Evidence for a link between decomposer diversity and Evidence for a link between decomposer diversity and functional process of organic matter decompositionfunctional process of organic matter decomposition

Laboratoire des Interactions Ecotoxicologie, Biodiversité, Ecosystèmes

UMR CNRS 7146, Paul Verlaine-Metz UniversityFRANCE

Gierlinski Pierre, Guérold F., Wagner P., Rousselle P.

IntroductionIntroduction

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 streamsEcological Functioning of forested headwater streams

Trophic Interactions

FPOM Fine Particulate Organic Matter

Microbial conditioning

FPOMFilterersFilterersCollectorsCollectors PredatorsPredators

Allochtonous organic matterAllochtonous organic matter

HyphomycetesHyphomycetes

DecomposersDecomposers

ShreddersShredders

Leaf-litterLeaf-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 studyAims 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 studyTerms of the study

Donon

Ventron

Vosges Mountains, France (NE)

8 headwater streams

pH and Al gradient

Study areaStudy area

Sandstone

Granit

La Maix

Basse des Escaliers

Gentil Sapin

La Plaine

Le G

rand

Bra

s

500 m

LM (pH = 6,94)

BE (pH = 4,40)

GS (pH = 4,58)

Sandstone bedrockSandstone bedrock

Rav

ines

RV (pH = 5,21)

Study areaStudy area

500 m

Le G

rand

Clo

s

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 areaStudy 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 experimentField experiment

Alder Maple Beech

14 21 28

35 42 56

49 63 70

77 77 77

Leaf bag

Exposure time (days):

FPOM Production and palatability experiments in microcosmes FPOM Production and palatability experiments in microcosmes

5 leaf disks (10 mm ØØ)

5 shredders (Gammarus fossarum)

3 replicates

Incubation: 48 h at 10 °C

Filtered water (0,45m) from the corresponding streams

5 leaf disks (10 mm ØØ)

Leaf disk consumptionFPOM production (0,45m)

+Spore

suspension (20 ml)

Leaf bag

ResultsResults

pH

Conductivité

ANC

Altot

cations

NO3–SO4

F1 = 66.38 %F2 = 25.76 %F3 = 6.03 %F4 = 1.29 %F5 = 0.48 %F6 = 0.03 %

BE

GC

GS

LF

LM RV

TH

WS F1 = 66,38 %

F2

= 2

5.76

%

The F1 x F2 factorial plane explains 92.14 % of the total variance.

a. b.

c.

PCA on the physico-chemical variables

Sandstone

Granit

Acid

Circumneutral Intermediate Acidity

ANC ANC

cations cations

Altot Altot

NO3–SO4 NO3–SO4

ResultsResults

**

*

*

*A

FD

M r

emai

ning

(%

)

Maple Maple

AF

DM

rem

aini

ng (

%)

**

*

*

*Alder Alder

Sandstone Granit

Acidic conditions =

Lower decomposition rates(ANCOVA; <0.005)

Decomposition rates significantly different

among the tree species(ANCOVA; <0.005)

Leaf-litter decomposition

** *

AF

DM

rem

aini

ng (

%)

Time (days)Time (days)

Beech Beech

*

Acid

Intermadiate acidity

Circumneutral

ResultsResults NMDS Plot on hyphomycete assemblages

AlderAlder

BeechBeech

MapleMaple

AcidIntermediate

Acidity

Stress = 0.00624 sp

14 sp

7 sp

ResultsResults

FPOM Production

Maple MapleF

PO

M (

mg

g-1 A

FD

M d

ay-1

)

0

Alder Alder

Sandstone Granit

FP

OM

(m

g g

-1 A

FD

M d

ay-1

)

0

Beech Beech

FP

OM

(m

g g

-1 A

FD

M d

ay-1

)

0

FPOM production reduced under

acidic conditions(ANOVA ; <0.005)

FPOM production rise with time

Beech < Maple < Alder

x 2 x 3

BE GS RV LM LF WS GC TH

BE GS RV LM LF WS GC TH

BE GS RV LM LF WS GC TH

ResultsResults

Leaf disks consumption

Alder Alder

Sandstone Granit

Da

ily c

on

sum

ptio

n (

mg

AF

DM

g-1 d

ay-1

)

Maple MapleD

aily

co

nsu

mp

tion

(m

g A

FD

M g

-1 d

ay-1

)

Beech Beech

Da

ily c

on

sum

ptio

n (

mg

AF

DM

g-1 d

ay-1

)

Litter consumption reduced under

acidic conditions(ANOVA ; <0.005)

Leaf disk consumption rise

with time

Alder > Maple > Beech

BE GS RV LM LF WS GC TH

BE GS RV LM LF WS GC TH

BE GS RV LM LF WS GC TH

ResultsResults FPOM production VS cumulated richness

*

Alder Maple Beech

FP

OM

(m

g g

-1 A

FD

M d

ay-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

ResultsResults Leaf disks consumption VS cumulated richness

Lower consumption of beech litter (ANCOVA, =0.005)

*

Alder Maple Beech

Cumulated richness (number of species)

Dai

ly c

on

su

mp

tio

n (

mg

AF

DM

g-1 d

ay-1)

Strong relationship between diversity and leaf disks consumption

R² = 0,6685

R² = 0,6946

R² = 0,9038

FP

OM

(m

g g

-1 A

FD

M d

ay-1

)

Richness Spore

Dai

ly c

on

su

mp

tio

n (

mg

AF

DM

g-1 d

ay-1)

Biomass

Number of species Fungal 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

DiscussionDiscussion

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

DiscussionDiscussion

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

ConclusionsConclusions

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 attentionThanks for your attention

Gierlinski Pierre, Guérold F., Wagner P., Rousselle P.