Kristell Hergoualc’h, N Dezzeo, LV Verchot, C Martius, J
van Lent, J Del Aguila Pasquel, M Lopez
Spatial and temporal variability of soil N2O
and CH4 fluxes along a degradation
gradient in a palm swamp peat forest in the
Peruvian Amazon
13th International Symposium on Biogeochemistry
of Wetlands, 24th March 2021

Peruvian peatlands
 Key contributor tropical peatlands
Gumbricht et al (201
 Amazonian peatlands mainly Mauritia
flexuosa-dominated forests (Draper et al. 2014)
 C-dense ecosystems (850 Mg C ha-1) (Draper et al. 2014)
 Recurrent degradation over 30 years: M. flexuosa
palms cut for fruit collection (Horn et al. 2018)
 73% M. flexuosa-dominated stands degraded in
pilot area (Hergoualc’h et al. 2017)

Objectives
 How do N2O and CH4 fluxes vary
spatially at the microscale and
macroscale under undegraded and
degraded conditions?
 How do the fluxes vary intra-annually
and inter-annually?
 How do environmental variables
control the spatial and temporal
variation of the fluxes?
Caballero Rodriguez

Experiment
Highly
deg.
Medium
deg.
Intact
 Iquitos, Northern Peruvian
Amazon
 Degradation gradient
I: Intact
mD: medium degradation
hD: high degradation
 3 years (including El Niño/La Niña episodes) monthly monitoring of:
→ Soil fluxes of CH4, N2O
→Environmental variables (rainfall, temperature, moisture, soil
mineral N content and dynamic)

Experiment
 Disaggregation by microtopography (hummock vs. hollow), and palm
status (live vs. cut)
 Degradation impacts on forest structure & soil microtopography
considered for site-scale assessments
0
50
100
150
200
250
Intact mDeg hDeg
M.
flexuosa
(#
ha
-1
)
Cut
Live
Live M. flexuosa Cut M. flexuosa
Hummock
size reduced
by 30%

Soil N2O fluxes
 Microscale
b, 2
a
0
2
4
6
8
10 Intact
b, 1
a
b
a
0
2
4
6
8
10 Medium Degradation
Live hummock Live hollow
Cut hummock Cut hollow
b, 2
a a
a
0
2
4
6
8
10 High Degradation
N2O hummock > N2O hollow (except for cut palms at hDeg)
N2O mDeg < N2O Intact, N2O hDeg for hummock live palm
 Macroscale
Site-scale emissions relatively steady over years
N2O mDeg (0.5) < N2O Intact (1.3), N2O hDeg (1.1) (kg N ha-1 y-1)
=> Heterogeneous soil WFPS fluctuations along the forest complex

Controls of soil N2O fluxes
 Water-filled pore space (WFPS)
 Water table level (WT)
 WT and Net
nitrification

Soil CH4 fluxes
a, 1
b, 2
0
250
500
750
1000
1250
Intact
b, 2
a, 1
b
a
Medium Degradation
Live hummock Live hollow
Cut hummock Cut hollow b, 2
a, 1
b
a
High Degradation
 Microscale
CH4 hummock < CH4 hollow at the Intact, opposite at degraded sites
CH4 Intact < CH4 degraded for hummock, opposite for hollow
 Macroscale
Site-scale emissions increased with
precipitation
No diff. in CH4 annual emissions among
sites (161-226 kg C ha-1 y-1)

Controls of soil CH4 fluxes
 Water table level (WT)
 Air temperature
 Soil net nitrification rate

Concluding remarks
 Impacts forest degradation on GHG emissions in tropical peatlands
→ Complex to monitor: Micro- to macro-scale & specific to degradation
type
→ Degradation altered micro-scale N2O and CH4 emissions, but site-
scale emissions were homogeneous among sites
→ Impact on peat C budget and ecosystem-level losses (Vegetation C
stocks + soil GHG changes) remain to be addressed
 Climate change impacts?
Projected greatest precipitation in the study area may foster CH4
emissions which is not considered in current modeling efforts (Wang et
al 2018)

Thank you! Questions?