Presented by Erin Swails at 13th International Symposium on Biogeochemistry of Wetlands, "Wetlands in a Changing Climate" on 24 Mar 2021

1. Erin Swails, Kristell Hergoualc’h, Louis Verchot, Nisa Novita, Deborah Lawrence
March 24, 2021
13th International Symposium on Biogeochemistry of Wetlands
Baton Rouge, Louisiana, USA
Contributions of CH4 and N2O to peat GHG
emissions from forest and oil palm
plantations in an Indonesian peatland

2. Tropical peatlands store vast amounts of soil carbon
• Global extent: 90 - 170 Mha (Gumbricht
et al. 2017)
• Total soil carbon: 136 Gt C (Müller and
Joos 2020)
• SE Asia holds most extensive and
deepest tropical peatlands (Gumbricht et
al. 2017)

3. SE Asian peatlands experienced rapid land-use conversion 1990 - 2015
Miettinen et al. 2016 Global Ecology and Conservation

4. Indonesian peatlands are a large and growing source of GHG emissions
• How do peat CH4 and N2O emissions differ between and within OP and forest?
• How do peat GHG budgets differ between OP and forest and between forest types?
Deforestation Burning Oil Palm Plantation
Drainage
Peat Forest
b
CO2 CH4 N2O
CO2 CH4 N2O
?
?
? ?

5. Sampling design
• Permanent plots in forest (n=3) and smallholder
oil palm plantations (n=3) on peat
• 6 subplots per plot
• Near/far and hummock/hollow measurements

6. Monthly measurements
• Monitoring period: Jan 14 – Jun 15 + Sep 15
• CH4, N2O, water table depth, soil moisture, soil and
air temperature
• Soil respiration → Net peat CO2 budget
• Peat chemistry: C, N, NO3
-, NH4
+
• One year with normal precipitation (2014), and one
El Niño year (2015)

7. Variation in physical controls Jan 2014 – Sep 2015
Total
precipitation,
mm
oil palm
forest
oil palm < forest
p = 0.04
Swails et al. 2021 Biogeochemistry
80
70
60
50
40
Soil
water-filled
pore
space,
%
oil palm < forest
p = 0.01

8. Peat CH4 emissions were high in forest and insignificant in oil palm
Swails et al. 2021 Frontiers in Environmental Science
Water table level, cm
CH
4
+
2
mg
m
-2
d
-1
Forest
R2=0.49
p<0.0001
% WFPS
CH
4
mg
m
-2
d
-1
Oil palm
R2=0.51
p=0.02
Forest
OP
forest > oil palm
p < 0.0001

9. Peat N2O emissions were similar in forest and oil palm
N
2
O
mg
m
-2
d
-1
Forest
OP
Swails et al. 2021 Frontiers in Environmental Science
Water table level, cm
Forest
R2=0.28
p=0.02
N
2
O
mg
m
-2
d
-1

10. Cumulative CH4 and N2O fluxes in forest and oil palm
Land use Plot CH4 (kg ha-1 yr-1) N2O (kg ha-1 yr-1)
Forest Average 14.0 ± 2.8 a 5.2 ± 3.7
FOR-1 18.7 ± 5.1 12.6 ± 1.1 α
FOR-2 14.3 ± 10.5 2.3 ± 0.4 β
FOR-3 9.0 ± 2.6 0.6 ± 0.7 β
Oil Palm Average 0.3 ± 0.4 b 5.0 ± 3.9
OP-2011 -0.3 ± 0.4 12.7 ± 3.8 α
OP-2009 0.2 ± 0.9 1.1 ± 0.6 β
OP-2007 1.0 ± 0.8 1.1 ± 0.1 β
Swails et al. 2021 Frontiers in Environmental Science
N
2
O
kg
ha
-1
yr
-1
Soil C content, %
R2=0.8
p=0.02

11. Peat GHG budgets in forest and oil palm
• In OP 96% of emissions were released as CO2; in forest CH4 and N2O contributed 65%
of the GHG budget
• GHG emissions were 8 times higher in OP than forest
Secondary Forest Primary
Forest
Forest Oil palm Difference
OP-Forest
(Mg C ha-1 yr-1)
Litterfall 5.8 ± 0.6 5.3 ± 0.6 5.5 ± 0.8 1.1 ± 0.2
Roots 1.5 ± 0.8 1.5 ± 0.8 1.5 ± 0.8 3.6 ± 1.1
Total soil C inputs 7.3 ± 1.0 6.8 ± 1.0 7.0 ± 1.1 4.7 ± 1.1
SRh 8.2 ± 0.7 6.1 ± 0.3 6.8 ± 0.6 12.0 ± 2.0
DOC 0.6 ± 0.0 0.6 ± 0.0 0.6 ± 0.0 0.9 ± 0.1
Total soil C outputs 8.8 ± 0.7 6.7 ± 0.3 7.4 ± 0.6 12.9 ± 2.0
Peat C budget 1.4 ± 1.2 -0.1 ± 1.1 0.4 ± 1.3 8.3 ± 2.3
(Mg CO2e ha-1 yr-1)
CO2 budget 5.2 ± 4.4 -0.5 ± 3.9 1.4 ± 3.9 30.4 ± 8.5 28.9 ± 9.7
CH4 1.6 ± 0.5 1.0 ± 0.2 1.2 ± 0.2 0.0 ± 0.0 -1.2 ± 0.2
N2O 3.4 ± 0.8 0.4 ± 0.2 1.4 ± 1.0 1.3 ± 1.0 -0.1 ± 1.4
Peat GHG budget 10.2 ± 4.5 0.9 ± 3.9 4.0 ± 4.8 31.7 ± 8.6 27.7 ± 9.8
(%CO2, CH4, N2O) (51, 16, 33) (-51, 109, 42) (35, 30, 35) (96, 0, 4) (104, -4, 0)

12. Thank you
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