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Rationalising Biodiversity Conservation in Dynamic Ecosystems
Rationalising Biodiversity Conservation
in Dynamic Ecosystems
www.rubicode.net
(RUBICODE)
How trait linkages within and across trophic levels
underlie the response of ecosystem functioning
to environmental change
For further information contact Sandra Lavorel (email:[email protected])
Funded under the European Commission
Sixth Framework Programme
Contract Number: 036890
Rationalising Biodiversity Conservation in Dynamic Ecosystems
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Predicting the response of ecosystem
functioning to environmental change
Chapin et al. Nature 2000
Rationalising Biodiversity Conservation in Dynamic Ecosystems
Key challenges
• Taking into account biotic variability into projections of
ecosystem functioning – at different scales
– Linking biotic responses and changes in ecosystem functioning
• Biodiversity – ecosystem functioning relationships
– Original question: does biodiversity affect ecosystem functioning?
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• 1990 – 2000 : Biodiversity can matter (Loreau et al. 2001, Balvanera et al. 2006)
– Current question: which components of biodiversity affect
ecosystem functioning and through which mechanisms ?
• Functional diversity (Hooper et al. 2005, Diaz et al. 2006)
• Interactions within trophic levels (Chesson et al. 2002)
• Interactions among trophic levels (Thébault & Loreau 2006, Suding et al. 2008)
 New challenge: understanding the role of functional diversity
across trophic levels
Rationalising Biodiversity Conservation in Dynamic Ecosystems
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Presentation outline
• Functional traits and prediction of ecosystem
functioning: some basics
• Going dynamic: linking organisms responses and
ecosystem effects through functional traits (the ‘Holy
Grail’)
• Going multi-trophic : a new framework for the
understanding and projection of ecosystem functions
determined by multiple trophic levels using functional
traits (the next Holy Grail)
• Framework applications and challenges
Rationalising Biodiversity Conservation in Dynamic Ecosystems
Defining functional effect traits
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–
–
–
–
Consume or transform resources
Modify the physical structure of the habitat
Modify the chemistry of the environment
Interact with other organisms (incl. dispersal)
Ecosystem
function
• Relationships between organisms’ characters and key ecosystem
functions
• Traits through which organisms :
Functional diversity*
• In some cases (e.g. microbes) the traits sensu stricto are actually not
known, just the participation to specific processes
 Traits as tools to quantify ecosystem delivery
* Trait value at species or community level; functional divergence
Rationalising Biodiversity Conservation in Dynamic Ecosystems
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Structure-function relationships in plants:
« soft traits »
Function
Soft trait
Fecundity
Dispersal
Establishment
Seed mass
Light interception
Competitive ability
Plant canopy height
Resorption of nutrients;
decomposability of litter
Traits of living leaves
NIRS spectrum
Absorption (nutrients, water)
Carbon fluxes (exsudation…)
Density, diameter
Specific root length
Rationalising Biodiversity Conservation in Dynamic Ecosystems
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Scaling plant function to ecosystems
Enquist et al. 2007 Nature
Rationalising Biodiversity Conservation in Dynamic Ecosystems
Functional traits in other organisms
• Morphological characteristics:
– Body size, feeding apparatus, wings…
• Life history
• Diet and feeding behaviour
• Ecosystem effects
– e.g. microbial activities
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• And…
– Taxonomic groups with specific functions
– Habitat
• Key point: characteristics of individuals that can be related to
mechanisms through which they are affected by environmental
factors and/or they affect ecosystem functioning
Rationalising Biodiversity Conservation in Dynamic Ecosystems
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Functional traits of phytoplankton
Litchmann & Klausmeier Annu. Rev. Ecol. Evol. Syst. 2007
Rationalising Biodiversity Conservation in Dynamic Ecosystems
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Review of evidence for relationships
between traits and ecosystem functioning
247 references, 548 entries for trait-ES relationships across organisms (De Bello et al. 2008)
Abiotic
factors
Ecosystem processes
and services
Functional
diversity
s
s
FD   dij pi p j
i 1 j 1
Weighted mean
n
CWM
trait agg
Trait values
Particular trait values
  pi * traiti
i 1
STAGE 1: Identifying
abiotic & biotic factors
STEP 1
Abiotic factors
Testing the effects of abiotic
factors in ESP
STEP 2
Community-aggregated traits
Testing the effects of communitylevel mean trait values on ES
STEP 3
Trait value distribution
Testing the effects of
trait value distribution on ES
STEP 4
Idiosyncratic species effects
Testing the effects of particular
trait values on ES
STAGE 2:
Finding the best predictive model
STEP 5
Combination of abiotic
and/or diversity factors
Testing the combined effects
of abiotic factors and FD
components on ES
STEP 6
Discontinuous effects
of abiotic and/or diversity
factors
Testing the discontinuous
effects of abiotic factors or
FD components on ES
 What are the relative contributions of abiotic
factors, community mean trait values, trait
value distribution, and individual species
effects on ecosystem functioning?
Available evidence:
which dimensions of functional diversity?
Measures of ecosystem function for
cultures of single species
Relationships between EF and
abundance of growth forms
Relationships between EF and the
diversity of trait values in a community
Relationships between EF and
the mean trait value of the
community
Plant functional traits at community level
The mass-ratio hypothesis
18
Litter decomposability (g/kg/day)
16
CZ-OHR
FR-ERC
FR-HGM
FR-LAU
GE-MNP
GR-LAG
IS-KDE
PT-MER
SC-SUT
SE-BAL
14
12
10
8
6
4
2
0
0
100
200
300
400
500
600
Community-aggregated LDMC
Weighted mean trait value at the community level.
Species effects depend on:
1)
2)
their trait value
their relative contribution to the community
Fortunel et al. 2009 Ecology
Functional complementarity: Considering
the variance rather than the mean
Litter decomposition
Décomposition de la litière
Net effect of diversity
Effet net de la diversité
Nombrerichness
d’espèces
Species
Dissimilitude
fonctionnelle
Functional
dissimilarity
Effects of soil macrofauna on the maintenance of soil fertility :
In the presence of several functional groups (earthworms, isopods,
chilopods) species number has no effect on decomposition.
Functional diversity is the driving variable.
Heemsbergen et al. 2004
Rationalising Biodiversity Conservation in Dynamic Ecosystems
Going dynamic:
Projecting ecosystem functioning
• Determine how the presence / abundance of organisms (with
different effect traits) is modified by environmental change
• Response traits: Traits that determine organisms’ ability to:
• Abiotic: temperature, water, pH, light…
• Nutritional
• Disturbances
Trait value
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– Cope with different environmental conditions
– Colonize newly available habitat
• Dispersal abilities (propagules, individuals)
• Regeneration potential
Environmental variable
The Holy Grail:
Overlapping response and effect traits
Trait value
Ecosystem
function
RESPONSE TRAIT
EFFECT TRAIT
Trait value
Ecosystem
function
Environmental variable
Community
structure and
diversity
Environmental
changes
Response
traits
?
Environmental variable
Lavorel & Garnier Funct. Ecol. 2002
Effect
traits
Ecosystem
functioning
Community
structure and
diversity
Overlapping response / effect traits
Environmental
changes
Response
traits
?
Effect
traits
Ecosystem
functioning
• Can include three types of relationships:
– Response trait = effect trait
• Example: leaf nitrogen content determines response to grassland
management and affects fodder production, maintenance of soil fertility
– Response trait correlated with effect trait through functional
linkage
• Example: defence mechanisms in alternative preys for natural enemies
(effect trait) are correlated with body size (response trait to vegetation
composition)
– Response trait linked with effect trait without functional linkage,
through developmental or phylogenetic constraints
• Example: legumes decrease following grassland management
intensification; legume flowers are those favoured by vulnerable bee
species (long-tongued)
Varying degrees of response-effect overlap
Uncertainty
+
Suding et al. 2008 GCB
Response – effect traits overlap:
Soil water retention through summer in mountain grasslands
Gross et al. New Phytol. 2008
Suding & Goldstein New Phytol. 2008
Beyond plants: multi-trophic control of
ecosystem functioning
de Bello et al. 2008
A new framework to account for the multitrophic control of ecosystem functioning
Pressure
response traits
PR1
Trophic
response traits
TR2
Linkage L1
Linkage L2
Trophic
effect traits
TE1
Functional
effect traits
FE2
Ecosystem function
Trophic level 2
Trophic level 1
Environmental pressure
Framework elements and associated assumptions (1)
Environmental pressure
Pressure
response traits
(PR1)
Trophic level 1
 Assumption 1: Response traits
to environmental pressures
can be identified - pressure
response traits PRi
Trait value *
STEP 1
Environmental variable
* Trait value: single species, or community-level functional diversity metric:
community weighted mean, functional divergence…
Framework elements and associated assumptions (2)
STEP 2
Environmental pressure
Pressure
response traits
(PR1)
Trophic
effect traits
(TE 1)
Trophic level 1
Trophic level 2
Trophic
response traits
(TR2)
 Assumption 2: interactions
between trophic levels can be
related to:
– trophic effect traits: TEi - effects
of organisms within trophic level i
on the adjacent trophic level i+1
– trophic response traits: TRi+1 response of organisms within
trophic level i+1 to organisms
from trophic level i
Evidence for trait-related interactions
Trophic effect traits: plant traits and pollinators
Fenster et al. 2004 Annu. Rev. Ecol. Evol. Syst.
Trophic response traits:
traits of pollinators
associated with floral traits
Stang et al. 2007 Oecologia
Framework elements and associated assumptions (3)
Environmental pressure
Pressure
response traits
(PR1)
Trophic level 2
Trophic
response traits
(TR2)
Trophic
effect traits
(TE 1)
Functional
effect traits
(FE 2)
Trophic level 1
Ecosystem function
 Assumption 3 :
The effects of organisms within
each trophic level i on the
ecosystem function of interest can
be related to particular functional
traits - functional effect traits FEi
Ecosystem
function
STEP 3
Functional diversity*
* Single species, or community-level functional diversity metric: community weighted mean, functional divergence…
Framework elements and associated assumptions (4)
STEP 4
Environmental pressure
Pressure
response traits
(PR1)
Trophic level 2
Trophic
response traits
(TR2)
Linkage L2
Trophic
effect traits
(TE 1)
Linkage L1
Functional
effect traits
(FE 2)
Trophic level 1
Ecosystem function
 Assumption 4 : Within each
trophic level i, linkages Li
among the different types of
response and effect traits can
be identified
Summary of framework features
• Applying the original ‘Holy Grail’
assumptions (1, 3 and 4) to more
than one trophic level to examine
trait overlaps within each of several
trophic levels
• Considering new sets of effect and
response traits associated with
biotic interactions among levels
(assumption 2)
• Extending assumption 4 to
overlaps and associations among
different kinds of response and
effect traits
Influence of grassland management through grazing
on soil N provision via nitrogen transformations
Grazing intensity
Defoliation, trampling,
labile N redistribution
MINERALISERS
PLANTS
PR1a: Stature,
meristem location
PR1b: NO3-/NH4+
assimilation
PR1c = TE1:
leaf N, phenolics, and
root exudates
Urea input
C & energy
supply.
OM quality
NITRIFIERS
TR2: Ability to use
fresh versus
recalcitrant OM
PR3 = TR3:
Sensitivity to high
NH4+/ urea levels
TR2 = TE2 = FE2:
Growth rate
PR3 = TR3 = FE3:
Urease activity
Growth rate
NH4+
supply
FE2:
Specific activity
NO3- / NH4+
NH4+
Maintenance of soil fertility
FE3a: Specific
activity nitifiiers.
FE3b: Ability use
urea as substrate
NO3-
Accounting for more complex trophic networks
Riparian buffer restoration
LEAF SHREDDERS
PLANTS
PR1: suckering,
resistance to root
anoxia, resistance to
shear stress
PR1 = TE1:
Leaf traits: N, size,
toughness, secondary
compounds (lignin),
phenology
Tree size
Branch shedding
FISH
TR2bottom : Feeding
behaviour,
leaf fragmentation
rate
OM quantity
& quality
Wood
provision
TR2bottom = TE2 :
Growth rate,
development time
~ TE2 Phenology
~ TR2top: Body size,
weight per unit length
Fish for angling
Food
supply
Predation
TR3 = FE3 = TE3:
Body size, growth rate
Combining several interaction networks:
Impact of field margin management on multiple ecosystem services
Regular disturbance of field margi ns
PR1 ( Plants)
Flo w eri n g
p eri od
Grow th h a bi t,
Se ed si ze,
L e af N
Se ed si ze,
h ei gh t
T E1
T E1
T E1
TR2 (Invertebr ates)
Bo d y siz e,
Ph en ol o gy
Ove rw in teri n g
si te,
Fe e di ng g ui ld ,
Bo dy siz e
T E2
F E2
Bo dy siz e
T E2
T R3
(Natural enemies)
TR3 ( Birds)
H o st r an ge ,
Ph en ol og y
B ill size ,
Fora gi ng ha bi t,
N es ti ng ha b it
F E3
Biocontrol of
cr op pests
F E3
Regulation of
weed populations
Enjoym ent of
the countryside
Rationalising Biodiversity Conservation in Dynamic Ecosystems
A framework for functional
biodiversity research
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• A heuristic tool to summarise existing knowledge, test hypotheses,
and identify knowledge and data gaps on biotic relationships and
processes that underpin different ecosystem functions
• Flexbility of the framework:
–
–
–
–
–
Number and arrangement of trophic levels
Types of biotic interactions : trophic but not only
Diversity of possible configurations
Using trait syndromes rather than traits
Comparing implementations under different contexts (climate, fertility...)
• Main current limitations :
– Knowledge and data availability for traits in many organisms other than plants
– Quantitative relationships between trait-based metrics (functional diversity) and
ecosystem processes
Rationalising Biodiversity Conservation in Dynamic Ecosystems
www.rubicode.net
Challenges: Analysing complex
dynamics underlying ecosystem functioning
• Do stronger linkages between response and effect traits
lead to more predictable effects of environmental change
on ecosystem services?
• When do feedbacks to environmental pressures or between
trophic levels enhance or reduce predictability of
ecosystem services?
• Do trait effects on ecosystem functioning weaken with
increasing trophic levels, scales, and with multiple driver
interactions?
Rationalising Biodiversity Conservation in Dynamic Ecosystems
www.rubicode.net
Applications
• Quantitative assessments of the effects of environmental
change on ecosystem services provided by biodiversity
• Indication of ecosystem services
• Guiding ecological engineering through the choice of plant
trait assemblages that promote the recovery of a multitrophic community most likely to provide the desired
ecosystem services