1. Diversity and productivity The relationship between biodiversity and productivity has four different aspects How does productivity depend on biodiversity (local scale)? How does temporal variability influence productivity (local scale)? How does biodiversity depend on productivity (regional scale)? How does productivity influence temporal variability (regional scale)?

2. Darwin’s Wormestones How does productivity and variability depend on biodiversity (local scale)? P = f(S)   (P)=g(S)

3. Species and populations Biomass, Productivity, Enrgy turnover How does non-equilibrium population variability at the species level influence aggregate variables at the community level?

4. The portfolio effect YearABCDEFSum 1791724165623446896607 2734801833170566845658 3588880486232826251544 42987268556682625403 5129549590782775622574 65756562740655103455 710426557648692292437 8703706387649744128553 9711729429199397728532 109472949713722780509 118342447582537625472 1235753071221771764453 1371296131223659237419 14970889328477376906657 15522464889973579424642 CV0.480.430.70.660.450.520.16 The coefficient of variation CV of a sum of random variates is smaller than single CVs.

5. For 1 species: If no species interactions cov (i,j) = 0: The portfolio effect For S species: The variability of aggregate variables should decrese with increasing species diversity The majority of species has 1.5 < z < 2.5 Assume we have S species that fluctuate independently in time. Assume further an aggegate variable that is the sum of single species values (f. i. biomass, total assimilation, energy use) The decrease in variability follows a power function David Tilman (1949-

6. 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. y = 12.8Ln(x) + 11.5 R 2 = 0.96 0 10 20 30 40 50 60 01020 Number of species Total plant cover (%) y = 28.6Ln(x) - 10.7 R 2 = 0.77 0 20 40 60 80 100 01020 Number of species Total plant cover (%) LTER – Long term ecological research at Cedar Creek, Minnesota

8. Grassland aboveground biomass depends on several factors among which locality, diversity and functional diversity are of major importance. Results of the BIODEPTH experiment Grassland productivity declines as the number of functional groups decreases. 0 200 400 600 800 0123 Number of functional groups Aboveground biomass [g m -2 ] S = 8 S = 11 S = 4

9. Biodiversity and bacterial activity (Bell et al. 2005) 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 28 days experimental time Day 0-7 Day 14-28 Day 7-14

10. Ecosystem functioning and dispersal Eelgras – crustacean grazer marine mesocosms systems (France and Duffy 2006) -Dispersal increases the variability of ecosystem services -Species richness at low dispersal decreases the variablity of ecosystem services -Species richness at high dispersal increases the variablity of ecosystem services -Habitat fragmentation and decrease in species richness act synergistically on ecosystem stability

11. 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 Bacterial activity increases with foodweb complexity Stability decreases with dispersal among patches Habitat fragmentation and species richness act synergistically and decrease stability

12. Today’s reading Biodiversity and ecoystem functioning: http://biology.mcgill.ca/faculty/loreau/pdfs/loreauetalscience.pdf http://biology.mcgill.ca/faculty/loreau/pdfs/loreauetalscience.pdf The Portfolio effect: www.ird.fr/ur060/resultats/2002_LhommeWinkel_TPB.pdf www.ird.fr/ur060/resultats/2002_LhommeWinkel_TPB.pdf