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Laboratoire des Interactions Ecotoxicologie, Biodiversité, Ecosystèmes

Laboratoire des Interactions Ecotoxicologie, Biodiversité, Ecosystèmes UMR CNRS 7146, Paul Verlaine-Metz University FRANCE. Evidence for a link between decomposer diversity and functional process of organic matter decomposition. Gierlinski Pierre , Guérold F., Wagner P., Rousselle P.

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Laboratoire des Interactions Ecotoxicologie, Biodiversité, Ecosystèmes

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  1. Laboratoire des Interactions Ecotoxicologie, Biodiversité, Ecosystèmes UMR CNRS 7146, Paul Verlaine-Metz UniversityFRANCE Evidence for a link between decomposer diversity and functional process of organic matter decomposition Gierlinski Pierre, Guérold F., Wagner P., Rousselle P.

  2. Introduction Worrying loss of species Freshwater ecosystems are among the most threatened Alterations of water chemistry (e.g. anthropogenic acidification)  diversity of aquatic organisms (Guerold et al, 2000; Driscoll et al, 2001) functional processes (Loreau et al, 2002; Baudoin et al, 2007)  Stream detritus food webs

  3. Ecological Functioning of forested headwater streams FPOM Fine Particulate Organic Matter Allochtonous organic matter Trophic Interactions Leaching Leaf-litter Microbial conditioning Decomposers Shredders Hyphomycetes Leaf-litter breakdown: Key process in forested headwater streams Filterers Collectors FPOM Predators

  4. Aims of the study How deeply a functional process is linked to biodiversity? • Test whether hyphomycete diversity has an effect on: • The production of Fine Particulate Organic Matter (FPOM) from leaf-litter • The palatability of leaf detritus for shredders

  5. Terms of the study Functional process: Leaf-Litter decomposition (3 leaves species) Biodiversity: Aquatic hyphomycete associated with decaying leaves Perturbationwhichcould induce diversity changes: Anthropogenic acidification

  6. Study area Vosges Mountains, France (NE) Donon Sandstone Ventron Granit 8 headwater streams pH and Al gradient

  7. Study area La Plaine LM (pH = 6,94) Sandstone bedrock LaMaix Ravines Basse des Escaliers RV (pH = 5,21) BE (pH = 4,40) Le Grand Bras 500 m Gentil Sapin GS (pH = 4,58)

  8. TH (pH = 6,64) • Study area Tihay 500 m Granitic bedrock GC (pH = 5,95) Le Grand Clos WS (pH = 5,11) Le Rouge-Rupt Wassongoutte LF (pH = 5,47) Longfoigneux

  9. Field experiment Leaf bag Air-dried 3 (± 0.03) g of dried leaves enclosed in 0.05 mm plastic mesh bags Alder, Maple and Beech leaves Exposure time (days): 3 bags randomly retrieved from the 8 streams after different exposure time + Physicaland chemical analyses

  10. FPOM Production and palatability experiments in microcosmes Leaf bag 5 shredders (Gammarus fossarum) 5 leaf disks (10 mm Ø) 5 leafdisks(10 mm Ø) + Spore suspension (20 ml) 3 replicates Incubation: 48 h at 10 °C Filtered water (0,45mm) from the correspondingstreams FPOM production (0,45mm) Leaf disk consumption

  11. NO3–SO4 F2 = 25.76 % Altot GS BE Conductivité LM RV S cations ANC F1 = 66,38 % WS LF GC TH pH • Results PCA on the physico-chemical variables a. b. NO3–SO4 Acid Sandstone Intermediate Acidity Altot Circumneutral S cations ANC Granit c. F1 = 66.38 %F2 = 25.76 %F3 = 6.03 %F4 = 1.29 %F5 = 0.48 %F6 = 0.03 % Acidity The F1 x F2 factorial plane explains 92.14 % of the total variance.

  12. Sandstone Granit • Results Leaf-litter decomposition * AFDM remaining (%) ** * Acid Alder Alder * Intermadiate acidity Circumneutral * * Acidic conditions =Lower decomposition rates (ANCOVA; a<0.005) AFDM remaining (%) ** * Maple Maple Decomposition rates significantly different among the tree species (ANCOVA; a<0.005) * * ** AFDM remaining (%) Beech Beech Time (days) Time (days)

  13. Results NMDS Plot on hyphomycete assemblages Intermediate Acidity Acid Circumneutral 7 sp Alder Beech Maple 14 sp 24 sp Stress = 0.006

  14. Sandstone Granit • Results Alder Alder FPOM Production FPOM (mg g-1 AFDM day-1) 0 FPOM production reduced under acidic conditions (ANOVA ; a<0.005) RV GS BE LM GC WS LF TH Maple Maple FPOM (mg g-1 AFDM day-1) FPOM production rise with time 0 RV GS BE LM GC WS LF TH x 2 x 3 Beech Beech Beech < Maple < Alder FPOM (mg g-1 AFDM day-1) 0 GC WS LF TH RV GS BE LM

  15. Sandstone Granit • Results Alder Alder Leaf disks consumption Daily consumption (mg AFDM g-1 day-1) Litter consumption reduced under acidic conditions (ANOVA ; a<0.005) RV GS BE LM GC WS LF TH Maple Maple Daily consumption (mg AFDM g-1 day-1) Leaf disk consumption rise with time RV GS BE LM GC WS LF TH Beech Beech Alder > Maple > Beech Daily consumption (mg AFDM g-1 day-1) GC WS LF TH RV GS BE LM

  16. Results FPOM production VS cumulated richness Beech Alder Maple FPOM (mg g-1 AFDM day-1) R² = 0,8669 * R² = 0,9102 R² = 0,8299 Cumulated richness (number of species) Strong relationship between diversity and FPOM production Lower FPOM production on beech litter (ANCOVA, a=0.005)

  17. Results Leaf disks consumption VS cumulated richness Beech Alder Maple Daily consumption (mg AFDM g-1 day-1) * R² = 0,6946 R² = 0,6685 R² = 0,9038 Cumulated richness (number of species) Strong relationship between diversity and leaf disks consumption Lower consumption of beech litter (ANCOVA, a=0.005)

  18. Exemple for Maple leaf-litter: Spore Biomass Richness FPOM (mg g-1 AFDM day-1) R² = 0,9102 R² = 0,12 R² = 0,117 Total number of spores Number of species Fungal biomasse (mg) / leave (g) Daily consumption (mg AFDM g-1 day-1) R² = 0,154 R² = 0,006 R² = 0,9038

  19. Discussion Field decomposition: Leaf-litter breakdown severely depressed under acidic conditions (Dangle & Guérold, 2001; Dangle et al, 2004; Baudoinet al, 2007) Marked differences in aquatic hyphomycete assemblages FPOM Production closely related with cumulated richness Rising with time  Importance of the species succession Reduced under acidic conditions  lower diversity  Adverse conditions for hyphomycetes? Exoenzymatic activity? (Jenkins & Subberkropp, 1995; Baudoin et al, 2007)

  20. Discussion Leaf disks consumption increase with time  microbial conditioning   palatability for the shredders Leaf-litter conditioned in the acidic streams: exhibited poor hyphomycete assemblages  poor palatability for the shredders Influence of the leaf-litter species • For the same level of diversity, different level of performances • Leaf-litter quality influences the energy flow in headwater streams

  21. Conclusions • The diversity of hyphomycete assemblages has an effect on: • Fine Particulate Organic Matter (FPOM) production from leaf-litter • The palatability of leaf detritus for shredders Manipulation of biodiversity by Acidification and Time  Organic matter decomposition in acidified stream is a good model to study the diversity-function relationships

  22. Thanks for your attention Gierlinski Pierre, Guérold F., Wagner P., Rousselle P.

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