Presented by Kristell Hergoualc’h, Senior Scientist, CIFOR, at "Online Webinar 2: Biophysical Attributes and Peatland Fires", on 14 October 2020 This presentation underlined existing gaps in data and knowledge on GHG emissions accounting for tropical peatland after restoration efforts. She also shared insights about how GHG emissions can arise from a range of human activities and microbial activities.

1. Monitoring tropical peatlands GHG emissions:
Is current scientific knowledge sufficient to identify
easily measurable and reliable proxies?
Kristell Hergoualc’h

2. Tropical peatlands
• Prominent role as a global C pool
350 Gt C in the soil only (Gumbricht et al 2017)
• In pristine peat swamp forests Indonesia
220 Mg C ha-1 in phytomass (Hergoualc’h & Verchot 2011)
670 Mg C ha-1 m-2 in peat (Warren et al 2012)
• Tremendous peat C stocks
Higher litter C inputs than decay losses in anoxic
conditions over long-term

3. (Drösler et al 2014)
N2O emissions: Peat decomposition + N application in
fertilized systems
CH4 emissions: Soil + ditches + fires
Peat GHG emissions

4. GHG emissions in tropical Southeast Asian peatlands
-40
-20
0
20
40
60
80
100
PristineF
DrainedF
Acacia
Oilpalm
Sagopalm
Cropland
Ricefield
Grassland
Rewetted
PeatGHGemissions
(tCO2eq/ha/y)N2O CH4 CO2 DOC CO2 on-site
24
77
44
12
57
50
41
5-1
• Pristine peat swamp forests
Small sink of GHG
On-site CO2 uptakes >
DOC exports, N2O, CH4
emissions
(Hergoualc’h and Verchot 2014)
• Much higher CH4 fluxes occur
in natural peatlands of
Amazon basin than in
Southeast Asia (Hergoualc’h et al
2020)
-5
0
5
10
15
20
25
30
Intact M
MgCO2eq.ha-1Y-1
Net CO2
CH4
N2O
27 ± 8

5. GHG emissions in tropical peatlands
• After drainage and
conversion
Large source of GHG
Dominance of CO2 over
other GHG, except in
shallow drained systems
(Sago) (Drösler et al 2014)
-40
-20
0
20
40
60
80
100
PristineF
DrainedF
Acacia
Oilpalm
Sagopalm
Cropland
Ricefield
Grassland
Rewetted
PeatGHGemissions
(tCO2eq/ha/y)
N2O CH4 CO2 DOC CO2 on-site
24
77
44
12
57
50
41
5-1
Fire and fertilized-induced N2O emissions
excluded

6. GHG emissions in tropical peatlands
• After drainage and conversion
IPCC emission factors based on very limited N2O flux data of
low magnitude while large emission rates have been
recorded since then (Oktarita et al 2017)
Emissions from forest degradation without drainage prove to
be large
- Indonesia
(Swails et al in prep)
-5
0
5
10
15
20
25
30
Intact Medium Deg. High Deg.
MgCO2eq.ha-1Y-1
Net CO2 CH4 N2O
21 ± 8 46 ± 427 ± 8
- Peru
(van Lent et al in prep)

7. GHG emissions in tropical peatlands
• After rewetting
Source of GHG
Based on assumptions (no
data):
CO2 on-site , N2O = 0
CO2 DOC, CH4 ≈ pristine
conditions (Blain et al 2014)
• After restoring?
No assessment, no data
-40
-20
0
20
40
60
80
100
PristineF
DrainedF
Acacia
Oilpalm
Sagopalm
Cropland
Ricefield
Grassland
Rewetted
PeatGHGemissions
(tCO2eq/ha/y)
N2O CH4 CO2 DOC CO2 on-site
24
77
44
12
57
50
41
5-1

8. Proxies for monitoring peat GHG fluxes in
the tropics
• Proxies typically derived from process-based modelling or more
empirical approaches. Both require solid, long-term and consistent
datasets
Ex. Soil C:N ratio to scale N2O emissions from drained forest histosols
to national levels in Sweden (Klemedtsson et al 2005)
• Difficulty in identifying generic proxies as
- Key controls of GHG fluxes may vary among land uses / drainage
practices
Ex. CH4 fluxes chiefly controlled by water table level in undrained
systems, but not in drained ones

9. Proxies for monitoring peat GHG
fluxes in the tropics
- Different processes are governed by different controls
CO2 on site = Heterotrophic respiration – Litter inputs
Ø Which would be the more suitable proxy for peat CO2 on
site emissions?
Ø Process-based modelling required
- Some key controls seldom reported e.g. soil mineral N
contents and dynamics

10. Take-home messages
• We need more peat GHG emissions and controlling factors data for
the tropics
Lacking: Pre-post rewetting / restoration data, data outside of
Southeast Asia
• We need good quality data
Tendency towards short term experiments with low measurement
frequency
• We need to process-based model peat GHG fluxes for enhanced
understanding of complex and interactive processes and adequate
identification of easily measurable and reliable proxies

11. Thank you
THANK YOU FOR YOUR
ATTENTION !