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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 cut-over 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
CO2
CH4CH4
PG - RA
CO2
CO2
RE
CO2CO2
Carbon sequestration
PPN
EEN
TOC
- RH - FCH4
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):
BImaxIFmax
DImaxDI
*BIIF
VI
Ecosystem respiration
0
2
4
6
8
10
0 90 180 270 360 450 540 630 720
Bare PeatRecentAdvanced
Days of years 2004 and 2005
RE (µmolCO2 m-2 s-1)
Air temperature, main determinant of RE
b
minrèf
minAE
TT
TT*R
TA (°C)
Bare peatRecent R.
Advanced R.
RE (µmolCO2 m-2 s-1)
Residuals of RE related to water table on bare peat
b
TT
TT*c
WT
WT*aR
minrèf
minA
rèfE
Bare Peat
WT (level of water table) (m)
Residuals of RE (µmolCO2 m-2 s-1)
Residuals of RE related to vegetation index
bed
minrèf
minA
rèfE
TT
TT*VI*
WT
WT*R
Residuals of RE (µmolCO2 m-2 s-1)
RecentAdvanced
VI (relative unit)
Predicted RE
RE predicted (µmolCO2 m-2 s-1)
Bare peatRecentAdvanced
RE measured (µmolCO2 m-2 s-1)
Net ecosystem exchange under saturating irradiance
-2
0
2
4
6
8
10
0 90 180 270 360 450 540 630 720Days of years 2004 and 2005
EENsat (µmolCO2 m-2 s-1)
RecentAdvanced
Gross photosynthesis under saturating irradiance
0
2
4
6
8
10
12
14
0 90 180 270 360 450 540 630 720
PBsat(µmol CO2 m-2 s-1)
RecentAdvanced
Days of years 2004 and 2005
PBsat = EENsat + RE
Air temperature, main determinant of PBsat
h
gA
Bsat
T
e*P
2
TA (°C)
PBsat(µmol CO2 m-2 s-1)
RecentAdvanced
Residuals of PBsat related to vegetation index
h
g
f
A
Bsat
T
e*VI*P
2
VI (relative unit)
RecentAdvanced
Residual of PBsat(µmolCO2 m-2 s-1)
Predicted EENsat
bedh
g
f
minrèf
minA
rèf
A
NsatTT
TT*VI*
WT
WT*
T
e*VI*EE
2
RecentAdvanced
EENsat measured (µmolCO2 m-2 s-1)
EENsat predicted (µmolCO2 m-2 s-1)
Light response curves of EEN
-6
-4
-2
0
2
4
6
8
0 500 1000 1500 2000
PPFD (µmol/m2/s)
EEN (µmolCO2 m-2 s-1)
Advanced collar 5,
j596
EBsat
BsatN R
PPFD*P
P*PPFD*EE
i
i
Predicted EEN
EEN predicted (µmolCO2 m-2 s-1)
EEN measured (µmolCO2 m-2 s-1)
RécentAdvanced
CH4 efflux
0
10
20
30
40
50
60
70
0 90 180 270 360 450 540 630 720Days of years 2004 and 2005
Bare peatRecent Advanced
FCH4 (nmole m-2 s-1)
CH4 efflux related to water table on bare peat
0
1
2
3
4
5
6
-0.15 -0.1 -0.05 0
FCH4 (nmol m-2 s-1)
WT (m )
Bare peat
WT*F 4CH j
CH4 efflux related to leaf area index of vasculars
0
20
40
60
80
0 0.2 0.4 0.6 0.8 1
FCH4 (nmol m-2 s-1)
LAI (m2 m-2 )
RecentAdvanced
IF*F 4CH k
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
-4
-3
-2
-1
0
1
2
3
4
5
6
0 90 180 270 360 450 540 630 720
FCO2 ( gC m-2 d-1)
Days of years 2004 and 2005
PB
RE
Advanced PB and RE
Advanced EN
Bare peat EEN
Recent PB and RE
Recent EN
Annual carbon balance (gC m-2 y-1)
2004 Bare peat Recent Advanced
PB 0.23 197 ~ 306 284 ~ 474
RE -22 -121~ -207 -186 ~ -297
FCH4 -0.4 -1.5 ~ -2.8 -0.7 ~ -2.3
Bilan -22 67 ~ 118 93 ~ 175
2005 Bare peat Recent Advanced
PB 279 ~ 379 359 ~ 525
RE -19 ~ -31 -199 ~ -214 -233 ~ -340
FCH4 -0.2 ~ -0.6 -1.8 ~ -3.9 -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 …
Auteurs Country Type Method C balance (gC m-2 y-1)
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
