sides, have lower GWL
than the areas closer to the canal. This may have been influenced by the fact that
higher peat elevation is located in the further sites from the canal (Fig. 22.8).
Significant correlation was found between distance from canal, peat elevation, and
GWL ( p < 0.05), where further distance from the canal corresponds to higher
elevation of peat surface and lower GWL. Other environmental variables that may
influence this phenomenon may be other biophysical properties, such as hydraulic
conductivity, macroporosity, bulk density, or fiber content (Hirano et al. 2014;
Kurnianto et al. 2019), which are beyond the scope of this study.
22.3.2 Fires and Groundwater Level (GWL)
There was a significant correlation between the average GWL and fires (P < 0.01)
(Fig. 22.9). Fire increases the average GWL by 11 cm, from À61 cm to À50 cm
below the peat surface. Fire occurring in peatlands had depleted the plant biomass
above the soil surface and burned several centimeters of the peat's top layer (Page
et al. 2011). In the areas where frequent fire occurred, more peat had burned,
rendering higher GWL than the one in the non-burnt areas.
The average GWL in the burnt areas shown in this study (À50 cm) is higher than
that shown by Wakhid et al. (2019), which showed the average GWL in the burnt
area at À75 cm. This may suggest that the canal blocking in our burnt sites had
enabled the GWL to increase substantially, i.e. 25 cm. However, the different sites
and methods between both studies may infer this increased figure of GWL. Hirano
et al. (2014) reported that the number and size of different burning areas will result in
changes on the physical, chemical, and microbiological characteristics of the peat,
which will indirectly affect the dynamics of the GWL.
22 The Effect of Fire and Rewetting on the Groundwater Level in Tropical Peatlands
619
Peat depth at the burnt areas ranges from 390 cm to 550 cm and is categorized as
very deep peat. Soil elevation at the burnt area ranges from 8.06 m to 9.47 m AMSL
(burnt area 1 to burnt area 3, respectively). The average GWL at the distance of 1 m
was À12 cm, at the area 2, to À35 cm at the area 1. The lowest GWL was found at
the distance of 350 m on the left side of canal, ranges from À77 cm to À93 cm
(Fig. 22.6). The average GWL on both sides of canal was not significantly different
( p > 0.05), even though GWL on the right side was slightly higher than that on the
left side, especially those further from the canal (>50 m).
In general, the burnt area as shown in Fig. 22.7 has similar average GWL. It is
worth noticing that the average GWL (À46 cm) on the right side of canal is slightly
higher than that on the left side (À54 cm). This pattern is similar to that of the
non-burnt areas (Fig. 22.4 above). Our findings show that canal blocking may have
increased GWL, close to the level where the peatlands are not influenced by the canal
(area adjacent to the road, i.e. the right side). This phenomenon was observed in both
the non-burnt and burnt areas of our research site.
Further areas from the canal, both on the left and right sides, have lower GWL
than the areas closer to the canal. This may have been influenced by the fact that
higher peat elevation is located in the further sites from the canal (Fig. 22.8).
Significant correlation was found between distance from canal, peat elevation, and
GWL ( p < 0.05), where further distance from the canal corresponds to higher
elevation of peat surface and lower GWL. Other environmental variables that may
influence this phenomenon may be other biophysical properties, such as hydraulic
conductivity, macroporosity, bulk density, or fiber content (Hirano et al. 2014;
Kurnianto et al. 2019), which are beyond the scope of this study.
22.3.2 Fires and Groundwater Level (GWL)
There was a significant correlation between the average GWL and fires (P < 0.01)
(Fig. 22.9). Fire increases the average GWL by 11 cm, from À61 cm to À50 cm
below the peat surface. Fire occurring in peatlands had depleted the plant biomass
above the soil surface and burned several centimeters of the peat's top layer (Page
et al. 2011). In the areas where frequent fire occurred, more peat had burned,
rendering higher GWL than the one in the non-burnt areas.
The average GWL in the burnt areas shown in this study (À50 cm) is higher than
that shown by Wakhid et al. (2019), which showed the average GWL in the burnt
area at À75 cm. This may suggest that the canal blocking in our burnt sites had
enabled the GWL to increase substantially, i.e. 25 cm. However, the different sites
and methods between both studies may infer this increased figure of GWL. Hirano
et al. (2014) reported that the number and size of different burning areas will result in
changes on the physical, chemical, and microbiological characteristics of the peat,
which will indirectly affect the dynamics of the GWL.
22 The Effect of Fire and Rewetting on the Groundwater Level in Tropical Peatlands
619