Carbon balance in a heterogeneous
cutover bog in the Jura Mountains.
Estelle Bortoluzzi,
Daniel Epron,
Daniel Gilbert,
Alexandre Buttler
WP 02: Carbon sequestration by peatland vegetation
Objectives
1. Identify and compare the vegetation communities colonizing abandoned cutover mire sites
2. Determine effects of key plant species used in peat restoration on carbon
sequestration
3.
Determine net primary production and biomass accumulation
4. Estimate net ecosystem productivity from seasonal determinations of
photosynthesis and respiration in a transparent enclosure
WP 02: Carbon sequestration by peatland vegetation
Milestones:
M3: Site selection for survey and setting up of field experiment
M4: Survey of vegetation in cut-over sites and production measurements
M5: Rates of photosynthesis and respiration in cut-over sites (year1) and
experiment (year 2-3)
M6: Biomass accumulation and growth biometry of keystone species in
experiment (years 2-3)
WP 02: Carbon sequestration by peatland vegetation
Deliverables:
D5: Identification of key plant species successfully occupying abandoned sites
and their potential for restoring peat accumulation
D6: Rates of carbon return from key species used in the restoration of cut-over
sites
D7: Rates of C fixation on an area basis, evaluation of carbon sequestration
through net primary production, estimation of hourly, daily and yearly net
ecosystem productivity
=> Estelle thesis on June 15th
=> Manuscript under revision in New Phytologist
WP 02: Carbon sequestration by peatland vegetation
Carbon sequestration
EEN
PPN
PG - RA - RH - FCH4
CO2
CO2
CO2
CO2
TOC
RE
CH4
Measurements
• A two year survey
• Open through flow transparent chamber (Ciras
1, PPSystems) for CO2 fluxes
• Closed darkened chambers for CH4
accumulation (micro-GC CP 4900, Varian)
• 11 collars on three vegetation types: bare peat,
recent regeneration (Eriophorum) and advanced
regeneration (Sphagnum)
• Environmental variables (air and peat
temperature, global radiation and photosynthetic
photon flux density, rainfall, water table level …)
•Biotic variables (Leaf Area Index, bryophyte
density, dessication index) => Vegetation Index
(VI) (0 to 1):

 DI  
 IF  BI * 

 DImax  

VI 
 IFmax  BImax 
Ecosystem respiration
10
RE (µmolCO2 m-2 s-1)
Bare Peat
Recent
Advanced
8
6
4
2
0
0
90
180
270
360
450
540
630
720
Days of years 2004 and 2005
Air temperature, main determinant of RE
RE (µmolCO2 m-2 s-1)
Bare peat
Recent R.
Advanced R.
 TA  Tmin   b

RE   * 
 Trèf  Tmin  
TA (°C)
Residuals of RE related to water table on bare peat
Residuals of RE (µmolCO2 m-2 s-1)
Bare Peat
WT (level of water table) (m)
WT

 
RE   a *
 c  * 
WTrèf

 
b
TA  Tmin  
Trèf  Tmin  
Residuals of RE related to vegetation index
Residuals of RE (µmolCO2 m-2 s-1)
Recent
Advanced
VI (relative unit)

  TA  Tmin   b
WT 

RE   d *
  e * VI  * 
WTrèf 

  Trèf  Tmin  
Predicted RE
RE predicted (µmolCO2 m-2 s-1)
Bare peat
Recent
Advanced
RE measured (µmolCO2 m-2 s-1)
Net ecosystem exchange under saturating irradiance
EENsat (µmolCO2 m-2 s-1)
10
Recent
Advanced
8
6
4
2
0
-2
0
90
180
270
360
450
540
630
720
Days of years 2004 and 2005
Gross photosynthesis under saturating irradiance
PBsat(µmol CO2 m-2 s-1)
14
Recent
Advanced
12
10
8
6
4
2
0
0
90
180
270
360
450
540
630
Days of years 2004 and 2005
PBsat = EENsat + RE
720
Air temperature, main determinant of PBsat
PBsat(µmol CO2 m-2 s-1)
Recent
Advanced
TA (°C)
 TA  g 


h 

PBsat   * e
2
Residuals of PBsat related to vegetation index
Residual of PBsat(µmolCO2 m-2 s-1)
Recent
Advanced
 TA  g 


h 

PBsat  f * VI * e
VI (relative unit)
2
Predicted EENsat
 TA  g 


b






WT
T
A

T
min


h
  d *

EENsat  f * VI * e 
  e * VI  * 

WTrèf 

  Trèf  Tmin  
2
EENsat predicted (µmolCO2 m-2 s-1)
Recent
Advanced
EENsat measured (µmolCO2 m-2 s-1)
Light response curves of EEN
EEN (µmolCO2 m-2 s-1)
8
6
4
2
Advanced
collar 5,
j596
0
-2
-4
-6
0
500
1000
1500
2000
PPFD (µmol/m2/s)
 i * PPFD * PBsat 
EE N  
  RE
 PBsat  i * PPFD 
Predicted EEN
EEN predicted (µmolCO2 m-2 s-1)
Récent
Advanced
EEN measured (µmolCO2 m-2 s-1)
CH4 efflux
FCH4 (nmole m-2 s-1)
70
Bare peat
Recent
Advanced
60
50
40
30
20
10
0
0
90
180
270
360
450
540
630
Days of years 2004 and 2005
720
CH4 efflux related to water table on bare peat
FCH4 (nmol m-2 s-1)
6
Bare peat
FCH4  j * WT
5
4
3
2
1
0
-0.15
-0.1
-0.05
0
WT (m )
CH4 efflux related to leaf area index of vasculars
FCH4 (nmol m-2 s-1)
Recent
Advanced
80
FCH4  k * IF
60
40
20
0
0
0.2
0.4
0.6
0.8
LAI (m2 m-2 )
1
Simulation:
Knowing:
1. Half a hour global radiation and it conversion factor to photon
flux density
2. Half a hour air and peat temperature
3. Seasonal variation of water table
4. Seasonal variation of leaf area index, bryophyte density and
moss dessication index
=> Rates of net ecosystem productivity and methane efflux can be
estimated at hourly, daily and yearly on an area basis and use to
evaluate of carbon sequestration
Daily fluxes
-2 d-1)
F
(
g
m
CO2
C
6
PB
Recent PB and RE
Recent EN
Advanced PB and RE
Advanced EN
5
4
3
2
1
0
-1
RE
-2
Bare peat EEN
-3
-4
0
90
180
270
360
450
540
630
720
Days of years 2004 and 2005
Annual carbon balance (gC m-2 y-1)
2004
PB
Bare peat
0.23
Recent
197 ~ 306
Advanced
284 ~ 474
RE
FCH4
Bilan
2005
-22
-0.4
-22
Bare peat
-121~ -207
-1.5 ~ -2.8
67 ~ 118
Recent
-186 ~ -297
-0.7 ~ -2.3
93 ~ 175
Advanced
PB
RE
FCH4
-19 ~ -31
-0.2 ~ -0.6
279 ~ 379
-199 ~ -214
-1.8 ~ -3.9
359 ~ 525
-233 ~ -340
-0.5 ~ -2.7
Bilan
-19 ~ -32
78 ~ 166
122 ~ 183
Conclusions :
1. Bare peat is a weak carbon source and vegetated areas are
strong carbon sinks
2. Net carbon exchange slightly higher for advanced than for
recent regeneration
3. High variability among collars within a given stage of
regeneration
4. Higher sensitivity to summer drought in Sphagnum covered
plots (advanced regeneration)
5. Higher methane efflux in vascular covered plots ( recent
regeneration)
Perspective : Site comparison, meta analysis …
C balance (gC m-2 y-1)
Auteurs
Country
Type
Method
Aurela et al., (2004)
Finland
Minerotrophic
Eddy flux
22
Alm et al., (1997)
Finland
Ombrotrophic
Chamber
73
Lafleur et al., (2001)
Canada
Ombrotrophic
Eddy flux
68
Lafleur et al., (2003)
Canada
Ombrotrophic
Eddy flux
71
Lafleur et al., (2003)
Canada
Ombrotrophic
Eddy flux
9
Alm et al., (1999)
Finland
Ombrotrophic,
very dry year
Chamber
-90
Waddington et al., (2002)
Quebec
Ombrotrophic,
after cutting
Chamber
-88 ~ -112
This study
Le
Russey
Bare peat
Recent
Advanced
Chambers
-19 ~ -32
67 ~ 166
93 ~ 183