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Biodiversity and ecosystem
functioning (BEF) in grasslands
From patterns to mechanisms
Prof. Dr. Michael Scherer-Lorenzen
Geobotany – Experimental Vegetation Science
“Does biodiversity matter?”
 Ecosystems greatly differ in biological richness,
but have a similar basic set of energy- and
matter-fluxes

Cryptoendolithic ecosystem in Antarctica
After Friedmann 1982 Science, and Woodward 1993 Springer
“Does biodiversity matter?”
 Ecosystems greatly differ in biological richness,
but have a similar basic set of energy- and
matter-fluxes

Tropical rainforest
Nutrient input with rain
N-fixation
C-assimilation
Biogeochemical
cycling
Leaching
Nutrient input
After Schulze et al. 2002 Spektrum
After Schultz 2000 Ulmer
“Does biodiversity matter?”
 Global loss of biodiversity: any consequences
for ecosystem functioning?
Millenium Ecosystem Assessment
Core Projects
 Understanding relationships
between biodiversity and
ecosystem functioning and
services

Focus 1: Biodiversity and
ecosystem functioning

Focus 2: Linking ecosystem
functioning to the provision of
services

Focus 3: Human responses to
changes in ecosystem services
Drivers of biodiversity
Biotic community
(biodiversity)
•
•
•
•
Composition
Richness
Evenness
Species interactions
Abiotic controls
• Resource availability
• Modulators (T, pH)
• Disturbance regime
S = f(B, A, ε)
S:
B:
A:
ε:
biodiversity, species richness
biotic interactions
abiotic conditions
error term (e.g. chance events)
Drivers of biodiversity
Global changes
•
•
•
•
Biogeochemical cycles (C, N, P, organics)
Land use (type, intensity)
Climate
Species invasions
Biotic community
(biodiversity)
•
•
•
•
Composition
Richness
Evenness
Species interactions
Abiotic controls
• Resource availability
• Modulators (T, pH)
• Disturbance regime
Walther et al. 2002 Nature
Ecosystem functioning
Global changes
•
•
•
•
Biogeochemical cycles (C, N, P, organics)
Land use (type, intensity)
Climate
Species invasions
Biotic community
(biodiversity)
•
•
•
•
Composition
Richness
Evenness
Species interactions
Ecosystem properties
and processes
Abiotic controls
• Resource availability
• Modulators (T, pH)
• Disturbance regime
Chapin et al. 2002
Ecosystem services
Global changes
•
•
•
•
Biogeochemical cycles (C, N, P, organics)
Land use (type, intensity)
Climate
Species invasions
Biotic community
(biodiversity)
•
•
•
•
Composition
Richness
Evenness
Species interactions
Abiotic controls
• Resource availability
• Modulators (T, pH)
• Disturbance regime
Ecosystem goods
and services
Ecosystem properties
and processes
Ecosystem services
Global changes
•
•
•
•
Biogeochemical cycles (C, N, P, organics)
Land use (type, intensity)
Climate
Species invasions
Biotic community
(biodiversity)
•
•
•
•
Composition
Richness
Evenness
Species interactions
Abiotic controls
• Resource availability
• Modulators (T, pH)
• Disturbance regime
Human activities
Ecosystem goods
and services
Ecosystem properties
and processes
Biodiversity and ecosystem functioning
Global changes
•
•
•
•
Biogeochemical cycles (C, N, P, organics)
Land use (type intensity
Climate
Species invasions
Biotic community
(biodiversity)
•
•
•
•
Composition
Richness
Evenness
Species interactions
Human activities
Ecosystem goods
and services
Species
traits
Ecosystem properties
and processes
Abiotic controls
• Resource availability
• Modulators (T, pH)
• Disturbance regime
After Hooper et al. 2005 Ecol Monogr
Biodiversity as the predictive variable
 Biodiversity as a driver of ecosystem processes
 Ecosystem functioning: a function of biodiversity
 Species traits represent the functional link
Biotic community
(biodiversity)
•
•
•
•
Composition
Richness
Evenness
Species interactions
Abiotic controls
• Resource availability
• Modulators (T, pH)
• Disturbance regime
F = f(S, A, ε)
Species
traits
Ecosystem properties
and processes
1st Exercise
 How would you study the effects of biodiversity
(e.g. plant species richness) on ecosystem
functioning (e.g. biomass production)?
Biotic community
(biodiversity)
•
•
•
•


Composition
Richness
Evenness
Species interactions
Ecosystem properties
and processes
Groups of 3 persons (one from each continent)
5 min discussion, short presentation
BEF-Approaches (suggestions by
paerticipants)
 Experiment with different species richness levels
in plots (1, 2, 4 species etc.), then measure CO2,
harvest)
 Removal Experiment: „delete“ certain species or
functional groups; then measure biomass …
 Comparative study (define system boundaries,
select plots, determine SR and FG (incl.
animals), measure BM; long-term perspective
 Modelling
Approaches
 Observational/comparative studies between sites
vs.
Soil?
Climate?
Age?
History?
Management?
}
Documentation: 
Causality: 
Experimental
approaches are
needed
Synthetic community approach
 Randomly allocate diversity treatments to plots
within one site, keeping environmental conditions
as constant as possible
 Sowing or planting of new communities, creating
a gradient of plant diversity
 Within-habitat effects of diversity can be detected
 Necessary, since without experimental
manipulation we are not able to understand why
things are the way they are
Ecotron
 Environmentally controlled, simplified
communities of terrestrial plants, animals
and microbes as models of the real world
Naeem et al. 1994 Nature
Cedar Creek
 Large field experiments with more than 390 plots,
manipulating species richness, functional group
richness and composition
BIODEPTH
 BIODiversity and Ecological Processes in
Terrestrial Herbaceous ecosystems

480 plots of 4m2
The Jena Experiment
 The role of biodiversity for element cycling and
trophic interactions


90 large plots
(400m²)
404 small plots
(12m²)
© A. Weigelt
The Jena Experiment
x
Management experiment:
• Split-plot design Mowing/Fertilization:
randomized, levels: 2x/100; 4x/100;
4x/200;
• Climate change experiment: roofs
over half of the management plot areas
for 6 weeks prior to second harvest
Island (1.6x4m)
Roscher
Insect refuge 1xMowing
Pla lan sampling
Manag. (1.6x4m)
100kg + 4xMowing
y
TPZ (2x4m)
Climate change control
TP10 (0.85x4m)
Manag. (1.6x4m)
Core area:
• Cover estimates TP10: 3x3m
• Climate change control with roof and
roof control with water addition
• Area for moving window of a 2m² for
plant sampling of Barnard
200kg + 4xMowing
Manag. (1.6x4m)
100kg + 2xMowing
Phytometers (all plots)
•
TP10/TP12/TP1 (planted 2006)
New 2008/2009:
bold line: weeded area TPZ since July
2008
TP 10
(3x3m):
Barnard (3x5.5m)
Cover estimates
plant sampling 2009
CR
Hydrology
• Lol per now a 1m² randomized area
• CR: weeding area Abovergr. Prod.
• Hydrology: new sensors in 2, 4, 8 SR
in Block 1+2
• additional sensors installed at central
pole in Block 2 (Barnard)
red corner
TP1
Interaction with management and climate
change
 Additional experiment



Diversity gradient
Management intensity
Summer drought
Charles Darwin…was the first
 In “On the Origin of Species” (1872, p. 113):



“ It has been experimentally proved that if a plot of
ground be sown with one species of grass, and a
similar plot be sown with several distinct genera of
grasses, a greater number of plants and a greater
weight of dry herbage can thus be raised.”
Set up by George Sinclair, located in Woburn Abbey
242 plots
Hector & Hooper 2002 Science
2nd Exercise
 How could the relationship between plant species
Biomass production
richness and biomass production look like?
Species richness
2nd Exercise
 How could the relationship between plant species
Biomass production
richness and biomass production look like?
Species richness
2nd Exercise
 How could the relationship between plant species
Biomass production
richness and biomass production look like?
Species richness
2nd Exercise
 How could the relationship between plant species
Biomass production
richness and biomass production look like?
Species richness
2nd Exercise
 How could the relationship between plant species
Biomass production
richness and biomass production look like?
Species richness


Groups of 3 persons (one from each continent)
5 min discussion, short presentation
Biomass production
 Consistent positive (log-)linear relationship
between plant diversity and biomass production
Aboveground biomass (g/m2)
1400
1200
1000
800
600
400
200
0
0
5
10
15
20
25
30
35
Species diversity
After Hector et al. 1999 Science
Tilman et al. 2001 Science
Biomass production
 Pattern changes depending on site conditions
and on annual climatic variability
 Relationship gets stronger with time
Site:
Div (log):
Site x Div
P=0.002
P<0.001
P=0.466
Year:
Year x Site
Year x Div
P<0.001
P<0.001
P= 0.002
Spehn et al. 2005 Ecol Monogr
Biomass production: Jena Experiment
 Positive effects of both species richness and
functional group richness
Marquard et al. 2009 Ecology
Drought and management experiment
600
500
M2F100
M2F0
2009 roofed
2009 unroofed
2008 roofed
2008 unroofed
400
Biomasseproduktion [g/m²]
300
200
100
0
1
2
4
8
16
60
200 M4F100
M4F200
150
2009
Species richness
100
50
0
Drought
1
2
4
8
Artenzahl
Differences due to management
16
60
1
2
4
8
16
60
Soil C sequestration
 Increase in soil C pool with diversity
Steinbeiss et al. 2009 Ecology
Litter decomposition
 Increase in litter decomposition rates

driven by microclimate and litter quality: functional
diversity matters!
Scherer-Lorenzen et al. 2008 Functional Ecology
Soil N pools
 Increasing species richness (or number of
functional groups) decrease soil available N
pools
with legumes
without legumes
Sweden
NO3- - N [kg/ha]
6
5
4
3
2
1
0
1
2
3
No. of functional groups
Spehn et al. 2005 Ecol Monogr
Palmborg et al. 2005 Oikos
Species richness
Roscher et al. 2008 J Ecol
Nitrate leaching
 Diversity strongly reduces leaching losses in
Leaching loss [kg NO3--N ha-1 a-1]
communities containing N-fixers
without legumes
with legumes
bare ground plots
reference plots
total mean
Bayreuth, 1998
120
b
a
80
120
80
Legumes
Div (log)
Leg x Div
Mixtures
***
*
*
***
Funct group *
40
40
0
0
0
1
2
4
8
16
Plant species richness
(log2 scale)
25
1
2
3
Functional
group richness
Scherer-Lorenzen et al. 2003 Ecology
Multifunctionality
Aboveground
Belowground
Biodiversity
Allen et al. 2003 in pep.
Multifunctionality


Different
species
influence
different
processes
Many species
required for
multiple
processes
Hector & Bagchi 2007 Nature
Underlying mechanisms
 Sampling and selection effects



Only one or a few species with specific traits might
have large effects, increasing diversity enhances the
likelihood that those species are present
If these species gain dominance, productivity and
resource use should rise with diversity
Species interactions that lead to competitive exclusion
Tilman 1999 Ecology
Underlying mechanisms
 Positive species interactions
among species

Complementarity in resource use
and facilitation (“complementarity
effect”, Loreau & Hector 2001)

Overyielding: production in
mixture is higher than expected
based on monoculture yields
Species interactions that lead to
species coexistence (diversity
promoting mechanisms)

Tilman 1999 Ecology
Niche differentiation
 Spatial heterogeneity: vertical

Differences in above- or belowground architecture:
canopy/root stratification
Ellenberg 1986
Niche axis 2
Niche axis 2
Niche axis 2
From niche differentiation to
complementarity
Niche axis 1
Niche axis 1
Niche axis 1
43
Niche axis 2
Niche axis 2
From niche differentiation to
complementarity
Niche axis 1
Resource use
Resource use
Niche axis 1
Mono
Mix
Mono
Mix
44
Facilitation
 Fertilization effect through N-fixing legumes

But not on all sites
Hector et al 2007 Functional Ecology
a: Germany
b: Portugal
c: Switzerland
d: Greece
e: Ireland
f: Sweden
g: UK (Sheffield)
h: UK (Silwood)
Detecting facilitation
 Additional N source through fixation
Spehn et al. 2002 Oikos
Detecting facilitation
 Transfer of fixed N to neighbouring plants
with legumes
without legumes
Spehn et al. 2002 Oikos
Detection of complementarity
 Comparison of growth in
monoculture and in
mixture

Many species have higher
biomass in mixture than
expected on their
monoculture yield

Relative yield totals higher
than 1: overyielding
Complementarity effects
greater than selection
Roscher et al. 2005 Ecol Lett; Fargione et al. 2007 Proc Roy Soc B
effects

48
Detecting mechanisms of complementarity
 Canopy stratification

Higher space filling (2D and 3D)
LAI, > 0.05m [m2 m-2]
9
May 1997
June 1998
7
5
3
12 4
8
16
Species richness
Scherer-Lorenzen 1999 Bay Forum Ökol
Spehn et al. 2005 Ecol Monographs
Detecting mechanisms of complementarity

Below-ground complementarity for N can occur through the use
of different chemical forms (NO3+, NH4- or organic N), or through
differences in spatial or temporal activity of resource uptake.
- 12cm
(Levins‘ normalized B)
- 3cm
Niche breadth
1.0
0.9
0.8
0.7
0.6
0.5
0.4
1
3
6
Species richness
15NO
NO33--, 15NH44++ , 13
Glycin
C-15N-Glycin
Von Felten et al. 2009 Ecology
Applied aspects: forage yield and quality
 Observational studies
Yield
Forage quality
 Productivity decreases with diversity
 Forage quality decreases as well
 Forage quality is dependent on species composition
Species richness
Management Experiment
 Diversity gradient (1, 2, 4, 8, 16, 60 species),
crossed with management intensity gradient
Management Experiment
Management Experiment
 Diversity effects on biomass production stronger
than intensification!
M1 F0
M2 F0
M2 F100
M4 F100
M4 F200
Biomass (g m-2 a-1)
1200
1000
800
600
Div.
Bew.
DxB
440
400
315
200
0
1
2
4
8
16 60 R
Species richness(log)
Weigelt et al. 2009. Biogeosciences
P<0.001
P<0.001
P=0.343
Management Experiment
 Strong legume effects
 Fertilization useless in plots with legumes
Aboveground biomass (g*m-2*y-1]
No fertilizer
Fertilizer
1000
Leg.
LxM
800
600
400
200
0
Fertilizer: 0
Mowing: 1
0
2
100
2
100
4
Management gradient
After Weigelt et al. 2009. Biogeosciences
200
4
P<0.001
P<0.001
Management Experiment
 Forage quality rather independent of diversity
 “Forage quality yield” increases with diversity
Scherer-Lorenzen et al. in prep.
Applied aspects:
Bioenergy
 Potential of low input - high
diversity (LIHD) grasslands
for biofuel production?
Bioenergy
Tilman et al. 2006. Science
Bioenergy
Tilman et al. 2006. Science
Bioenergy
 Increasing biomass energy yield
 High soil C-sequestration






No monoculture
Low management intensity
Higher GHG mitigation potential: C-negative
Habitat function
Possible on degraded lands
no displacement of food production, nor conflicts
with nature conservation
 High potential for multifunctional grasslands
Conclusions
 High-diversity communities have many „positive“
effects on ecosystem functioning and services

They have stronger complementarity effects, and exploit
more resources by intercepting more light, taking up
more nitrogen, and utilize more 2- and 3-dimensional
space
 Functional biodiversity research should rely on a
variety of approaches, with experimental
manipulations being essential to detect
mechanisms
Future challenges
 Mechanistic understanding of diversity effects

Plant traits and their variability, based on ecophysiology
 Diversity effects in other and/or more complex
communities

Natural grasslands, forests, marine systems…
 Manipulation of other aspects of biodiversity

Genetic, structural and functional diversity
 Asking the “so what?” questions


Biodiversity and ecosystem services (hydrology, erosion)
Impacts of global change
Thank you!
63
Definitions
 Biodiversity



The variety of life
Number, abundance and composition of genotypes,
populations, species, functional types and landscape
units in a given system
α-, β-, γ-diversity
 Functional groups (types, guilds)

Sets of organisms that affect ecosystem properties or
processes in a similar way (functional effect groups);
and/or that respond to changes in the environment
(functional response groups) in a similar way
Definitions
 Ecosystem functioning

Sizes of compartements (e.g. N-pools) and rates of
processes (e.g. N-fluxes); properties of ecosystems
 Ecosystem services

Benefits people obtain from ecosystems, including
provisioning services (e.g. food, fiber, genetic
resources), regulating services (e.g. erosion control,
climate regulation, pollination), cultural services (e.g.
spiritual and religious, recreational, educational), and
supporting services (e.g. soil formation, primary
production, nutrient cycling) [Millenium Ecosystem
Assessment]