recipe meeting may 17-20 th munich,germany

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

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)

I – DETERMINATION OF

VARIOUS CORRELATIONS



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 :


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

II - SUGAR ANALYSES ON BULK PEAT(comparison with fine-grained fractions)

LE RUSSEY

FRC (2nd regeneration stage)

FRD (intact area)


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 %)

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

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


Sugar analyses, preliminary conclusions

- Surface processes: evolution kinetics strongly differ in the « new » regenerating peat and in the intact peat.


III - AMINOACID ANALYSES

LA CHAUX D’ABEL

FEN SITUATIONCHA43CHA73

Aminoacid analyses, experiment


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

Chaux d’Abel, CHA situation, aminoacid results


- 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


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

?

?

?

?

? ?

=> 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 ?



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)

Frequency histograms of individual AA examplify these correlations



Good correlation between peat samplesand some living plants

Microbial production or selective preservation ?

Chaux d’Abel, sugar results on soluble fraction


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);


Higher proportions of xylose (glucose?) and fucose at depth => inheritance (xylose?) and/or in situ microbial production (fucose?)?


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:


The cryo-SEM, results, FRC 2nd regeneration stage

level 3


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


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 ?

IV – PHYSICAL MICROTEXTURE

OF THE PEAT


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)


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


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 !!!!!

recipe meeting may 17-20 th munich,germany

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