Function and diversity
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Function and diversity. The Portfoilio effect Statistical averaging. David Tilman (1949-. Michel Loreau. If species act indepe n dent the coefficient of variation of aggregate ecosystem properties is expected to decrease to the root of species richness.

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Function and diversity

Function and diversity

The Portfoilio effect

Statistical averaging

David Tilman (1949-

Michel Loreau

If species act independent the coefficient of variation of aggregate ecosystem properties is expected to decrease to the root of species richness.

Aggregate properties are particularly:

Biomass

Total abundance

Productivity

Assimilation


Function and diversity

The law of the minimum and ecosystem functioning

Average performance withoutlimitingeffects

Performance with limitingeffects

Species at minimum limit the functioning of ecosystem properties

Ecosystem functioning increases non-lineary with species richness.

Point of fast change

Point of fast change

This model works if species form functional guilds whose members have equivalent properties.


Function and diversity

The law of the minimum

Limiting factors:

Light

Water

Space

Nutrients

Justus von Liebig (1803-1873)

Water is the limiting factor for photosynthetic rates with respect to temperature

Euryoecious organisms tolerate a wider range of habitat conditions.

Stenoecious organisms have limited tolerance.

Photosynthetic activity

Precipitation

Temperature


Function and diversity

60

100

50

80

40

60

Total plant cover (%)

Total plant cover (%)

30

40

20

y = 12.8Ln(x) + 11.5

20

y = 28.6Ln(x) - 10.7

10

2

R

= 0.96

2

R

= 0.77

0

0

0

10

20

0

10

20

Number of species

Number of species

LTER – Long term ecologicalresearchatCedarCreek, Minnesota

Variance and covariance of native savannah plants at Cedar Creek in relation to species diversity.

147 experimental plots at Cedar Creek in Minnesota

120 samples from undisturbed native Minnesota grasslands.

Tilman 1999, Ecology 80: 1455-1474


Function and diversity

Results of the BIODEPTH experiment

Grassland aboveground biomass depends on several factors among whichlocality, diversity and functional diversity are of major importance.

Hector et al. 1999, Science 286, 1123-1127

Grassland productivity declines as the number of functional groups decreases.


Function and diversity

Biodiversity and bacterial activity

Day 0-7

Day 7-14

28 days experimental time

Day 14-28

Bell et al. 2005, Nature 436: 1157-1160

Bacterial species richness influences respiration of soils from beech stands.

Respiration is not a linear function of bacterial richness

This points to the existence of redundant species


Function and diversity

  • The current state of art:

  • Ecosystem functioning depends not such much on species richness but on richness of functional groups (ecologigal guilds)

  • Productivity increases with plant functional group richness

  • Stability increases with plant functional group richness

  • Drought restistance increase with plant functional group richness

  • Bacterial species richness promotes efficiency of bacterial services like breakdown of pollutants

  • Decomposition increases with eukaryotic species richness

  • Total bacterial activity increases with bacterial foodweb complexity

  • Stability decreases with dispersal among patches

  • Habitat fragmentation and species richness act synergistically and decrease stability


Function and diversity

How do diversity and stability depend on productivity?

Speciesrichnesspeaksoftenatintermediateproductivity


Function and diversity

250

Palearctic birds

200

150

S

100

50

0

0

500

1000

1500

Evapotranspiration

250

Palearctic butterflies

200

150

S

100

50

0

0

500

1000

1500

Evapotranspiration

Evapotranspiration is the sum of evaporation and transpiration, hence the total amount of water going from living organismas and the soil into the atmosphere.

It is a measure of total energy input.

Hawkins et al. 2003, Ecology 84: 3105-3117

Species richness often peaks at intermediate degrees of evapotransiration.


Function and diversity

Hawkins et al. 2003, Ecology 84: 3105-3117

Bird species numbers are correlated with annual evapotranspiration and temperature.


Function and diversity

The influence of productivity on the species richness of plants

Meta-analysis found very variable patterns of the productivity species richness relationship at local scales.

Above the local scale plant species richness increases with productivity.

Gillman, Wright, 2006, Ecology 87: 1234-1243


Function and diversity

Patterns of fish species richness in China’s lakes

Zhao et al. 2006, Gl. Ecol. Biogeogr.


Function and diversity

140

140

2

2

R

= 0.75

R

= 0.34

120

120

100

100

80

80

S

S

60

60

40

40

20

20

0

0

1

10

100

1000

10000

1

10

100

1000

Altitude [m]

Maximum depth [m]

140

140

120

120

100

100

80

80

S

S

60

60

40

40

20

20

0

0

0.001

0.1

10

1000

0.1

10

1000

100000

8

3

2

Lake volume [10

m

]

Lake area [km

]

Fish speciesrichnessscalessignificantly with altitude and maximum depth of a lake

Lake volumeis of minor importance


Function and diversity

1000

1000

2

2

R

= 0.43

R

= 0.57

100

100

S

S

10

10

1

1

-10

0

10

20

30

0

500

1000

1500

Annual potential

Mean annual temperature

evapotranspiration [mm]

1000

1000

2

2

R

= 0.53

R

= 0.40

100

100

S

S

10

10

1

1

0

500

1000

0

500

1000

1500

2000

Annual actual

Annual precipitation [mm]

evapotranspiration [mm]

Main determinants of fish species richness were annual PET, altitude, and lake area.


Function and diversity

Productivity and stability

Are tropical populations more stable than populations in temperate or arctic regions?

There is no general latitudinal trend in population variability

Vazquez, Stevens, 2004, Am. Nat 164: E1-E19


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