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

Introduction Introduction 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) Freshwater ecosystems are among the most threatened Worrying loss of species  Stream detritus food webs

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

Test whether hyphomycete diversity has an effect on: 1)The production of Fine Particulate Organic Matter (FPOM) from leaf-litter 2)The palatability of leaf detritus for shredders Aims of the study Aims of the study How deeply a functional process is linked to biodiversity?

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

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

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

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

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

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

Results pH Conductivité ANC Al tot  cations NO 3 –SO 4 F1 = % F2 = % F3 = 6.03 % F4 = 1.29 % F5 = 0.48 % F6 = 0.03 % BE GC GS LF LM RV TH WS F1 = 66,38 % F2 = % The F1 x F2 factorial plane explains % of the total variance. a.b. c. PCA on the physico-chemical variables Sandstone Granit Acid Circumneutral Intermediate Acidity ANC  cations Al tot NO 3 –SO 4

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

Results NMDS Plot on hyphomycete assemblages AlderBeech Maple Acid Intermediate Acidity Circumneutral Stress = sp 14 sp 7 sp

Results FPOM Production Maple FPOM (mg g -1 AFDM day -1 ) 0 Alder SandstoneGranit FPOM (mg g -1 AFDM day -1 ) 0 Beech FPOM (mg g -1 AFDM day -1 ) 0 FPOM production reduced under acidic conditions (ANOVA ;  <0.005) FPOM production rise with time Beech < Maple < Alder x 2 x 3 BEGSRVLM LFWSGCTH BEGSRVLM LFWSGCTH BEGS RV LM LFWSGCTH

Results Leaf disks consumption Alder SandstoneGranit Daily consumption (mg AFDM g -1 day -1 ) Maple Daily consumption (mg AFDM g -1 day -1 ) Beech Daily consumption (mg AFDM g -1 day -1 ) Litter consumption reduced under acidic conditions (ANOVA ;  <0.005) Leaf disk consumption rise with time Alder > Maple > Beech BEGSRVLM LFWSGCTH BEGSRVLM LFWSGCTH BEGS RV LM LFWSGCTH

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

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

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

Discussion Field decomposition: Leaf-litter breakdown severely depressed under acidic conditions (Dangle & Guérold, 2001; Dangle et al, 2004; Baudoin et al, 2007) 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) Marked differences in aquatic hyphomycete assemblages

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 For the same level of diversity, different level of performances  Leaf-litter quality influences the energy flow in headwater streams Influence of the leaf-litter species

Conclusions The diversity of hyphomycete assemblages has an effect on: 1)Fine Particulate Organic Matter (FPOM) production from leaf-litter 2)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

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