recipe meeting may 29 th -31 th aberdeen, scotland wp05: physico-chemical quality of peat om d 18:...

RECIPE meetingMay 29th-31th Aberdeen,

Scotland

WP05: physico-chemical quality of peat OM

D 18: Physico-Chemical characterisation of

the Organic Matter (OM) - ISTO


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)

Old peat Composed of - microbial secretions - humified materials - structureless tissues

1) Heterogeneous inherited tissues tend to become more homogeneous (dominance of Sphagna)

2) Increase of percentages of humified materials and microbial secretions.

New regenerating peat

Sp.Sp.Sp.Pol.

Er. Pol.Er.

AOM

Sp.

Muc

AOM AOMMuc

Muc

AOM

Muc

1. Bulk indicator: Microremain counts All sites pooled

1. CryoSEM: Texture of Le Russey bulk peat

Evolution of the bare peat surface along a trend of regeneration

Bare peat Eriophorum species

New peat (25years) Intact

- Bare peat => Impact of the exploitation

Bulk density (g/cm3)

0,00

0,04

0,08

0,12

0,16

0,20

0-5 yrs Bare 0-5 yrs Erio 25 yrs Mixed Intact >50 yrs

FRA FRB

FRC FRD

5µm 5µm

5µm 5µm

- Texture at 25yrs ≈ intact

Higher biodegradation in early regenerating stages than in the advanced ones

1. CryoSEM: Microorganisms (Le Russey)

- At surface peat => high diversity, high abundance

- At depth => low diversity (bacteria), low abundance

SURFACE

DEPTH

SURFACE SURFACE

DEPTH

10µm

2µm

12µm 3.75µm

3µm

Same diversity in November 2001,

2003 and June 2005

2. Bulk indicator: atomic C/N bulk

5-10 years

0

10

20

30

40

50

60

70

80

3 4 6 8

FB

FR + CH

FI

SC

- C/N of FI & SC > FR+CH > FB-in upper level: 20 < C/N < 40- downward: 40 < C/N < 60

0

10

20

30

40

50

60

70

80

3 4 6 8

FB

FR + CH

FI

SC

Higher C/N in regenerating peat (25 and 50 years) showing effect of regeneration on bulk chemical characteristics of peat

Intact and > 50 years

25-45 years

0

10

20

30

40

50

60

70

80

3 4 6 8

FB

FR + CH

FI

SC

Boundary between old and new peat

BaupteJura sitesFinlandScotland

3 : 2.5 cm

4 : 7.5 cm

6 : 25 cm

8 : 45 cm

0

100

200

300

400

3 4 6 8

FB

FR + CH

FI

SC

3. Molecular indicators: Total sugars

0

100

200

300

400

3 4 6 8

FB

FR + CH

FI

SC

0

100

200

300

400

3 4 6 8

FB

FR + CH

FI

SC

5-10 years

Intact and > 50 years

25-45 years

Fine-grained fraction < 200 µm (strong hydrolysis)

High total sugar content, except for FB

No difference between recent and advanced regeneration stages:Recent regenerating stage => TS 200mg/g In advanced stage => TS 200 mg/g

but within a profile total sugar content can reflect the difference between « new » and « old » peat

mg/g mg/g mg/g

BaupteJura sitesFinlandScotland

3 : 2.5 cm

4 : 7.5 cm

6 : 25 cm

8 : 45 cm

Mixed vegetation 50 years

0102030405060

Arabin

ose

Rham

nose

Ribos

e

Fucos

e

Man

nose

Galacto

se

Xylos

e

Gluco

se

2.5 cm

7.5 cm

25 cm

45 cm

Eriophorum 10 years

0

10

20

30

40

50

60

Arabino

se

Rhamno

se

Ribose

Fucos

e

Man

nose

Galacto

se

Xylose

Glucos

e

litter

2.5 cm

7.5 cm

25 cm

45 cm

Sphagnum 10 years

0

10

20

30

40

50

60

Arabino

se

Rhamno

se

Ribose

Fucos

e

Man

nose

Galacto

se

Xylose

Glucos

e

2.5 cm

7.5 cm

25 cm

45 cm

rhamnose and galactose are

markers of Sphagnum species

xylose and arabinose are

markers of Vascular plants

Analysis of sugars can record influence of both

plants

WP 1: Recording of source materials in a regeneration trend (mg g-1) at the Scottish site

63 µm < fraction < 200 µm (weak hydrolysis)

bare peat 5 years

0102030405060

Arabin

ose

Rham

nose

Ribos

e

Fucos

e

Man

nose

Galacto

se

Xylos

e

Gluco

se

2.5 cm

7.5 cm

25 cm

45 cm

WP 1: Evolution of microremains during regeneration at the Scottish site

Bare peat 5 years

2.5 cm

25 cm

7.5 cm

45 cm

2.5 cm

25 cm

7.5 cm

45 cm

2.5 cm

25 cm

7.5 cm

45 cm

0 cm

2.5 cm

25 cm

7.5 cm

45 cm

Sphagnum 10 years

Eriophorum 10 years

Mixed vegetation 50 years

Dominance of mucilage in bare peatIncreasing amount of

preserved Sphagnum tissues (low AOM)

Dominance of AOM

and unspecified tissues

Microremans reflect input from

both vegetation as sugars

WP 1: Influence of the water table on sugar content (%) in wet and dry Eriophorum situations in Finland (weak hydrolysis)

63 µm < fraction < 200 µm

Eriophorum vaginatum wet

0%10%20%30%40%50%60%70%80%90%

100%

plant litter 0-5cm

5-10cm

22.5-27.5cm

42.5-47.5cm

Glucose H

Xylose

Galactose

Mannose

Fucose

Ribose

Rhamnose

Arabinose

Eriophorum vaginatum dry

0%10%20%30%40%50%60%70%80%90%

100%

plant litter 0-5cm

5-10cm

22.5-27.5cm

42.5-47.5cm

Glucose H

Xylose

Galactose

Mannose

Fucose

Ribose

Rhamnose

ArabinoseCan relative sugar content reflect changes in microbial communities

structure after rewetting??

Analyses of sugars are able to reflect chemical changes of peat induced by

rewetting: higher degradation of the litter in dry conditions

*Relative amount of sugars originated from the plant, Xyl and Ara, are lower in dry conditions than in wet conditions (higher Hemi Glu)

*

*

*

*

# Microbial markers:

-Fucose more abundant in wet situation than in dry situation

-Rhamnose and mannose more abundant in dry situation

#

#

WP 1: Influence of time on sugar content (%) in Sphagnum fallax situations in Scotland (weak hydrolysis)


Sphagnum fallax 10 years

0%10%20%30%40%50%60%70%80%90%

100%

plant 5-10cm

12.5-17.5cm

22.5-27.5cm

32.5-37.5cm

Glucose H

Xylose

Galactose

Mannose

Fucose

Ribose

Rhamnose

Arabinose

Sphagnum fallax 50 years

0%10%20%30%40%50%60%70%80%90%

100%

plant 0-5 cm 5-10cm

12.5-17.5cm

Glucose H

Xylose

Galactose

Mannose

Fucose

Ribose

Rhamnose

Arabinose

Compared to Eriophorum, sugar content of peat tend

to be similar to the composition of the source

material

Better preservation of Sphagnum than Eriophorum

Work Program 1: D 18

Physico-chemical characteristics of peat: differences

between « old » and « new » peat

=> 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 > 0.15g.m-3),

- Lower C/N ratios (20-30).

=> Indicators of the new regenerating peat show:

- Microremains dominated by preserved tissues, especially from Sphagnum

- Low compaction (bulk density < 0.05g .m-3)

- Higher C/N ratios (30-45)

Work Program 1: D 18

Physico-chemical characteristics of peat: dynamics of OM

qualityMicroremain 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

- Similar 1st steps of regen. for Jura & Scotish sites => similar plant compositions of new peat (mainly Sphagna)- Distinct evolution for F=> « 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

Schematic model of peat evolution of chemical characteristics from new to old

peat in the different sites3 trends : Jura sites, Scottish sites, Finish sites

33%

21%

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)


Scotland


D 18 – WP2

CNS results

Sugars analysis results

1. Bulk indicator: site effect on C/NChemical 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%

Boxplot by Group

Variable: C/N atomic

Mean ±SE ±1.96*SE

Le Russey Baupte Finland Scotland

Country

25

30

35

40

45

50

55

60

65C

/N a

tom

ic

C/NKruskal-Wallis

Le Russey Finland

H P H P

Water table 1.51 0.47 Water table 1.94 0.38

Vegetation 0.79 0.85 Vegetation 4.44 0.22

Depth 40.4 < 0.0001 Depth 24.1 < 0.0001

Baupte Scotland

H P H P

Water table 0.04 0.98 Water table 3.36 0.19

Vegetation 2.34 0.51 Vegetation 0.77 0.43

Depth 57.9 < 0.0001 Depth 13.7 0.001

Tend to increase with depth

Tend to decrease with

depth

1. Bulk indicator: C/N depth effect

Higher N content at the surface

1. Bulk indicator: water table (WT) and vegetation (Veg) effect

-In Baupte and Finland:

WT no significant effect on C%

-In Scotland and Le Russey:

WT significant effect on C%

(other than low situation at FR, tend to increase with WT)

- In Baupte and Scotland:

Veg no significant effect on C%

-In Finland and Le Russey:

Veg significant effect on C%

(FR: low in Ev and high in Sf, FI: high in Ea and low in SF)

Low water table

0 0.5 1 1.5 2 2.5

0-5 cm

12.5-17.5 cm

32.5-37.5 cm

Bare peat

E. vag

Low water table

0 0.5 1 1.5 2 2.5

0-5 cm

12.5-17.5 cm

32.5-37.5 cm

Bare peat

E. vag

Le Russey Baupte

- In all sites: Veg had no significant effect on N%, but:

Kruskal Wallis testing main effects

1. Bulk indicatorBulk 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

Finland

Baupte

Scotland

Le Russey

Response of C and N content to water table and vegetation seems to depend on peat type (site

characteristics) and history of exploitation

Increase of sensitivity to treatments

Eriophorum vaginatum

0

5

10

15

20

25

30

35

40

Xylose

Allose

Fucose

Ribose

Rhamnose

7%

Bare peat

0

5

10

15

20

25

30

35

40

Xylose

Allose

Fucose

Ribose

Rhamnose 1) Compared to bare peat, E. vag tended to increase the proportion of sugars derived from microbial synthesis and/or root exudates

1)

%

S. fallax

0

5

10

15

20

25

30

35

40

Xylose

Allose

Fucose

Ribose

Rhamnose

2. Sugar analysis: FI low water table – 12.5 cm

2) Under S. fal, among the microbe markers, only fucose tended to increase slitghtly (rhamnose is also a marker of Sphagnum sp)

2)

Analysis of hot water extractable sugars detects changes caused by

plant colonisation better than weak hydrolysis

Impact of plant on microbial activity?

%

%

Weak hydrolysis Hot water extraction

6%

8%

Hot water extraction versus weak hydrolysis – extract the most labile sugars newly synthesized

2. Sugar analysis: problem encountered

FI LO EV5-2 11/2005

0.E+00

5.E+06

1.E+07

2.E+07

0 1000 2000 3000 4000 5000 6000 7000

FI LO EV5-2 03/2006

1.E+06

2.E+06

3.E+06

4.E+06

0 1000 2000 3000 4000 5000 6000 7000

IS

Hot water extractable sugars are very sensitive to storage condition

November 2005

March 2006

Disappearance of known peaks

AR

X+FGa

MG

G

IS

IS IS

Appearance of many unknown

peaks

2. Sugar analysis: vegetation effect on glucose

(µg g-1)

0

200

400

600

800

1000

LeRussey

Scotland Finland Baupte

bare peat

E. ang

E. vag

S. fal

In other sites than Baupte, Eriophorum situation tend to contain more hot water extractable glucose

Plant effect may differs between site in long term?

E. ang in Le Russey and Scotland

E. vag in Finland

2. Sugar analysis: water table effect on glucose

0

200

400

600

800

1000

Le Russey Scotland Finland Baupte

Low

Medium

High

In other sites than Baupte, water table tend to affect hot water extractable glucose

Site may respond differently to water table in long term?

Increase with WT in Le Russey and Scotland

Decrease with WT in Finland

(µg g-1)

2. Sugar analysis: depth effect on glucose

0

200

400

600

800

1000


-2.5 cm

-15 cm

-35 cm

Trend of hot water extractable glucose with depth tend to be different between site

Spatial distribution of hot water extractable glucose differs between site in long term?

Decrease with depth in Le Russey and Scotland

Constant in Finland

(µg g-1)

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

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

- methodological difficulties (storage)

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

WP 1 and WP 2 General synthesisAge effectMicroremain 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:

1) at Le Russey, by Cryo SEM with the observation of more degraded tissues in early than advanced stages at the same depth (WP1),

2) at the Finnish site, with sugars analysis => higher preservation of Sphagnum than Eriophorum (WP1),

3) N% tend to be higher under Eriophorum in FR, FI and SC at the surface => 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)

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.

Involvement of OM characterisation in the process of exploited site rehabilitation

1) Characterisation of the exploited site

2) Definition of a reference system (carbon storage)

3) Assess the gap between site to manage and reference system

4) Choice of management

5) Survey

Bulk analysis

Microremains analysis

Sugar analyses

As bulk analyses

such as C/N do not provide detailed

informaton on peat qualityAs sugar content

maybe too expensive to implement

Microremain counts is the best

technique to characterise the OM

of a site and undertake survey

Bulk analysis

Microremains analysis

Sugar analyses

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

Problems encountered in the interpretation of OM data

WP 1Too 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 2Short 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)

1. Micromorphology : OM diagenesis

more rapid peat degradation in the first regenerating stage than in the advanced stage

0-5 yrs – Eriophorum 25 yrs – Mixed vegatation Intact

An example of le Russey site: transverse section of Sphagna stems in below litter compartment

Thick well-preserved cell walls with filled cavities

fine cell walls with empty cavities

Intermediate degradation stage

FRB FRC

37.5µm 20µm 27.3µm

FRD

Jura : 5-10 years

0

20

40

60

80

100

120

140

bulk <200 µm

C/N

Baupte 5-10 years

0

20

40

60

80

100

120

140

bulk <200 µm

C/N

Scotland : 5-10 years

0

20

40

60

80

100

120

140

bulk <200 µm

C/N

Finland : 5-10 years

0

20

40

60

80

100

120

140

bulk <200 µm

C/N

Jura INTACT > 50 years

0

20

40

60

80

100

120

140

bulk <200 µm

C/N

Scotland : 50 years

0

20

40

60

80

100

120

140

bulk <200 µm

C/N

Finland : 50 years

0

20

40

60

80

100

120

140

bulk <200 µm

C/N

Jura Scotland

FinlandBaupte

Jura (Intact) Scotland

Finland

5-10 years

50 years

2. Bulk indicator: C/N – Bulk/Fine fraction

No differences of the C/N ratio

between these both fractions

2. Bulk indicator: C/N – diverse fractions

0

20

40

60

80

100

120

140

> 1mm <1mm <200µm <63µm

0

20

40

60

80

100

120

140

>1mm < 1mm < 200µm < 50 µm

0

20

40

60

80

100

120

140

>2mm <2mm <200µm < 50 µm

Scotland

Finland

5-10 years

50 years

Finland

Scotland

0

20

40

60

80

100

120

140

>1mm < 1mm < 200µm < 50 µm

Significance differences in

3. Molecular indicators: Total sugars An example of le Russey, comparaison of sugars in bulk peat and in the fine-grained fraction <200µm

Bulk

0

10

20

30

40

50

Ara Rha Rib Fuc Man Gal Xyl Gluc

2,5

7,5

15

25

35

45

< 200 µm

0

10

20

30

40

50


2,5

7,5

15

25

35

45

Bulk

0

10

20

30

40

50


2,5

7,5

15

25

35

45

< 200 µm

0

10

20

30

40

50


2,5

7,5

15

25

35

45

Intact > 50 years

25 years

% %

% %

WP 1: Evolution of peat granulomtry during regeneration (mg g-1) at the Scottish site

Scotland bare peat (5 years)

0% 50% 100%

0-5 cm

5-10 cm

22.5-27.5 cm

42.47.5 cm

> 200 µm

< 200 µm

Scotland Sphagnum (10 years)

0% 50% 100%

0-5 cm

5-10 cm

22.5-27.5 cm

42.47.5 cm

> 200 µm

< 200 µm

Scotland mixed vegetation (50 years)

0% 50% 100%

0-5 cm

5-10 cm

22.5-27.5 cm

42.47.5 cm

> 200 µm

< 200 µm

Scotland Eriophorum (10 years)

0% 50% 100%

litter

0-5 cm

5-10 cm

22.5-27.5 cm

42.47.5 cm

> 200 µm

< 200 µm

Increase of the coarse- grained fraction in both vegetation compared to

bare peat

Increase amount of coarse-grained

fraction when both plants (mixed

vegetation) are allowed to interact for

a long time

WP 1: Influence of the water table on sugar content (mg g-1) in wet and dry Eriophorum situations in Finland


Eriophorum wet

0102030405060708090

Arabi

nose

Rhamnos

e

Ribos

e

Fucos

e

Man

nose

Galacto

se

Xylose

Gluco

se

litter

2.5 cm

7.5 cm

25 cm

45 cm

Eriophorum dry

0102030405060708090

Arabi

nose

Rhamnos

e

Ribos

e

Fucos

e

Man

nose

Galacto

se

Xylose

Gluco

se

litter

2.5 cm

25 cm

45 cm

1) Sugars markers of vascular plants are consumed in dry situation, whereas they tend to be conserved in wet environment2) 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??

WP 1: Influence of the water table on the peat granulometry in wet and dry Eriophorum situations in Finland

Finlande, Eriophorium vaginatum humide (10 ans)

0% 50% 100%

litter

0-0.5 cm

5-10 cm

22.5-27.5 cm

42.5-47.5 cm

> 200 µm

< 200 µm

Finlande, Eriophorum vaginatum sec (10 ans)

0% 50% 100%

litter

0-0.5 cm

5-10 cm

22.5-27.5 cm

42.5-47.5 cm

> 200 µm

< 200 µm

Coarse grained fraction is found in higher amounts in wet

conditions than in dry conditions

Water table affect the peat granulometry

reflecting degradation processes

0 cm

2.5 cm

25 cm

7.5 cm

45 cm

0 cm

2.5 cm

25 cm

7.5 cm

45 cm

Eriophorum wet Eriophorum dry

Poor indicator of water table

effect

Global similar macrorest profile between the two situation

WP 1: Influence of the water table on the macrorests

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

ISTO in the WP2

Level of analysisAnalysis (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

1. Bulk indicator: C% water table effect- In Baupte and Finland: water

table had no significant effect on C%

Boxplot by Group

Variable: C%

Mean ±SE ±1.96*SE

Low Medium High

Water table

49.2

49.4

49.6

49.8

50.0

50.2

50.4

50.6

50.8

C %

Boxplot by Group

Variable: C%

Mean ±SE ±1.96*SE

Low Medium High

Water table

50.8

51.0

51.2

51.4

51.6

51.8

52.0

52.2

C %

Boxplot by Group

Variable: C%

Mean ±SE ±1.96*SE

Low Medium High

Water table

50.5

51.0

51.5

52.0

52.5

53.0

53.5

54.0

C %

Boxplot by Group

Variable: C%

Mean ±SE ±1.96*SE

Low Medium High

Water table

47.8

48.0

48.2

48.4

48.6

48.8

49.0

49.2

49.4

49.6

C %

- In Scotland and Le Russey: water table had a significant

effect on C%Finland

Baupte Scotland

Le RusseyEa +Sf?

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%Boxplot by Group

Variable: C%

Mean ±SE ±1.96*SE

Bare peatE. angustifolium

E. vaginatumS. fallax

Vegetation

51.0

51.2

51.4

51.6

51.8

52.0

52.2

52.4

52.6

52.8

53.0

53.2

C %

Boxplot by Group

Variable: C%

Mean ±SE ±1.96*SE



Vegetation

50.4

50.6

50.8

51.0

51.2

51.4

51.6

51.8

52.0

52.2

52.4

C %

Boxplot by Group

Variable: C%

Mean ±SE ±1.96*SE



Vegetation

48.849.049.249.449.649.850.050.250.450.650.851.051.251.4

C %

Boxplot by Group

Variable: C%

Mean ±SE ±1.96*SE



Vegetation

47.8

48.0

48.2

48.4

48.6

48.8

49.0

49.2

49.4

49.6

49.8

C %

FinlandBaupte

Scotland Le Russey

Boxplot by Group

Variable: N%

Mean ±SE ±1.96*SE



Vegetation

1.181.201.221.241.261.281.301.321.341.361.381.401.421.441.46

N %

Boxplot by Group

Variable: N%

Mean ±SE ±1.96*SE



Vegetation

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

N %

Boxplot by Group

Variable: N%

Mean ±SE ±1.96*SE



Vegetation

1.361.38

1.40

1.42

1.44

1.46

1.48

1.50

1.52

1.54

1.56

1.58

1.60

N %

Boxplot by Group

Variable: N%

Mean ±SE ±1.96*SE



Vegetation

1.74

1.76

1.78

1.80

1.82

1.84

1.86

1.88

N %

1. Bulk indicator: N% vegetation effect - Vegetation had no significant effect on N% in all sites

FinlandBaupte

Scotland Le RusseyHigher in

surface peat

Primary production

?

High water table

0 0.5 1 1.5 2 2.5

0-5 cm

12.5-17.5 cm

32.5-37.5 cm

Bare peat

E. vag

Low water table

0 0.5 1 1.5 2 2.5

0-5 cm

12.5-17.5 cm

32.5-37.5 cm

Bare peat

E. vag

1. Bulk indicator: N% Le Russey vs Baupte

Low water table

0 0.5 1 1.5 2 2.5

0-5 cm

12.5-17.5 cm

32.5-37.5 cm

Bare peat

E. vag

High water table

0 0.5 1 1.5 2 2.5

0-5 cm

12.5-17.5 cm

32.5-37.5 cm

Bare peat

E. vag

Le Russey Baupte

2. Sugar analysisMethod:

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.

2. Sugar analysis: weak hydrolysis vs hot water

Eriophorum vaginatum

0

5

10

15

20

25

30

35

40

45

weakhydrolysis -

depth 3

hot water -depth 3

weakhydrolysis -

depth 5

hot water -depth 5

weakhydrolysis -

depth 7

hot water -depth 7

Xylose

Allose

Fucose

Ribose

Rhamnose

1) Increased proportions of Fucose, Allose, Rhamnose, Ribose: microbe marker

2) Lower proportions of xylose: vascular plant marker

Hot water extraction has a better

potential than weak hydrolysis to detect treatment effects

Low water table

%

2. Sugar analysis: results of glucose (µg g-1)

Hot water extractable Glucose between sites

Glucose

0

100

200

300

400

500

600

700

800


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

-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?)

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.

PVC tube in the field(trenches), filled with peat

PVC ring (about 5 cm height) : adjusted at the surface of the peat column inside the PVC tube (see black arrow)

fiber glass nets (= anti-mosquito curtain) with a 0.5 mm mesh size : 2 nets on upper and below openings (upper and below parts of the 5 cm height PVC cylinder)

peat surface in the trench

- 3 replicates (3 trenches) for 3 plant litters 3 water levels- harvest date : 12 months after in situ incubation starting (July-August 2004)

WP3

Litter system in the lab :Conditions of incubation :

16/8 hours day/night photoperiod80 % humidity air saturationAir temperature : 18°C day, 12 °C night

PVC tube in a jar with peat from Le Russey

Litter adjusted at the surface of the peat column inside the PVC tube (see black arrow)

fiber glass nets : see upper

Water-level in the jar

10 cm height

fiber glass net

Cap of the jar with a septum in the middle

6.5 cm diameter

Device :

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 cmFor each depth : soluble organic matter in K2SO4, microbial biomass, peat stock, mineral N13C PLFA microbial communities (Münich),

Gas Chromatograph

Labelled litter13C - 15N

15N mineralization

towards microbes

Microbial communities :13C PLFA analysis 13C & 15N in microbial biomasstowards peat

13C & 15N (K2SO4

extract without fumigation)

Peat column

Preliminary results on N transformations (lab experiment) 15N method – Calculation of the N recoveryFor 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)

recipe meeting may 29 th -31 th aberdeen, scotland wp05: physico-chemical quality of peat om d 18:...

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