RECIPE meeting May 17-20 Th Munich,GERMANY
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Transcript of RECIPE meeting May 17-20 Th Munich,GERMANY
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RECIPE meeting
May 17-20Th Munich,GERMANY
« Earth Science Institute of Orleans », FranceGroup « Organic Matter in water, sols, sediments and
rocks »
Laure Comont, Fatima Laggoun-Défarge, Jean-Robert Disnar
Pascale Gautret, Nathalie Lottier, Marielle Hatton, Li Huang
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Munich progress meeting May 17-20th
WP5 work progress since Carentan meeting
II- Sugar analyses on the bulk peat compared to the fine-grained fraction(Le Russey sites on FRC & FRD) => identification of biomarkers (OM degradation processes)III- Tests of aminoacid analyses on 2 samples from CH (solid and soluble fractions) :=> interesting preliminary results obtained for identification of neoformation markers=> results are correlated with cryo-scanning electron microscopy (cryo-SEM) observations
IV – Microtexture of peat (2 distinct scales): cryo-SEM X-ray computed tomography
I – Exploration of physico-chemical data (PCA) on peat OM from the five studied sites (WP01) (correlations between C, N, organic constituent
countings; sugar analyses in both bulk peat and fine-grained fraction)
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I – DETERMINATION OF
VARIOUS CORRELATIONS
Munich progress meeting May 17-20th
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Munich progress meeting May 17-20th
Principal component analyses (PCA)
CH : 1963 (~40 yrs) and FR : 1984 (~20 yrs)FB (less than 5 yrs ?)
FI : 1975 - 1978 (~30 yrs)SC : 2000 (~5 yrs) => 1995 (~10 yrs) => 1955 (~50 yrs)
Peat harvesting ended :Peat harvesting ended :
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Munich progress meeting May 17-20th
Principal component analyses (PCA)
3 distinct trends starting from the « new » regen. peat of all sites:
- Jura sites-Scotish sites
-Finnish sites
Schematic model of peat evolution
- Similar evolution at 1st steps of regen. for Jura & Scotish sites
=> similar plant compositions of new peat (mainly Sphagna)
- Distinct evolution for FI => the composition of « litter » from Finish sites is quite different
(C.rostrata, E.vaginatum)
- The old peat evolution of SC & FI sites converge with the same variables which
characterise a more humified peat
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II - SUGAR ANALYSES ON BULK PEAT(comparison with fine-grained fractions)
LE RUSSEY
FRC (2nd regeneration stage)
FRD (intact area)
Munich progress meeting May 17-20th
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Le Russey FRC,2nd regen.stage
Sugar analyses on the BULK peat (compared to the FINE fraction <200µm)
Total sugar contents (mg/g):
- Bulk ≈ 432 (top) => 137 (bottom) - Fine ≈ 206 (top) => 80 (bottom)
sugars derived from inherited
plants tissues (Tot. Cell., Ara & Xyl)
sugars derived (partly) from microbial syntheses (Hem.Gluc, Fuc,
Rham, Man & Rib)
- High sugars decrease well correlated with %fine-grained fraction increase
- Tot.Hem.sugars increase well correlated with % of Muc.
-progressive Hem.Gluc. increase is certainly due to cellulose destructuration- High difference, between both fractions, of Rham & Rib (relative %)
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Le Russey FRD intact area
Sugar analyses on the BULK peat (compared to the FINE fraction <200µm)
Total sugar contents (mg/g):
- Bulk ≈ 295 (top) => 170 (bottom)- Fine ≈ 227 (top) => 125 (bottom)sugars derived from
inherited plants tissues (Tot. Cell., Ara &
Xyl)
sugars derived (partly) from microbial syntheses (Hem.Gluc, Fuc,
Rham, Man & Rib)
- Progressive decrease of sugars (compared to FRC) & no correlation with % fine fraction
- increase at depth corresponding to preservation processes
- Less contrast between bulk and fine peats compared to FRC
- progressive increase of H. cell. Glucose
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I-surface:
II-depth:
FRC FRD
Tot. Sugars: high degradationBulk ≈ 432 (top) => 137 (bottom) Fine ≈ 206 (top) => 80 (bottom)
Tot. Sugars: low degradationBulk ≈ 295 (top) => 170 (bottom)Fine ≈ 227 (top) => 125 (bottom)
Degradation of sugar parallelsdestructuration of plant tissues
Degradation of sugars ≠destructuration of plant
tissues Higher contribution of Rib in the fine-grained fraction
=> Degradation?
High Cellulosic sugars, Xyl in the bulk fraction
=> Primary input preservation
Munich progress meeting May 17-20th
Sugar analyses, preliminary conclusions
- Surface processes: evolution kinetics strongly differ in the « new » regenerating peat and in the intact peat.
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Munich progress meeting May 17-20th
III - AMINOACID ANALYSES
LA CHAUX D’ABEL
FEN SITUATIONCHA43CHA73
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Aminoacid analyses, experiment
Munich progress meeting May 17-20th
Acid hydrolysis HPLC quantification & distribution of AA
Living plants : Mosses: S.fallax & Polytrichum (steams & rhizoids) Cyperaceae: E.vaginatum (leaves & roots) E.angustifolium
3
4
5
6
7
8
Test of identification of total aminoacids: La Chaux d’Abel,fen situation CHA
peat profil
Soluble fraction, ultrafiltration: fraction (>3kDa) F1
fraction (<3kDa) F2
Solid bulk peat
Soluble fraction, ultrafiltration: fraction (>3kDa) F1
fraction (<3kDa) F2
Solid bulk peat
3kDa ~ 400Å
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Chaux d’Abel, CHA situation, aminoacid results
Munich progress meeting May 17-20th
- 2 compartments: soluble and solid fractions
In soluble fraction: high % of basic AA (Lys & Arg) ➱ Preferential accumulation of basic AA in acidic environment ?
➱ Another source (microorg. groups rich in basic AA)?
-Gly: smallest and simplest AA=> index of degradation
living plants
peatsoluble OM
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Munich progress meeting May 17-20th
Chaux d’Abel, CHA situation, aminoacid resultsSolid bulk
Solid fraction:All AA are well represented including
di-carboxylic AA (Asp, Glu..)
soluble (> 3kDa)
Soluble fraction:mainly composed of basic AA (Arg & Lys)+ Free ammonia => degradation markers
soluble (< 3kDa)
Example: chrommatogram of level 4 (5-10 cm)
Non proteinic AA (Orn & unknown peaks)=> neosynthetic AA from abiotic or biotic
activity
?
?
?
?
? ?
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=> 2 hypotheses - important and widespread microbial population (either active or dead) ? to be correlated with microbial groups WP03
- selective preservation of some plant proteins and accumulation due to specific environmental conditions ?
Chaux d’Abel, CHA situation, aminoacid results
Munich progress meeting May 17-20th
At 5-10 cm (regenerated peat): high diminution of total AA compared to living plants => degradation of plant proteins in this level. That’s confirmed by the total AA quantity in soluble fraction.
At 35 cm (old peat): amounts of AA are 20 times higher than those at the surface and also higher than those of living plants.
=> 20% of Gly
96% of free NH3 42% of Gly
Hydrolysable AA YIELD (mg/g) or (mg/l)
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Frequency histograms of individual AA examplify these correlations
Munich progress meeting May 17-20th
Chaux d’Abel, CHA situation, aminoacid results
Good correlation between peat samplesand some living plants
Microbial production or selective preservation ?
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Chaux d’Abel, sugar results on soluble fraction
Munich progress meeting May 17-20th
level 4 (5-10 cm) level 7 (32,5-37,5 cm)
Total sugar contents ≈ 5,5 mg/l 58% of unknowns (neoformed ?)
Total sugar contents ≈ 8,3 mg/l 23% of unknowns (neoformed ?)
Higher Total sugar contents in the soluble fraction at depth than at the sub-surface (level 7 vs. 4) are these soluble compounds autochthonous or not (i.e. brought by diffusion from the surface or elsewhere);
Microbial production or selective preservation ?
Higher proportions of xylose (glucose?) and fucose at depth => inheritance (xylose?) and/or in situ microbial production (fucose?)?
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Munich progress meeting May 17-20th
Cryo-scanning electron microscope (cryo-SEM)
The cryo-SEM is equipped with a freeze-drying sample preparation system.
It allows studing the composition and the micromorphology of hydrous materiel (peat) and spatial relationships between organic components.
FRC, 2nd regeneration stage
level 3 (0-5 cm)
level 5 (12,5 - 17,5 cm)
level 8 (42,5 - 47,5 cm)
Tests were carried out on samples from Le Russey site:
Microbial production or selective preservation ?
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The cryo-SEM, results, FRC 2nd regeneration stage
level 3
Microbial production or selective preservation ?
3D polysaccharidic networkCross section of Sphagna steam
Microorganisms inside well-preserved cell walls
level 5
BiofilmEps(extracellular polymer secretion)
level 8
3D polysaccharidic network
degraded cell walls
Bacterial colony
50µm 12µm 2,3µm
5µm 3µm 3µm
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Munich progress meeting May 17-20th
Preliminary conclusions
distinct degradation processes between these 2 peat samples:
Solid fraction Soluble fraction
Total AA ≈ 5 µg/mg Total AA ≈ 43,51µg/ml
Total sugars ≈ 5.5 mg/l
level 4 : - High living plant proteinsdegradation in the solid fraction
- High sugars degradation in soluble fraction
Solid fraction Soluble fraction
Total AA ≈ 13,14 µg/ml
Total sugars ≈ 8,3 mg/l
Total AA ≈ 134 µg/mg
level 7 : - High hydrolysable AA yield
in the solid fraction ≠ materiel sources lower degradation
- Higher Tot. sugar contents in the soluble fraction
2 processes are determined : - Selective preservation - Microbial production
Which of these 2 processes is dominant ?
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IV – PHYSICAL MICROTEXTURE
OF THE PEAT
Munich progress meeting May 17-20th
FRA, bare peat
level 3 (0-5 cm)
FRC, 2nd regeneration stage
level 3 (0-5 cm)
level 5 (12,5 - 17,5 cm)
level 8 (42,5 - 47,5 cm)
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Munich progress meeting May 17-20th
Physical microtexture of the peat
I- Cryo-SEM observations:
bare peat, FRA 2nd reg. stage, FRC
more compact, dense peat
analyses are in progress
distinct µmorphologies in the bare peat & the transition « old »/« new » peat
II- X-ray computed Tomography :
Tests carried out on 2 samples (Coll. R. Swennen from Leuven University, Belgium):RyI = FRC level 7-12 cm RyI = FRC level 40-50 cm
Visualisation of the 3D porous network on different peattypes under increasing range of wetness (re-wetting process)
level 3 level 5
5µm 5µm
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Munich progress meeting May 17-20th
Conclusions
- Association of AA analyses + sugar analyses in soluble fraction
=> interesting approach to better identify the markers of OM degradation
to be applied in WPO2…- Exploration of physico-chemical data (PCA) on peat OM from the five sites (WP01)
=> distinct evolution trends for Jura peatlands and SC/FI peatlands => climatic influence ? Initial
vegetation types ?
-2 important problems arise:
=> datations of both «new» peat horizons and transitional peat layer
=> insufficient numbers of peat samples along the profiles of the new regenerating horizon (only 2 to 3)
For WPO2 => adopt a better strategy of sampling !!!!!