Chapter 3 Flashcards
Species richness varies with
PLOC
Productivity
Latitude
Other physical & biological variables
Climate
Earth’s species may
disappear due to:
(there are 6)
Habitat destruction
Overharvesting (particularly marine species)
Invasive species
Eutrophication
Global Climate Change
Other Human Activities
Naeem et al. (1994) & Tilman and Downing
(1994)
Two studies that paved the way to understand the relationships between
biodiversity and ecosystem functioning.
- see slides
effects of
biodiversity on four important ecosystem
functions: which are
“pinc”
Productivity
Invasibility
Nutrient use and nutrient retention
Community and ecosystem stability
Species richness had a strong, positive effect on
primary productivity
slide 19 not sure how to break up
Increasing species richness increases
biomass production in primary
producers.
question: Does higher species diversity lead to higher ecosystem
productivity?
For at least low-stature plant communities… YES!
A recent meta-analysis of 368 experiments found that manipulated primary
producers in a variety of ecosystems (i.e. terrestrial, freshwater, marine)
resulted in an increase in biomass when high plant species richness occurred.
But, some mathematical modeling has found that although the relationship is
positive,
it occurs at a decelerating rate. (diminishing returns)
Why might productivity increase with species richness?
two mech
Niche complementarity
Species selection
what is niche complementarity
When species differ in the way they
use limited resources.
If each species differs in their
niches, the use of resources within a
community becomes more efficient
and this can leader to higher
productivity.
what is species selection
Species Selection (a.k.a. sampling effect)
May lead to increased productivity with increased species richness if diverse
communities are more likely to contain more productive species that come to
dominate the community.
is the relationship between the extent of ecosystem
functioning and the degree of niche overlap between species npositive or negative ?
negative
Meta analyses
If species exhibit resource partitioning and niche complementarity, then
more diverse communities should use resources more efficiently and the
amount of unused resource in an ecosystem should decline as species
richness increases.
Most data in support of niche complementarity
comes from
terrestrial plants.
nitrogen availability limits
primary productivity.
Nitrogen
in above ground vegetation also correlated
positively with species diversity.
This means N uptake increased with increasing plant diversity.
Dijkstra et al. (2007)
an
increase in plant species richness reduced
that an
increase in plant species richness reduced leaching loss of dissolved inorganic nitrogen.
Cardinale et al. 2011
on polycultures
Found that species-rich polycultures reduced nutrient concentrations (mean
= 48%) more than monocultures
Little evidence that polycultures used resources more efficiently; standing
nutrient concentrations in soil/water were higher in polycultures than the
most efficient monocultures
Do polycultures use resources more efficiently
than the most efficient monocultures?
They Uptake it, but do they use it efficiently?
Simple Answer: it depends on the complexity
homogenous vs heterogeneous
biomass plays a role
heterogeneous streams increased algal richness dramatically reduced the
amount of dissolved nitrogen.
by increasing algal species richness in heterogeneous streams, water quality
was significantly increased due to niche complementarity.
Temporal Stability
Examines species abundance (usually measured in biomass) over time
Diversity had a strong, positive effect on the temporal stability of the total
plant community, but a negative effect on the stability of individual species
abundances.
The idea that increased species diversity leads to ecosystem stability has been
around a long time!
but does it
The answer seems to rest on how we view
stability.
Are more diverse communities more resistant to invasion by exotic species?
Overall, yes, but there are some important unanswered questions.
Elton (1958): “This resistance to newcomers can be observed in established
kinds of vegetation, due to competition for light and soil chemicals and
space.”
Fargione and Tilman (2005) – again using the Cedar Creek plots – found
both biomass and number of invading plants declined as richness of resident
plant community increased.