WP O6 - Carbon turnover Final Meeting

ECOBIO

UMR 6553

Aberdeen28 May - 1 June

WP 6 – Carbon Turnover at different depths

WP O6 - Carbon turnover

• Introduction • Objectives and deliverables

• Presentation of last main results (WPI to WPIII) :• Keeling plots

• Microbial biomass and activity

• Coupling microbiological and organic chemistry variables

• Peat basal respiration (CO2-CH4 profiles)

• Microbiological indexing systems• Considering the microbioligical variables as indicators • Disturbance, resilience, regeneration …• Microbial community functioning vs secondary succession

• Concluding remarks

Plan

WP O6 - Carbon turnover

– To determine the impact of recolonizing vegetation (Sphagnacae, vascular plants) on soluble organic forms of C and N and emissions of CO2 and CH4 from restored cut-over sites

– To correlate rates of C turnover with structure of microbial communities (WP03) and the peat organic matter components at different depths (WP05)

– To relate C turnover to management practices and procedures at different time scales

Objectives

WP O6 - Carbon turnover Deliverables

– D 19 – Production of isotopically labelled 13C/15N• WP III : lab and field experiment

– D20 - Establishment of regeneration thresholds in terms of « link-source » and assessment of the origin of C in gaseous efflux

• WP I : field experiment• Connexion with D6, D7 (WP02), D23 (WP 07)

– Keeling plots (Daniel E. presented by AJ + )

– D21 - Modelling CO2-CH4-Microbial biomass C potential ratios in different cases of peatland restoration including the influence of N-litter

• WP I + WP II + WP III• Connexion with D16 (see Fatima report on WP5)

– Effect of plant species on microbial biomass (AJ)– Modelling microbiological indicators (AJ)– CO2/CH4 peat profiles (Andy)

WP O6 - Carbon turnover

Results WP I & II ….

1 - Keeking plots2 - Microbial biomass

3 - Coupling microbiological and organic chemistry variables

4 - Peat basal respiration (CO2-CH4 profiles)

WP O6 - Carbon turnover

D20 - Establishment of regeneration thresholds Old peat vs new peat: measurements of 13C (Keeling Plots

method)

• The isotopic signature of respired CO2 ranged between -19.5 and -26.5 ‰ and it varied among plots and seasons

• Bare peat respired more 13C enriched CO2 than revegetated plots

-28

-26

-24

-22

-20

-18

-16

May 05 July 05 Aug 05

Advanced Recent Bare peat

13C of respired CO2

13C of bulk organic

matter (‰)

Mosses -28.16 0.05

Vascular plants -26.50 0.44

Peat cores :  

advanced regeneration -27.31 0.19

recent regeneration -26.21 0.12

bare peat -25.98 0.12

• This is consistent with the isotopic signatures of bulk organic matter of peat and vegetation

• Respired CO2 is enriched in 13C when compared with bulk organic matter, suggesting negative fractionation during respiration

• Objective : determination of the contribution of new peat and old peat to CO2 emission

WP O6 - Carbon turnover

D21 - Modelling CO2-CH4-Microbial biomass C potential ratios

Effect of Living plants and Water level on microbial pools

• No significant effect of plant and water level on soluble C-N-C/N

Nitrogen microbial biomass

0

50

100

150

200

250

300

350

High Medium Low

0

50

100

150

200

250

300

350

High Medium Low

0

50

100

150

200

250

300

350

High Medium Low

Microbial C/N

0

5

10

15

20

25

High Medium Low

Aitoneva (FI)

0

5

10

15

20

25

High Medium Low

Middlemuir (UK)

0

5

10

15

20

25

High Medium Low

Baupte (F)

•Kruskal-Wallis test

Effect

PLANT

P value

WATER LEVEL

P value

N - MB

Yes

0.004

No

0.191

C/N

No

0.784

No

0.606

C - MB

Yes

0.009

No

0.795

Carbon microbial biomass

0

200

400

600

800

1000

1200

1400

1600

High Medium Low

Bare peat

Sphagnum

E. vaginatum

E. angustifolium

0

200

400

600

800

1000

1200

1400

1600

High Medium Low

0

200

400

600

800

1000

1200

1400

1600

High Medium Low

FI

SC

FB

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

High Medium Low

Water level

0

500

1000

1500

2000

2500

3000

3500

High Medium Low

Water level

0

5

10

15

20

25

High Medium Low

Water level

Bare peatSphagnumE. vaginatumE. angustifolium Russey (F)

FR

• Only a significant effect of plant on C and N microbial biomasss

WP O6 - Carbon turnover

Kruskal-Wallis test

Nitrogen microbial biomass in the trenches Surface (0-10 cm)

0

20

40

60

80

100

120

140

160

180

200

Bare peat Sphagnum E. vag. E. angustif.

N-M

B (

µg

N g

Dry

Pea

t-1

)

Nitrogen microbial biomass in the trenches Depth 7 (32.5-37.5 cm)

0

20

40

60

80

100

120

140

160

180

200

Bare peat Sphagnum E. vag. E. angustif.

WT 1

WT 2

WT 3

Effect

LITTER

P value

WATER LEVEL

P value

• Increasing N microbial biomass under Eriophorum litter (EA : 85 1 ppm ; EV :

6310) and no difference between bare peat and Sphagnum (BP : 46 9 ppm and S : 42 9)

N - MB

Yes

0.022

No

0.372

C/N

Yes

< 0.001

No

0.197

Carbon microbial biomass in the trenches Surface (0-10 cm)

0

100

200

300

400

500

600

700

800

900

Bare peat Sphagnum E. vag. E. angustif.

C-M

B (

µgC

gD

ry P

eat

-1)

Carbon microbial biomass in the trenches Depth 7 (32.5-37.5 cm)

0

100

200

300

400

500

600

700

800

900

Bare peat Sphagnum E. vag. E. angustif.

WT 1

WT 2

WT 3

• No effect on C microbial biomass

• Microbial C/N lower with Eriophorum litter (EA : 4.51.0 and EV : 7.11.1) vs higher values in bare peat and Sphagnum treatment (BP : 8.6 0.9 and S : 9.4 0.9)

C - MB

No

0.836

No

0.635

D21 - Modelling CO2-CH4-Microbial biomass C potential ratios

Effect of Litter plants and Water level on microbial pools

WP O6 - Carbon turnover

Coupling microbial variables –organic chemistrymultivariate analyses using constrained ordination methods (Co-

inertia)

CHSfEa54

CHSfEa56

CHSfEa58

CHSPse253CHSPse254

CHSPse256

CHSPse258

CHSfEv503

CHSfEv504

CHSfEv506

CHSfEv508

FRBare53

FRBare54

FRBare56

FRSfEa54

FRSEEC504

FRSEEC506

FBBare53

FBBare54

FBEa53FBEa54

FBEa58

FIEvw106

FIEvd103

FIEvd104

FIEvd106

FICr103

FICr104

FICr106

FICr108

FISf106

SCBare13

SCBare14

SCSf54

SCSf56

SCEa53SCEa54

SCSpMo503

SCSpMo504

SCSpMo506

-2.9

1.9-3.2 1.8

Cmicroppm

Nmicroppm

CsNmicro

CmicromgL

NmicromgL

AerAct

AnaerAct

AeActmass

AnaActmass

AeAnaRatio

CminRateAe

CminRateAn

MicTuOvAe

MicTuOvAna

-0.49

0.21-0.38 0.26

Biological Variables in the Co-inertia plan 1 (All sites)

COTpc

NOTpc MOARpc

PresTIpc

DegTIpc

MUCILpc

FinFRApc

GlucHpc

HemiTpm

CelluloTpm

BulkDgL

SOCppm

SONppm

soluCsN

ArabinpcRhamnpc

RibpcFucpc

MannpcGalactpc

Xylpc

-0.28

0.47-0.39 0.36

Chemical Variables in the Co-inertia Plan 2 (All sites)

organic chemical variables (explicative)Axis 1 Total Organic C, Preserved Tissues, Hemicellulose and GalactoseAxis 2 Total Organic N, Amorphous Organic matter and Decayed Tissues

biological variables (to be explained)Axis 1 C and N microbial biomasses and Anaerobic ActivityAxis 2 Aerobic activity and C microbial turnover

The main contributions in the co-inertia analysis were :

WP O6 - Carbon turnover

Results WP I & II ….

4 - Peat basal respiration (CO2-CH4 profiles)

Andy

WP O6 - Carbon turnover

Microbiological indexing systems for assessing regeneration of peat accumulation process

1 - Considering the microbioligical variables as indicators

2 - Disturbance, resilience, regeneration …3 - Microbial community functioning vs secondary

succession

WP O6 - Carbon turnover

Microbiological indexing systemsto assess peatland regeneration trends

C mineralization rate = microbial quotient

= in relation with organic matter quality= allows to compare rates of activity in peat with different organic C status

- sensitive to land management i.e. increase with peat extraction no early change after restoration management

Microbial variables Characteristics (Relationship to peat function, causes of variations

Responses (processes in the upper part of peat profile (0- 50 cm max)

Microbial Biomass C, N, C/N

= labile pool vs sink= driving force to nutrient transformation= aggregative agent

- Sensitive to restoration management i.e. increasing of C-N microbial stocks- sensitive to peat extraction (declining with aeration, erosion and subsidence)

Basal Respiration anaerobic & anaerobic

= activity of the microbial pool and capacity of mineralisation= flux of C (source)

- change with peat age and regeneration stages (low in early secondary succesion)- high in natural peatland vs low in cutover peatland

Microbial turnover rate = Microbial metabolic Qqtient

Changes in MTR (=MMQ) = change in substrates or= change in microbial community or= change in substrate and community or= change in the physiological status of communities due to altered requirement

- no difference between disturbed situation and natural- less sensitive to regenertation gradient

WP O6 - Carbon turnover

Relation between peat functional integrity, disturbance and resilience

(After Herrick et Wander 1998, modified & applied to peat)

C

Function (ex : C sink)

Time

B

New steady state

Disturbance

A

Steady state

Loss of C

Regeneration

process

Gain of C

N microbial biomass

y = -0.53x2 + 36.82x - 120.93R2 = 0.833

0

200

400

600

0 10 20 30 40 50

Age of regeneration (years)

µg

N g

Dry

Pea

t -1

C microbial biomass

y = -3.20x2 + 216.15x - 666.22R2 = 0.819

0

1000

2000

3000

0 10 20 30 40 50

µgC

gD

ry P

eat -1

Modelling the C-N microbial biomass vs age of regeneration (WP I results)

D20-21 - Modelling CO2-CH4-MB potential ratios :

Towards other Deliverables in the research of ecological indicators of peat regeneration ….

Disturbance, resilience, regeneration ….

WP O6 - Carbon turnover

0

200

400

600

0 10 20 30 40 50

C/N sol

Aeri

al bio

mass

(g D

M m

-2)

Regeneration index and CO2 emission

in North France peatlandsIndex

0,0

0,5

1,0

1,5

2,0

0,2 0,4 0,6 0,8 1,0

CO2 efflux (g m-2 h-1)

D20-21 - Modelling CO2-CH4-MB potential ratios :

Towards other Deliverables in the research of ecological indicators of peat regeneration ….

Pastured peatlands

(Somme floodplain)

Fertilized peatlands(East Massif central)

Natural Sphagnum mires

(East Massif central)

Drained peatlands + NPKCa(South Massif central)

Index = 0,19 (CO2)-2,42 (R2 = 0,92)

Biomass = 10713 (C/N)-1,18 ; R2 = 0,52

Relation aerial vegetal biomass vs C/N soil ratio in French peatlands

Disturbance, resilience, regeneration ….

- left graph different stages (--) of recovering process by refering (Ref) to a known «natural ecosystem» ;

Ref

…. or looking for thresholds :

Increasing« source » function

Decreasing « source » function

- right graph step by step way to define the « O » level beyond we recover the function (+ values of index) or not (- values) ( ex : C sink-source function in peatlands)

WP O6 - Carbon turnover

y = 0.536x-0.578

R2 = 0.470

0.0

0.2

0.4

0.6

0.8

0 20 40 60 80 100

Aerobiosis

MM

Q d

ay-1

Microbial community functioning vs secondary succession

y = 0.268x-0.493

R2 = 0.525

0.0

0.2

0.4

0.6

0.8

0 20 40 60 80 100

Nitrogen Microbial Biomass (mg N L-1)

Anaerobiosis

MM

Q d

ay-1

High dominance of one species in the plant communities low N microbial biomass

Higher diversity of plantcommunities high N microbial biomass

Earlier stages of secondary succession on bare peat 1-10 years after abandonment of extraction

Older stages of secondary succession on bare peat 10-50 years after abandonment of extraction

D20-21 - Modelling CO2-CH4-MB potential ratios :

Towards other Deliverables in the research of ecological indicators of peat regeneration ….

WP O6 - Carbon turnover

Signicant but R2 too low (0.1) …

Aerobic Microbial Activity vs C/N peat

0

5

10

15

20

0 20 40 60Peat C/N

µg

C g

DP

-1

A little bit better ?

y = -1.35Ln(x) + 7.37R2 = 0.151

02468

10121416

0 10 20 30 40 50 60

Preserved Tissus(%)

µg C

g D

P -1

Anaerobic Activity vs Preserved Tissus in peat

Relating organic chemistry andmicrobiological variables, not so simple :

2) A new horizon : applying the Clymo ’s model to acrotelm regeneration

C sequestration and new acrotelmic peat forming

0

500

1000

0 1 2 3 4 5

Time (years)

Sphagnum fallax :

P = 420 g m-2 yr-1, a = 0.30 yr-1

Pradeaux peatland (63)

Eriophorum angustifolium :

P = 220 g m-2 yr-1, a = 0.72 yr-1

Baupte peatland (50)A

ccu

mu

late

d p

eat

(g D

M m

-2 )

Considering pa = input of dry matter in the peat, a the decomposition rate :

dx/dt = pa - a x with the following solution :

x pa /a (1 - e- at) = accumulated peat

D20-21 - Modelling CO2-CH4-MB C potential ratios ….

Towards other Deliverables in the research of ecological indicatorsof peat regeneration

WP O6 - Carbon turnover

Concluding remarks• (1) Microbiological variables and ratios :

– Microbial biomass C or N : signifcant responses with plant community and regeneration age ;

– Ratios such as Carbon Turnover also show along the gradient of regeneration stages

– CH4/CO2 ratios (potential activity) : not enough sensitive as a regeneration index in our experiment

• (2) Modelling kinetics– CO2 kinetics in laboratory (potential activity) : classical fitness to a simple

model (one compartment in most of kineticss, sometimes two)

• (3) Need to be completed :– Use of Clymo’s model of accumulation with results of production and

decomposition in Le Russey (WP III)– Further investigation in coupling organic chemistry and blobal microbial

variables (will be done in July)

– Relationships between kinetics of CO2-CH4 in lab with structure of microbial communities

WP O6 - Carbon turnover

Additionnal slides ….

1 - Results on litter (WP III -Ecobio)2 - 3 - 4 - Theoterical considerations

WP O6 - Carbon turnover

13C - 15N Litter – Lab exp. WP III

Litter decomposition :

- kinetics of dry matter, C/N

Kinetics of litter decomposition

0

20

40

60

80

100

0 20 40 60 80 100 120 140 160 180 200

Time (days from start T0)

Sphagnum

E. angustifolium

E. vaginatum

C/N ratio fluctuations

0

10

20

30

40

50

60

0 20 40 60 80 100 120 140 160 180 200

Time (days from start T0)

Sphagnum

E. angustifolium

E. vaginatum

Kinetics of delta 13C

-20

0

20

40

60

80

0 50 100 150 200

Time (days from start T0)

Sphagnum

E. angustifolium

E. vaginatum

Kinetics of delta 15N

0

10000

20000

30000

40000

50000

0 50 100 150 200

Time (days from start T0)

delta

°/°

°Sphagnum

E. angustifolium

E. vaginatum

C - mircrobial biomass : surface peat layer

0

200

400

600

800

1000

1200

1400

1 15 60 180

µg C

DP

-1

TN A SPH A E ANG A E VAG A

N - microbial biomass : surface peat layer

0

50

100

150

200

250

1 15 60 180

Incubation time (days)

µg N

DP

-1

TN A

SPH A

E ANG A

E VAG A

Microbial biomass in the peat columns : - calculation of 15N and 13 C recovery in progress - labeled 15N found in unfumigated and fumigated extract, in N mineral extract too

- 13C-15N deltas

WP O6 - Carbon turnover

Diagrammatic representation

+-Peat decomposition/accumulation process : source vs sink function

0

GeologyHydrologyClimatBiology …

AerationTemperatureNutrients …

Attainable

DrainageExtractionErosion …

PotentialDefining factors

Limiting factors

Carb

on

seq

uest

rati

on

le

vel

Actual

Restoration measures

Reducing factors

WP O6 - Carbon turnover Evolution of the concept of resilienceover the laste 2 decades (from Gunarson 2000 in Groffman et al. 2006)

t t + 1

A B

Engineering resilience :Recovery time

Ecological resilience :Amount of disturbance to change scale

1) How quickly a system recovers from disturbance

2) What amount of disturbance necessary to change the ecosystem state

WP O6 - Carbon turnover

Criteria for ecological indicators(after Dale & Beyeler (2001)

•are easily measured

•are sensitive to stress on system

•respond to stress in a predictable manner

•are anticipatory : signify an impending change in the ecological system

•predict changes that can be averted by management actions

•are integrative : the full suite of indicators provides a measure of coverage of the key gradients across the ecological systems (e.g. soils, vegetatyion types, temperature, etc.)

•have a known response to natural disturbances, anthropogenic stresses, and change over time

•have low variability in response

WP O6 - Carbon turnover

Diagrammatic representation of an impactquantified from an environmental indicator x.

Quantification of an impact(André et al. 2000, modified)

Indicator

Time

Without management

With management

Implantation

IMPACT