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?
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