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RECIPE meeting May 29 th -31 th Aberdeen, Scotland

WP05: physico-chemical quality of peat OM. RECIPE meeting May 29 th -31 th Aberdeen, Scotland. D 18: Physico-Chemical characterisation of the Organic Matter (OM) - ISTO. WP05: physico-chemical quality of peat OM. RECIPE meeting May 29 th -31 th Aberdeen, Scotland. D 18 - WP 1.

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RECIPE meeting May 29 th -31 th Aberdeen, Scotland

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  1. WP05: physico-chemical quality of peat OM RECIPEmeeting May 29th-31th Aberdeen, Scotland D 18: Physico-Chemical characterisation of the Organic Matter (OM) - ISTO

  2. WP05: physico-chemical quality of peat OM RECIPEmeeting 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)

  3. 1. Bulk indicator: Microremain counts New regenerating peat All sites pooled AOM AOM Muc AOM Muc Muc Pol. Sp. Sp. Sp. Sp. Pol. Er. 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 => 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

  5. 1. CryoSEM: Microorganisms (Le Russey) SURFACE SURFACE SURFACE 12µm 3.75µm 10µm • At surface peat => high diversity, high abundance Same diversity in November 2001, 2003 and June 2005 DEPTH DEPTH 3µm - At depth => low diversity (bacteria), low abundance 2µm

  6. Baupte Jura sites Finland Scotland Intact and > 50 years 25-45 years Higher C/N in regenerating peat (25 and 50 years) showing effect of regeneration on bulk chemical characteristics of peat • - C/N of FI & SC > FR+CH > FB • in upper level: 20 < C/N < 40 • downward: 40 < C/N < 60 Boundary between old and new peat 2.Bulk indicator: atomic C/N bulk 3 : 2.5 cm 4 : 7.5 cm 6 : 25 cm 8 : 45 cm 5-10 years

  7. Baupte Jura sites Finland Scotland 3.Molecular indicators: Total sugars 3 : 2.5 cm 4 : 7.5 cm 6 : 25 cm 8 : 45 cm Fine-grained fraction < 200 µm (strong hydrolysis) Intact and > 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 => 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

  8. 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)

  9. 2.5 cm Dominance of mucilage in bare peat 7.5 cm Increasing amount of preserved Sphagnum tissues (low AOM) 25 cm 0 cm 45 cm 2.5 cm 7.5 cm 2.5 cm 25 cm 7.5 cm 45 cm 25 cm Microremans reflect input from both vegetation as sugars 45 cm 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

  10. * *Relative amount of sugars originated from the plant, Xyl and Ara, are lower in dry conditions than in wet conditions (higher Hemi Glu) # * Analyses of sugars are able to reflect chemical changes of peat induced by rewetting: higher degradation of the litter in dry conditions • # Microbial markers: • Fucose more abundant in wet situation than in dry situation • Rhamnose and mannose more abundant in dry situation * # * Can relative sugar content reflect changes in microbial communities structure after rewetting?? 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

  11. Better preservation of Sphagnum than Eriophorum WP 1: Influence of time on sugar content (%) in Sphagnum fallax situations in Scotland (weak hydrolysis) 63 µm < fraction < 200 µm Compared to Eriophorum, sugar content of peat tend to be similar to the composition of the source material

  12. 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)

  13. Work Program 1: D 18 Physico-chemical characteristics of peat: dynamics of OM quality Schematic model of peat evolution of chemical characteristics from new to old peat in the different sites 3 trends : Jura sites, Scottish sites, Finish sites 21% 33% • Microremain counts in new peatshowed • 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 • => 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

  14. WP05: physico-chemical quality of peat OM RECIPEmeeting May 29th-31th Aberdeen, Scotland D 18– WP2 CNS results Sugars analysis results

  15. 1. Bulk indicator: site effect on C/N Chemical characterisation of the peat from each site: Scotland: higher C%, intermediate N% and S% Finland: Lower C%, intermediate N% and S% Baupte: Lower C%, higher N% and S% Le Russey: higher C%, lower N% and S%

  16. 1.Bulk indicator: C/N depth effect Tend to increase with depth Tend to decrease with depth Higher N content at the surface

  17. 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) 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

  18. 1.Bulk indicator Bulk analyses were able to: - show site and depth effect on C/N - record effect ofwater 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

  19. 1) Compared to bare peat, E. vag tended to increase the proportion of sugars derived from microbial synthesis and/or root exudates 1) 2) Under S. fal, among the microbe markers, only fucose tended to increase slitghtly (rhamnose is also a marker of Sphagnum sp) Analysis of hot water extractable sugars detects changes caused by plant colonisation better than weak hydrolysis Impact of plant on microbial activity? 2) 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

  20. Appearance of many unknown peaks Disappearance of known peaks 2.Sugar analysis: problem encountered November 2005 IS IS G R X+F G A M Ga March 2006 IS IS Hot water extractable sugars are very sensitive to storage condition

  21. E. ang in Le Russey and Scotland E. vag in Finland Plant effect may differs between site in long term? 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

  22. Increase with WT in Le Russey and Scotland Decrease with WT in Finland Site may respond differently to water table in long term? 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. Decrease with depth in Le Russey and Scotland Constant in Finland Spatial distribution of hot water extractable glucose differs between site in long term? 2.Sugar analysis: depth effect on glucose (µg g-1) Trend of hot water extractable glucose with depth tend to be different between site

  24. 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

  25. 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

  26. 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 => higher preservation of Sphagnum than Eriophorum (WP1), • 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)

  27. 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.

  28. 1) Characterisation of the exploited site 2) Definition of a reference system (carbon storage) Bulk analysis Microremains analysis Sugar analyses 3) Assess the gap between site to manage and reference system 4) Choice of management Bulk analysis Microremains analysis Sugar analyses Microremain counts is the best technique to characterise the OM of a site and undertake survey 5) Survey 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)

  31. 37.5µm 20µm 27.3µm 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 Intermediate degradation stage Thick well-preserved cell walls with filled cavities fine cell walls with empty cavities more rapid peat degradation in the first regenerating stage than in the advanced stage

  32. Finland : 50 years 140 120 100 80 C/N 60 40 20 0 bulk <200 µm 2.Bulk indicator: C/N – Bulk/Fine fraction 5-10 years 50 years Scotland Jura Jura (Intact) Scotland Finland Baupte Finland No differences of the C/N ratio between these both fractions

  33. 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 <200µm 25 years Intact > 50 years % % % %

  35. Increase of the coarse- grained fraction in both vegetation compared to bare peat 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 < fraction < 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. 0 cm 0 cm 2.5 cm 2.5 cm 7.5 cm 7.5 cm 25 cm 25 cm 45 cm 45 cm 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

  41. 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

  45. 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.

  46. 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 • Increased proportions of Fucose, Allose, Rhamnose, Ribose: microbe marker • Lower proportions of xylose: vascular plant marker

  47. 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?)

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

  50. Cap of the jar with a septum in the middle fiber glass nets : see upper Litter adjusted at the surface of the peat column inside the PVC tube (see black arrow) Water-level in the jar 10 cm height PVC tube in a jar with peat from Le Russey fiber glass net 6.5 cm diameter Litter system in the lab : Conditions of incubation : 16/8 hours day/night photoperiod 80 % humidity air saturation Air temperature : 18°C day, 12 °C night Device :

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