Soil fauna: Key to soil organicmatter dynamics and fertility?

P. LAVELLE, J.J. JIMENEZ, J. FILSER

Université Pierre et Marie Curie (IEES), France,

Instituto Pirenaico de Ecologia-CSIC, Spain

Universitat Bremen, Germany

SOM models fail to predict changes associated with global change

Basic assumptions

SOM dynamics a function of

• Climate (T° and moisture)

• Soil (clay and bulk density, FIXED)

• Litter composition (L/N)

Unable to predict persistence of SOM over time.Environmental and biological controlspredominate over molecular structure

Schmidt et al., Nature, 2011

The CENTURY model, Parton et al., 1983

Microbialbiomass

Physicallyprotected

Chemicallyprotected

Eight improvements to the models

J. Filser , J.J. Jimenez et al., submitted

vv vv

vvv

vvv

vvv

vvv

SOIL FAUNA?

Changes in paradigmsRecalcitrant SOM (« Passive soil pool »)

does not exist

The tropical earthworm Millsonia anomala digests all particle size fractions

with the same efficiency

As clay/humic compounds As humified compounds in deep soil

Priming Effect

Sleeping Beauty paradoxe

Lavelle, 1997

The power of Ecosystem Engineers

• Ecosystem Engineering byinvertebrates and roots• Control aggregation turnover

• Changes plant production and microbial communities

• Deepen the soil

• Accelerate plant successionalprocess

• Etc. Etc.

Signaling

Energe c

COMMUNITYENGINEERING

PHYSICALENGINEERING

BIOCHEMICALENGINEERING

WaterServices Primary

Produc on

Climatecontrol

Erosioncontrol

SoilPhysicalStructure

Microbial,Invert.Plantcommuni es

Decomposi onNutrientCycling

Hormones

MOSAICOF

FUNCTIONALDOMAINS

BiogenicStructures

EcologicalMediator

Source: Lavelle et al., Soil Science, 2016

V

V

V

Changes in paradigms

Physical Ecosystem engineers are diverse and numerous worldwide

4259 sites49 countries

The average soil macroinvertebratecommunity

Macrofauna database

Source: Lavelle et al., unp. data

18

SOM Stabilization by creation of structures

not considered in models

Functionalgroups

Spatial

distribution

Successional processes

. . .

SOMEffect on

COMMINUTIONASSIMILATION

RELEASENUTRIENT

PROTECTIONPHYSICAL ACCELERATION

OF TURNOVER

TimeStructure

HOURSGUT CONTENT

DAYS / WEEKS FRESH CASTS

YEARS : DECADESSOIL PROFILE

MONTHS AGEING CASTS

Source : Lavelle, 1997. An. Rev. Ecol. Evol.

Activation

of mineralisation ConservationTransfers

They alter the spatial and temporal patternsof SOM dynamics

1350 Mg ha-1 year-1

In the LAMTO savanna

F df p

Tree species 0.1 1 47 ns

Litter vs excrement 6.2 2 47 0.00475

Soil C content 13.0 1 47 0.00092

-10

-5

0

5

10

15

20

25

30

Alder L Oak L Alder Ex Oak Ex Alder GL Oak GL

Respira

tion c

han

ge

(ml C

O2 g

-1)

High C Low C

F df p

Tree species 0.1 1 47 ns

Litter vs excrement 6.2 2 47 0.00475

Soil C content 13.0 1 47 0.00092

-10

-5

0

5

10

15

20

25

30

Alder L Oak L Alder Ex Oak Ex Alder GL Oak GL

Respira

tion c

han

ge

(ml C

O2 g

-1)

High C Low C

F df p

Tree species 0.1 1 47 ns

Litter vs excrement 6.2 2 47 0.00475

Soil C content 13.0 1 47 0.00092

-10

-5

0

5

10

15

20

25

30

Alder L Oak L Alder Ex Oak Ex Alder GL Oak GL

Respira

tion c

han

ge

(ml C

O2 g

-1)

High C Low C

LITTER FECALPELLETS

Protection of SOM in fecal pellets of Bibio

Consume 40% of litter

F df p

Tree species 0.1 1 47 ns

Litter vs excrement 6.2 2 47 0.00475

Soil C content 13.0 1 47 0.00092

-10

-5

0

5

10

15

20

25

30

Alder L Oak L Alder Ex Oak Ex Alder GL Oak GL

Respira

tio

n c

han

ge

(ml C

O2 g

-1)

High C Low C

Respirationchange

Kaneda, et.al., 2013. Applied

Soil Ecology, 72: 7-13.

Context dependenceThe effect of soil fauna on N leaching

0

0.5

1

1.5

2

2.5

NTLP NTLA TLP TLA

No fauna Fauna

Total N leaching (mg)

Toyota et al. 2013 Soil Biology and Biochemistry, 60: 105-112.

NO TILL TILLAGE

Including Faunal effects in models

J. Filser , J.J. Jimenez et al., submitted

What about measuring proxies of theiractivities?

Bioturbation ≡ limited tillage+ 50% litter incorporation

Effect of earthworm inoculation on C poolsof the CENTURY model

Source: Lavelle and Spain, Soil Ecology, 2001

Assessing turnover time of biogenic aggregates

NIRS assessment of age and origin of earthworm casts

Comparison of NIR spectra of individual macroaggregateswith a bank of identified spectra

Casts produced in 45 days

Or a simple standard field test of re aggregationof a sieved soil

In fieldconditions

and disaggregation in the absence of faunal and root activities

Disaggregation

Reaggregation

How long does C protection in aggregates last?

Thank you!!

Visit Youtube.com

Patrick Lavelle AmazoniaAmazonia : A happy soil

Globale FatalitéLumbricita perdida

Los Recicladores……