Diapositive 1

1
WP05 physico-chemical quality of peat OM
RECIPE meeting May 29th-31th Aberdeen, Scotland
D 18 Physico-Chemical characterisation of the
Organic Matter (OM) - ISTO
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WP05 physico-chemical quality of peat OM
RECIPE meeting May 29th-31th Aberdeen, Scotland
D 18 - WP1
1 Bulk indicator micromorphology (bulk peat)
2 Bulk indicator C/N (bulk peat and
fine-grained fraction)
3 Molecular indicator sugars (bulk peat and
fine-grained fraction)
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1. Bulk indicator Microremain counts
New regenerating peat
All sites pooled
AOM
AOM
AOM
Muc
Muc
Muc
Pol.
Sp.
Sp.
Sp.
Sp.
Er.
Pol.
Er.
1) Heterogeneous inherited tissues tend to become
more homogeneous (dominance of Sphagna) 2)
Increase of percentages of humified materials and
microbial secretions.
AOM
Old peat
Composed of - microbial secretions -
humified materials - structureless tissues
Muc
4
1. CryoSEM Texture of Le Russey bulk peat
Evolution of the bare peat surface along a
trend of regeneration
Eriophorum species
Bare peat
FRA
FRB

• Bare peat gt Impact of the exploitation

5µm
5µm
New peat (25years)
Intact
FRC
FRD
- Texture at 25yrs intact
Higher biodegradation in early regenerating
stages than in the advanced ones
5µm
5µm
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1. CryoSEM Microorganisms (Le Russey)
SURFACE
SURFACE
SURFACE
12µm
3.75µm
10µm

• At surface peat gt high diversity, high abundance

Same diversity in November 2001, 2003 and June
2005
DEPTH
DEPTH
3µm
- At depth gt low diversity (bacteria), low
abundance
2µm
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2. Bulk indicator atomic C/N bulk
3 2.5 cm 4 7.5 cm
6 25 cm 8 45 cm
5-10 years
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3. Molecular indicators Total sugars
3 2.5 cm 4 7.5 cm
6 25 cm 8 45 cm
Fine-grained fraction lt 200 µm (strong hydrolysis)
Intact and gt 50 years
5-10 years
25-45 years
mg/g
mg/g
mg/g
High total sugar content, except for FB No
difference between recent and advanced
regeneration stages Recent regenerating stage gt
TS ? 200mg/g In advanced stage gt TS ? 200 mg/g
but within a profile total sugar content can
reflect the difference between  new  and
 old  peat
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WP 1 Recording of source materials in a
regeneration trend (mg g-1) at the Scottish
site 63 µm lt fraction lt 200 µm (weak hydrolysis)
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Bare peat 5 years
WP 1 Evolution of microremains during
regeneration at the Scottish site
Eriophorum 10 years
Dominance of AOM and unspecified tissues
2.5 cm
Sphagnum 10 years
7.5 cm
Mixed vegetation 50 years
25 cm
45 cm
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WP 1 Influence of the water table on sugar
content () in wet and dry Eriophorum situations
in Finland (weak hydrolysis) 63 µm lt fraction lt
200 µm
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WP 1 Influence of time on sugar content () in
Sphagnum fallax situations in Scotland (weak
hydrolysis) 63 µm lt fraction lt 200 µm
Compared to Eriophorum, sugar content of peat
tend to be similar to the composition of the
source material
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Work Program 1 D 18 Physico-chemical
characteristics of peat differences between
 old  and  new  peat

• gt The old humified peat shows distinctive
  properties characteristic of an intensive
  degradation of OM, such as
• Large amounts of amorphous OM and mucilage.
• High compaction (bulk density gt 0.15g.m-3),
• Lower C/N ratios (20-30).

• gt Indicators of the new regenerating peat show
• Microremains dominated by preserved tissues,
  especially from Sphagnum
• Low compaction (bulk density lt 0.05g .m-3)
• Higher C/N ratios (30-45)

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Work Program 1 D 18 Physico-chemical
characteristics of peat dynamics of OM quality

• Microremain counts in new peat showed
• 1) deacrasing relative amount of preserved
  tissues, with more homogeneous peat in advanced
  stages (Sphagnum less degraded than Eriophorum)
• 2) increasing relative amount of humified
  materials

• Molecular analysis showed
• 1) vegetation contribution to chemical
  composition of OM during regeneration
• 2) effect of rewetting on OM chemistry (less
  source markers, more hemi G in dry conditions)

• Similar 1st steps of regen. for Jura Scotish
  sites
• gt similar plant compositions of new peat
  (mainly Sphagna)

• Distinct evolution for F
• gt  litter  composition in Finish sites is
  quite different (C.ros, E.vag)

- The old peat evolution of SC FI sites
converge with the same variables which
characterise a more humified peat
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WP05 physico-chemical quality of peat OM
RECIPE meeting May 29th-31th Aberdeen, Scotland
D 18 WP2
CNS results
Sugars analysis results
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1. Bulk indicator site effect on C/N
Chemical characterisation of the peat from each
site
Baupte Lower C, higher N and S
Finland Lower C, intermediate N and S
Scotland higher C, intermediate N and S
Le Russey higher C, lower N and S
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1. Bulk indicator C/N depth effect
Tend to increase with depth
Tend to decrease with depth
Higher N content at the surface
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1. Bulk indicator water table (WT) and
vegetation (Veg) effect
Kruskal Wallis testing main effects
- In all sites Veg had no significant effect on
N, but
Baupte
Le Russey
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1. Bulk indicator
Bulk analyses were able to - show site and depth
effect on C/N - record effect of water table and
vegetation on C in spite of the short period of
study
Response of C and N content to water table and
vegetation seems to depend on peat type (site
characteristics) and history of exploitation
Finland
Le Russey
Baupte
Scotland
Increase of sensitivity to treatments
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2. Sugar analysis FI low water table 12.5 cm
Hot water extraction versus weak hydrolysis
extract the most labile sugars newly synthesized



Hot water extraction
Weak hydrolysis
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2. Sugar analysis problem encountered
November 2005
IS
IS
G
R
XF
G
A
M
Ga
March 2006
IS
IS
Hot water extractable sugars are very sensitive
to storage condition
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2. Sugar analysis vegetation effect on glucose
(µg g-1)
In other sites than Baupte, Eriophorum situation
tend to contain more hot water extractable glucose
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2. Sugar analysis water table effect on glucose
(µg g-1)
In other sites than Baupte, water table tend to
affect hot water extractable glucose
23
2. Sugar analysis depth effect on glucose
(µg g-1)
Trend of hot water extractable glucose with
depth tend to be different between site
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2. Sugar analysis synthesis
Results difficult to interpret because
- difficult to know if the glucose was from plant
or microbial origin

• difficult to know how much is consumed versus how
  much is produced very sensitive marker

• methodological difficulties (storage)

• time of experiment may be too short to produce
  significant differences on the peat chemistry

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2. Sugar analysis synthesis
HOWEVER
- hot water extraction revealed to be a good
method to detect sugars from microbial or plant
exudates origin compared to weak hydrolysis (on
bulk material or size fractions)

• similarities / differences between sites
• Scotland / Le Russey
• Finland
• Baupte

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WP 1 and WP 2 General synthesis
Age effect Microremain counts In the first
stages, vegetation dominated by Eriophorum (FR,
FI) BUT heterogeneous underlying new peat. In
advanced regenerated stages, mixed vegetation BUT
homogeneous underlying new peat (derived Sphagnum
tissues).
Difference of decomposition rate between plants
remains is highlighted by microremain counts

• This is confirmed
• at Le Russey, by Cryo SEM with the observation of
  more degraded tissues in early than advanced
  stages at the same depth (WP1),
• at the Finnish site, with sugars analysis gt
  higher preservation of Sphagnum than Eriophorum
  (WP1),
• N tend to be higher under Eriophorum in FR, FI
  and SC at the surface gt potential higher
  microbial activity (WP2).

• Change of chemical composition with regeneration
• In SC (WP1), sugar analyses were able to show
  changes of peat chemical characteristics induced
  by plant inputs. Depending on the history of
  exploitation and bare peat composition,
  revegetalisation may affect peat chemical
  composition
• at a different rate (different sensitivity to
  changes of water table and vegetation, WP2)
• in a different manner? (different impact of a
  same vegetation depending on site, WP2)

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Site effect Results of both WP1 and WP2
separated Baupte from the other sites (lower C/N
and total sugar content), clearly separating this
site in terms of the degree of decomposition of
their peat WP1 results on old peat grouped SC and
FI sites with higher C/N than the Jura sites.
This difference tend to disappear in regenerated
peat (cf Jura sites and SC). The similarity in
the first regeneration stages regeneration tend
to be confirmed by the sugar analysis of the WP2,
where the peat of Le Russey and Scotland seem to
respond in a similar way to treatments
Depth effect -WP1 C/N, sugars and
micromorphology differenciation of new/old peat.
Micromorphology and sugars analyses brought more
detailed information on the quality of the
regenerating peat than C/N
Water table effect -WP1 in wet conditions,
better preservation of OM under a same vegetation
(sugar distribution in FI). This is confirmed by
the higher C content.
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Involvement of OM characterisation in the process
of exploited site rehabilitation
As bulk analyses such as C/N do not provide
detailed informaton on peat quality
As sugar content maybe too expensive to implement
29
And many thanks to those who participated to
RECIPE at ISTO Laure Comont, Christian Défarge,
Jean-Robert Disnar, Pascale Gautret, Sébastien
Gogo, Marielle Hatton, Fatima Laggoun, Nathalie
Lottier and Amélie Fleury (1 year) Also student
trainees Li Huang, Joséphine Vicelli
30
Problems encountered in the interpretation of OM
data
WP 1 Too low number of samples in regenerated
peat (sample 3 missing in some cases) Lack of
reference situation in Baupte, Finland and
Scotland Reference situations of Jura sites were
not studied by all partners of the consortium

• WP 2
• Short time of experiment many factors
  interacting
• Difficult to highlight differences in the peat
  chemistry
• Peat substrate reactivity lack of control that
  could separate input from plants and reaction of
  these inputs with the microbial community
  (sterilised substrate used as control)

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1. Micromorphology OM diagenesis
An example of le Russey site transverse section
of Sphagna stems in below litter compartment
0-5 yrs Eriophorum
25 yrs Mixed vegatation
Intact
FRB
FRC
FRD
Thick well-preserved cell walls with filled
cavities
Intermediate degradation stage
fine cell walls with empty cavities
more rapid peat degradation in the first
regenerating stage than in the advanced stage
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2. Bulk indicator C/N Bulk/Fine fraction
5-10 years
50 years
Jura
Scotland
Jura (Intact)
Scotland
Finland
Finland
Baupte
No differences of the C/N ratio between these
both fractions
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2. Bulk indicator C/N diverse fractions
5-10 years
50 years
Finland
Finland
Significance differences in
Scotland
Scotland
34
3. Molecular indicators Total sugars
An example of le Russey, comparaison of sugars in
bulk peat and in the fine-grained fraction lt200µm
Intact gt 50 years
25 years




35
WP 1 Evolution of peat granulomtry during
regeneration (mg g-1) at the Scottish site
Increase amount of coarse-grained fraction when
both plants (mixed vegetation) are allowed to
interact for a long time
36
WP 1 Influence of the water table on sugar
content (mg g-1) in wet and dry Eriophorum
situations in Finland 63 µm lt fraction lt 200 µm
1) Sugars markers of vascular plants are consumed
in dry situation, whereas they tend to be
conserved in wet environment

• 2) Microbial markers
• Fucose more abundant in wet situation than in dry
  situation
• Rhamnose, mannose and glucose more abundant in
  dry situation

Analysis of sugars are able to track changes in
microbial communities structure and activity??
37
WP 1 Influence of the water table on the peat
granulometry in wet and dry Eriophorum situations
in Finland
Coarse grained fraction is found in higher
amounts in wet conditions than in dry conditions
Water table affect the peat granulometry
reflecting degradation processes
38
WP 1 Influence of the water table on the
macrorests
Global similar macrorest profile between the two
situation
Eriophorum wet
Eriophorum dry
Poor indicator of water table effect
39
ISTO in the WP2

• Chemical characterisation of the peat from the
  different situations with different approaches
• Aim determine the effects of site, vegetation,
  water table and depth on chemical properties of
  peat
• Integration with other results definition of
  indicators of carbon sequestration

40
ISTO in the WP2
Level of analysis Analysis (method) Samples analysed Aim
Bulk characteristic CNS (LECO) All samples from all sites 432 subsamples analysed for C, N and S Characterization effect of treatments on bulk characteristics
Molecular approach carbohydrates (hot water extraction - GC) One profile from each situation 144 subsamples analysed for sugars content Effect of treatments on sugar content of peat in early regeneration stage
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1. Bulk indicator C water table effect
- In Baupte and Finland water table had no
significant effect on C
- In Scotland and Le Russey water table had a
significant effect on C
Finland
Le Russey
Ea Sf?
Baupte
Scotland
42
1. Bulk indicator C vegetation effect
- In Baupte and Scotland vegetation had no
significant effect on C
- In Finland and Le Russey vegetation had a
significant effect on C
Scotland
Le Russey
Finland
Baupte
43
1. Bulk indicator N vegetation effect
- Vegetation had no significant effect on N in
all sites
Scotland
Le Russey
Higher in surface peat
Primary production?
Finland
Baupte
44
1. Bulk indicator N Le Russey vs Baupte
Baupte
Le Russey
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2. Sugar analysis
Method As the substrate is rich in sugars, a
different method than those used in the WP1 (weak
and strong hydrolysis of peat on fine fraction)
had to be developed in order to illustrate
possible treatment effects at the molecular
level. Puget et al. (1999) showed, in mineral
soils, that a hot water extraction of
carbohydrates followed by an acid hydrolysis
could be used to detect monosaccharides
originated from microorganisms. This was the
first attempt to adapt this method to peat.
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2. Sugar analysis weak hydrolysis vs hot water
Low water table

Hot water extraction has a better potential than
weak hydrolysis to detect treatment effects

1. Increased proportions of Fucose, Allose,
   Rhamnose, Ribose microbe marker
2. Lower proportions of xylose vascular plant marker

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2. Sugar analysis results of glucose (µg g-1)
Hot water extractable Glucose between sites
Hot water extraction is able to detect site
differences with the most intensively exploited
site, Baupte, containing the lowest amount of hot
water extractable glucose
48
-WP2 C/N increase with depth at FR and FB and
decrease with depths at FI and Sc due to relative
high N at the surface of French sites (Vegetation
at Le Russey and allochtonous input in Baupte?)
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D16 Experimental assessment of decomposition
kinetics   Protocol to study the fate of organic
C and N in the peat using labelling technics (WP
III)     Principle - peat columns in laboratory
experiment with 15N-13C labelled litters - peat
columns in field experiment with 15N-13C labelled
litters - 3 plant litters - Sphagnum fallax
(mixture of capitula stems and leaves) - E.
vaginatum - E. angustifolium       Litter bag
system in the field The labelled litters were
dried and inserted in fine-meshed litterbags that
covered the whole surface of the pots that were
put in the experimental trenches. The in-situ
insertion was started between mid-July and
beginning of August. Because of the lack in
litter, new plants had to be grown to get enough
litter material.    
WP3
 
    - 3 replicates (3 trenches) for          3
plant litters          3 water levels - harvest
date 12 months after in situ incubation
starting (July-August 2004)  
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Litter system in the lab Conditions of
incubation 16/8 hours day/night
photoperiod 80 humidity air saturation Air
temperature 18C day, 12 C night  
Device
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Labelled litter 13C - 15N
Peat column
Harvest dates - laboratory experiment 15, 60
and 180 days (6 months) after initiation of
incubation   Measurement of CO2, CH4, N2O
emissions - at 1, 2, 5, 7, 15, 60 days -
directly in the jar by clapping the cap and
sampling through the septum as following
                            Compartments
which should be analysed in the field experiment
- litter, peat layers 0-5 cm, 5-15 cm, 15-25
cm For each depth soluble organic matter in
K2SO4, microbial biomass, peat stock, mineral
N 13C PLFA microbial communities (Münich),
                                             
towards microbes
Microbial communities 13C PLFA analysis   13C
15N in microbial biomass
towards peat
15N mineralization
13C 15N (K2SO4 extract without fumigation)
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Preliminary results on N transformations (lab
experiment)   15N method Calculation of the N
recovery For each selected compartment (peat, N
mineral, microbial biomass, etc.), the recovery
from the N input is calculated as R
(Ei/Eo) (Ni/a) 100   with Ni N stock of the
compartment i a N mass of the input (litter at
the start of the experiment) Ei isotopic excess
of the compartment i Eo isotopic excess of the
input
Ei/Eo corresponds to the N proportion coming from
the labeller. This corresponds to what is called
Ndff (Nitrogen derived from fertilizer (Powlson
Barraclough 1993, Guiraud Boniface 1987)
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