Effect of plant-mediated oxygen supply and drainage on greenhouse gas emission from a tropical peatland in Central Kalimantan, Indonesia

Figures & data

Figure 1 Diagram of a closed cell for dissolved oxygen (DO) measurement. PVC, polyvinyl chloride.

Figure 2 Seasonal changes in precipitation (vertical bars) and water table level at each site (lines with symbols).

Table 1 Environmental factors at all study sites averaged for the observation period

Site	Description	Air temperature (°C)		pH		Electric conductivity (μS cm^−1)		Nitrate (NO3^−; mg N L^−1)		Ammonium (NH4^+; mg N L^−1)
FW1	Flooded forest site #1	28.2 ± 1.0^ab	(3)	3.6 ± 0.1^ab	(31)	85 ± 8^c	(31)	0.0565 ± 0.0492^a	(15)	0.0741 ± 0.0928	(15)
FW2	Flooded forest site #2	27.4 ± 1.2^a	(5)	3.6 ± 0.2^ab	(31)	86 ± 14^c	(31)	0.0519 ± 0.0319^a	(13)	0.143 ± 0.214	(13)
FD	Drained forest site	28.9 ± 1.5^ab	(5)	3.5 ± 0.1^a	(17)	125 ± 16^d	(17)	0.0781 ± 0.0325^ab	(9)	0.086 ± 0.130	(9)
BW1	Flooded burnt site #1	33.9 ± 4.0^c	(2)	3.7 ± 0.2^b	(31)	56 ± 10^b	(31)	0.260 ± 0.253^b	(15)	0.194 ± 0.491	(15)
BW2	Flooded burnt site #2	31.7 ± 2.2^bc	(4)	3.7 ± 0.2^b	(32)	50 ± 12^b	(32)	0.211 ± 0.219^ab	(15)	0.205 ± 0.263	(15)
BD	Drained burnt site	32.8 ± 1.4^c	(5)	4.0 ± 0.2^c	(28)	35 ± 5^a	(28)	0.0915 ± 0.0401^ab	(13)	0.061 ± 0.110	(13)

1. Values are means and standard deviations of environmental factors.

2. Numbers in parentheses represent sample size at each site.

3. Values within the same column with different lowercase letters differ significantly (P < 0.05; corrected by Bonferroni method).

Figure 3 Seasonal variations in the fluxes of (a) methane (CH₄), (b) carbon dioxide (CO₂) and (c) nitrous oxide (N₂O) at the ground surface. Error bars show standard deviations.

Figure 4 Relationship between water table level and the fluxes of (a) methane (CH₄), (b) carbon dioxide (CO₂) and (c) nitrous oxide (N₂O), averaged for the observation period. Error bars show standard deviations.

Table 2 Comparison of greenhouse gas (GHG) fluxes among different land use and drainage conditions.

Sites	Methane (CH4) flux (mg C m^−2 h^−1)		Carbon dioxide (CO2) flux (mg C m^−2 h^−1)		Nitrous oxide (N2O) flux (μg N m^−2 h^−1)		Global warming potential (GWP; CO2-eq mg C m^−2 h^−1)
Flooded forest sites (FW1 and FW2)	1.37 ± 2.03^a	(24)	195 ± 199^ab	(23)	−2.4 ± 16.9	(24)	208 ± 204^ab	(23)
Drained forest site (FD)	0.0084 ± 0.0321^a	(15)	340 ± 250^b	(15)	3.4 ± 19.2	(15)	340 ± 250^b	(15)
Flooded burnt sites (BW1 and BW2)	5.75 ± 6.66^b	(18)	198 ± 165^ab	(18)	−8.7 ± 41.9	(16)	249 ± 171^ab	(18)
Drained burnt site (BD)	0.220 ± 0.143^a	(15)	108 ± 115^a	(15)	8.1 ± 75.5	(14)	111 ± 113^a	(15)
Analysis of Variance (ANOVA)	df	F	df	F	df	F	df	F
Main factors and interaction
Land use	1	7.34**	1	6.33*	1	0.01	1	4.13*
Drainage	1	16.49**	1	0.36	1	1.23	1	0.00
Land use × Drainage	1	6.05*	1	6.64*	1	0.29	1	8.59**
Error	68		67		65		67
Simple main effects
Land use under flooded condition		15.85**		0.00		0.22		0.47
Land use under drained condition		0.03		11.30**		0.09		10.73**
Drainage in forest vegetation		1.36		5.32*		0.18		4.34*
Drainage in burnt area		20.05**		1.86		1.23		4.26*

1. Fluxes are shown in means ± standard deviations. Positive fluxes mean net emission from peat soil.

2. Numbers in parentheses represent sample sizes in each level.

3. Values within the same column with different lowercase letters differ significantly (P < 0.05; corrected by Bonferroni method).

4. Symbols * and ** mean P < 0.05 and P < 0.01, respectively.

Figure 5 Vertical distribution in dissolved concentrations of (a) methane (CH₄), (b) carbon dioxide (CO₂), (c) nitrous oxide (N₂O) and (d) dissolved oxygen (DO), averaged for each depth. Soil temperature preliminarily observed in 2011 was plotted with dissolved CO₂ (b). Error bars show standard deviations. For better identifiability, the depths in the profiles were slightly shifted from their actual depths (20, 40, 60 and 80 cm for CH₄, CO₂ and N₂O; 10, 20, 40 and 80 cm for DO; 5, 10, 30 and 50 cm for soil temperature).

Table 3 Results of three-way analysis of variance (ANOVA) on dissolved gas concentrations among different land use, drainage and depth

	Dissolved methane (CH4)		Dissolved carbon dioxide (CO2)		Dissolved nitrous oxide (N2O)		Dissolved oxygen (DO)
	df	F	df	F	df	F	df	F
Main factors
Land use	1	125.95**	1	8.54**	1	4.70*	1	4.87*
Drainage	1	28.25**	1	14.48**	1	4.73*	1	0.66
Depth	3	0.41	3	4.09**	3	1.96	3	0.20
Error	151		137		151		73
Interactions
Land use × Drainage	1	27.84**	1	47.98**	1	6.56*	1	0.62
Land use × Depth	3	0.50	3	6.70**	3	1.59	3	0.38
Drainage × Depth	3	5.26**	3	9.36**	3	1.57	3	1.31
Land use × Drainage × Depth	3	5.30**	3	1.67	3	1.95	3	0.31

Symbols * and ** mean P < 0.05 and P < 0.01, respectively.