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Final Meeting. Aberdeen 28 May - 1 June. WP 6 – Carbon Turnover at different depths. Plan. Introduction Objectives and deliverables Presentation of last main results (WPI to WPIII) : Keeling plots Microbial biomass and activity Coupling microbiological and organic chemistry variables

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Final Meeting

Aberdeen

28 May - 1 June

WP 6 – Carbon Turnover at different depths


Plan

  • 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


  • Objectives
    Objectives

    • 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


    Deliverables
    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)


    Results WP I & II ….

    1 - Keeking plots

    2 - Microbial biomass

    3 - Coupling microbiological and organic chemistry variables

    4 - Peat basal respiration (CO2-CH4 profiles)


    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

    13C of respired CO2

    -28

    Advanced

    Recent

    Bare peat

    -26

    -24

    -22

    -20

    -18

    -16

    May 05

    July 05

    Aug 05

    D20 - Establishment of regeneration thresholdsOld peat vs new peat: measurements of 13C (Keeling Plots method)

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

    • 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

    • 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


    FI

    SC

    FB

    FR

    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

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

    • Kruskal-Wallis test


    Kruskal wallis test

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

    Effect of Litter plants and Water level on microbial pools

    • No effect on C microbial biomass

    • Increasing N microbial biomass under Eriophorum litter (EA : 85  1 ppm ; EV : 6310) and no difference between bare peat and Sphagnum (BP : 46  9 ppm and S : 42  9)

    • Microbial C/N lower with Eriophorum litter (EA : 4.51.0 and EV : 7.11.1) vs higher values in bare peat and Sphagnum treatment (BP : 8.6  0.9 and S : 9.4  0.9)

    Kruskal-Wallis test


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

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

    The main contributions in the co-inertia analysis were :

    biological variables (to be explained)

    Axis 1  C and N microbial biomasses and Anaerobic Activity

    Axis 2  Aerobic activity and C microbial turnover

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

    organic chemical variables (explicative)

    Axis 1  Total Organic C, Preserved Tissues, Hemicellulose and Galactose

    Axis 2  Total Organic N, Amorphous Organic matter and Decayed Tissues


    Results wp i ii 4 peat basal respiration co 2 ch 4 profiles andy

    Results WP I & II ….

    4 - Peat basal respiration (CO2-CH4 profiles)

    Andy


    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


    Microbiological indexing systems to assess peatland regeneration trends
    Microbiological indexing systems of peat accumulation processto assess peatland regeneration trends


    Disturbance of peat accumulation process

    Function (ex : C sink)

    Regeneration

    process

    Steady state

    New steady state

    A

    B

    C

    Loss of C

    Gain of C

    Time

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

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

    Disturbance, resilience, regeneration ….

    Relation between peat functional integrity, disturbance and resilience(After Herrick et Wander 1998, modified & applied to peat)

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


    Regeneration index and co 2 emission in north france peatlands

    600 of peat accumulation process

    2,0

    Drained peatlands + NPKCa

    Fertilized peatlands

    Decreasing

    « source »

    function

    (South Massif central)

    (East Massif central)

    1,5

    Index

    400

    Aerial biomass (g DM m-2)

    1,0

    Ref

    Increasing

    « source » function

    Pastured peatlands

    200

    (Somme floodplain)

    CO2 efflux (g m-2 h-1)

    0,5

    C/N sol

    Natural Sphagnum mires

    (East Massif central)

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

    0,0

    0

    1,0

    0,2

    0,4

    0,6

    0,8

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

    …. or looking for thresholds :

    0

    10

    20

    30

    40

    50

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

    - 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)

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

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

    Regeneration index and CO2 emissionin North France peatlands

    Disturbance, resilience, regeneration ….

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


    Microbial community functioning vs secondary succession

    Higher diversity of plant of peat accumulation process

    communities  high N microbial biomass

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

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

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

    Microbial community functioning vs secondary succession

    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


    C sequestration and new acrotelmic peat forming

    D20-21 - Modelling CO of peat accumulation process2-CH4-MB C potential ratios ….

    Towards other Deliverables in the research of ecological indicatorsof peat regeneration

    Signicant but R2 too low (0.1) …

    A little bit better ?

    C sequestration and new acrotelmic peat forming

    Relating organic chemistry and

    microbiological variables, not so simple :

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

    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


    Concluding remarks of peat accumulation process

    • (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


    Additionnal slides 1 results on litter wp iii ecobio 2 3 4 theoterical considerations

    Additionnal slides …. of peat accumulation process

    1 - Results on litter (WP III -Ecobio)

    2 - 3 - 4 - Theoterical considerations


    13 of peat accumulation processC - 15N Litter – Lab exp. WP III

    Litter decomposition :

    - kinetics of dry matter, C/N

    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


    Diagrammatic representation
    Diagrammatic representation of peat accumulation process

    Geology

    Hydrology

    Climat

    Biology …

    Potential

    Carbon sequestration level

    Defining factors

    Attainable

    Aeration

    Temperature

    Nutrients …

    Limiting factors

    Actual

    Drainage

    Extraction

    Erosion …

    Reducing factors

    Restoration measures

    +

    -

    0

    Peat decomposition/accumulation process : source vs sink function


    t of peat accumulation process

    t + 1

    Engineering resilience :

    Recovery time

    1)

    How quickly a system recovers from disturbance

    Evolution of the concept of resilience

    over the laste 2 decades (from Gunarson 2000 in Groffman et al. 2006)

    Ecological resilience :

    Amount of disturbance to change scale

    2)

    What amount of disturbance necessary to change the ecosystem state

    A

    B


    Criteria for ecological indicators of peat accumulation process

    (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


    Quantification of an impact andr et al 2000 modified

    Indicator of peat accumulation process

    IMPACT

    With management

    Without management

    Implantation

    Time

    Diagrammatic representation of an impact

    quantified from an environmental indicator x.

    Quantification of an impact

    (André et al. 2000, modified)


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