1. IV. Productivity, Diversity, and Stability

2. A. Productivity

3. 1. Gross Primary Productivity?

4. A. Productivity 1. Gross Primary Productivity Total photosynthetic productivity; CO 2 + H 2 0 -----> Glucose + O 2

5. A. Productivity 2. Net Primary Productivity?

6. A. Productivity 2. Net Primary Productivity NPP = GPP - respiration (Plants use some of the energy they absorb; it is not stored as biomass. NPP is only the amount stored as new biomass.

7. B. Diversity - Relationships with Productivity

8. 1. Productivity increases diversity

9. - QUANTITATIVE EFFECT If you have more productivity at the base of a food web, then you can build a longer food chain (adding additional levels AND species)…. And then get keystone effects. B. Diversity - Relationships with Productivity 1. Productivity increases diversity

10. - QUALITATIVE EFFECT An increase in productivity may also occur because more types of food have been added. This may allow for more specialization at the next trophic level - and the coexistence of more species. B. Diversity - Relationships with Productivity 1. Productivity increases diversity

11. B. Diversity - Relationships with Productivity 1. Productivity increases diversity 2. Diversity increases productivity

12. - Sampling Effects More diverse communities are more likely to contain the most productive species, and thus raise the total productivity.

13. - Niche Complementarity More diverse communities are more likely to contain different types of species that use different types of energy... thus more efficiently harvesting the available energy

14. Monoculture They all need the same things at the same concentrations; have to place them far apart to reduce competition. Polyculture Combinations of different plants can be planted at higher density, and they use different "niches" and coexist. Even if abundance of "most productive" species, drops, this loss can be offset.

15. - Positive Interactions More diverse communities may contain species that benefit other species, and thus increase the productivity of the whole community

16. Monoculture They all need the same things at the same concentrations; have to place them far apart to reduce competition. Polyculture Nitrogen fixing legumes (beans) nutrify the soil, increasing the growth of other plants without beans with beans

17. Diversity and Productivity in a Long-Term Grassland Experiment Tilman, et al. 2001. Science 294. 843 - 845 Dotted line is biomass in a monoculture of the most productive species. Higher productivity than this, at higher richness values, means niche complementarity or positive effects must be occurring.

18. Diversity and Productivity in a Long-Term Grassland Experiment Tilman, et al. 2001. Science 294. 843 - 845 Dotted line is biomass in a monoculture of the most productive species. Higher productivity than this, at higher richness values, means niche complementarity or positive effects must be occurring. So, many random assemblages of multiple species have biomass above that of the most abundant monoculture.

19. Diversity and Productivity in a Long-Term Grassland Experiment Tilman, et al. 2001. Science 294. 843 - 845 Dotted line is biomass in a monoculture of the most productive species. Higher productivity than this, at higher richness values, means niche complementarity or positive effects must be occurring. So, many random assemblages of multiple species have biomass above that of the most abundant monoculture. And we might expect greater niche complementa rity in natural systems…

20. - Effects of Genetic Diversity Example Crutsinger, et al. 2006. Science 313: 966-968. Methods: - 63 1m 2 plots, each containing 12 plants of all goldenrod. - The plants in a plot represent either 1, 3, 6, or 12 genotypes, randomly selected from a pool of 21 genotypes.

21. - Example Crutsinger, et al. 2006. Science 313: 966-968. Results: 1: ANPP correlated with number of genotypes in plot.

22. - Example Crutsinger, et al. 2006. Science 313: 966-968. Results: 1: ANPP correlated with number of genotypes in plot. 2: Total insect species diversity, and diversity of herbivores and predators, correlate with ANPP and number of genotypes per plot.

23. - Example Crutsinger, et al. 2006. Science 313: 966-968. Results: 3. The effects were non-additive; there were more arthropods (and herbivores and predators) in 6 and 12 species plots than predicted by adding the richness values of the monocultures.

24. - Example Crutsinger, et al. 2006. Science 313: 966-968. Results: 5: Increase in herbivorous insects due to both MORE food (ANPP - quantitative effect) and DIFFERENT food (niche differentiation - qualitative effect).

25. - Example Crutsinger, et al. 2006. Science 313: 966-968. Results: 6: Increase in predator richness due to increase in herbivore richness, not AMOUNT of food. Some herbivores were only associated with some genotypes.

26. C. Effects on Stability

27. 1. Types - "resistance to change" - "resilience after change"

28. C. Effects on Stability 1. Types 2. Relationships with diversity - more diverse communities are less susceptible to single "types of disturbance" - (a pest, a flood, a drought) - because the many species are unlikely to be sensitive to the same thing.

29. C. Effects on Stability Biodiversity and Ecosystem Functioning: Current Knowledge and Future Challenges. Loreau, et al. 2001. Science 294: 804 - 808 As richness increases, communities become less variable (more stable).

30. C. Stability 1. Types 2. Relationships with diversity - diverse communities may recover more rapidly, too (resilience).... but they may not. Fisheries... yes Rain forest... maybe not

31. Decomposition rapid Absorption rapid Volatiles released Stimulate condensation and precipitation Rainforests feed themselves and water themselves.

32. CUT FOREST DOWN REDUCE RAINFALL... REDUCE NUTRIENTS INCREASE FIRE Select for fire-adapted grasses.... rainforest doesn't come back....

33. RAINFOREST (wet, few fires) GRASSLAND (dry, many fires) "Multiple Stable States"

34. We are dependent on the environment for food and resources. Ideally, we would like a STABLE, PRODUCTIVE supply of these resources.... right?? FEAST FAMINE

35. (We don't want "boom and bust", "feast and famine" scenarios....) FEAST FAMINE

36. We are dependent on the environment for food and resources. Ideally, we would like a STABLE, PRODUCTIVE supply of these resources.... right?? (We don't want "boom and bust", "feast and famine" scenarios....) STABILITY PRODUCTIVITY ?

37. We are playing jenga with our life support systems... de Ruiter et al. 2005. Food Web Ecology: Playing Jenga and Beyond Science 309:68 - 71