IV. Productivity, Diversity, and Stability

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IV. Productivity, Diversity, and Stability
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A. Productivity
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A. Productivity 1. Gross Primary Productivity?
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A. Productivity 1. Gross Primary
Productivity Total photosynthetic
productivity CO2 H20 -----gt Glucose O2
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A. Productivity 2. Net Primary Productivity?
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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.
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B. Diversity - Relationships with Productivity
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B. Diversity - Relationships with Productivity
1. Productivity increases diversity
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B. Diversity - Relationships with Productivity
1. Productivity increases diversity
- 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.
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B. Diversity - Relationships with Productivity
1. Productivity increases diversity
- 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.
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B. Diversity - Relationships with Productivity
1. Productivity increases diversity 2.
Diversity increases productivity
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- Sampling Effects More diverse communities
are more likely to contain the most productive
species, and thus raise the total productivity.
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- 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
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Monoculture
Polyculture
They all need the same things at the same
concentrations have to place them far apart to
reduce competition.
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.
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- Positive Interactions More diverse
communities may contain species that benefit
other species, and thus increase the productivity
of the whole community
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Monoculture
Polyculture
without beans
with beans
They all need the same things at the same
concentrations have to place them far apart to
reduce competition.
Nitrogen fixing legumes (beans) nutrify the soil,
increasing the growth of other plants
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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.
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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.
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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
complementarity in natural systems
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- Effects of Genetic Diversity Example
Crutsinger, et al. 2006. Science 313
966-968. Methods - 63 1m2 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.
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- Example Crutsinger, et al. 2006. Science 313
966-968. Results 1 ANPP correlated with number
of genotypes in plot.
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- 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.
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- 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.
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- 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).
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- 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.
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C. Effects on Stability
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C. Effects on Stability 1. Types -
"resistance to change" - "resilience after
change"
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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.
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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).
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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
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Stimulate condensation and precipitation
Volatiles released
Rainforests feed themselves and water themselves.
Decomposition rapid
Absorption rapid
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CUT FOREST DOWN
Select for fire-adapted grasses.... rainforest
doesn't come back....
REDUCE RAINFALL... REDUCE NUTRIENTS INCREASE FIRE
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RAINFOREST (wet, few fires)
"Multiple Stable States"
GRASSLAND (dry, many fires)
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We are dependent on the environment for food and
resources. Ideally, we would like a STABLE,
PRODUCTIVE supply of these resources.... right??
FEAST
FAMINE
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(We don't want "boom and bust", "feast and
famine" scenarios....)
FEAST
FAMINE
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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
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We are playing jenga with our life support
systems...
de Ruiter et al. 2005. Food Web Ecology Playing
Jenga and Beyond Science 30968 - 71
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de Ruiter et al. 2005. Food Web Ecology Playing
Jenga and Beyond Science 30968 - 71