Transcript Document

Punch line – species are intimately tied to the cycling and transfer
of Energy and Nutrients through ecosystems.
E.g., #1 – Photosynthetic rates
E.g., #2 – Assimilation rates/ecological efficiencies
E.g., #3 – Impacts of gypsy moths on N-cycling
Will the loss of species richness from communities severely
impact ecosystem processes ?
Ecosystem Processes:
(1) Productivity – higher productivity leads to:
greater number of trophic levels
higher biomass (crop yield)
greater population density
(2) Decomposition
• Magnitude: provides nutrient recycling
• slow and gradual (time-releasing) provides
nutrient release throughout the year
(3) Denitrification
• Removal of harmful levels of
NO3- from the environment
Ecosystem Services:
(1) CO2 sequestration –
reduced greenhouse gas levels; global warming/change
Tree species response to growing at
double the current ambient [CO2]
2
Striped
maple
Ash
Red maple
Yellow birch
1
1
2
3
Years
4
Ecosystem Services:
(2) Pollination – 4500 native bees have been diminishing and
greater reliance is placed on European honeybees… but now
Earthworms….
Ecosystem Services:
(3) Integrated Pest Management and Biocontrol –
(4) Dilution Effect (disease ecology) –
reduced greenhouse gas levels; global warming/change
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+
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Will the loss of species richness form communities severely
impact ecosystem processes ?
redundant
Ecosystem
Process/service
e.g., productivity,
pollination
idiosyncratic
Non-substitutable
Species richness
Redundancy
implies
thatthat
species
partially
compensate
Idiosyncratic
implies
eachcan
unique
combination
of species
for
eachitsother’s
absence,
and
there
is provision
diminishing
Non-substitutable
implies
thatthat
every
species
is unique
and
its to
has
own level
of ecosystem
service
andreturns
is not
species
diversity
in terms
their ability
supply ecosystem
Effects/impacts
cannot
beofsubstituted
bytoothers.
predictable
a priori
services – i.e., not all species are necessary for a fully functional
ecosystem
Why should there be a positive correlation be ecosystem
service and species richness?
Ans #1: Sampling artifact. By chance, a larger group of species
is more likely to contain the MOST productive species than a
small group.
Never exhibits over-yielding, that is, no group of species
can ever outperform a monoculture of the best single species
Productivity
group
A, B, C individually
Implication is plant a monoculture of the most productive crop
Why should there be a positive correlation be ecosystem
service and species richness?
Ans #2: Niche- complementarity – competition theory:
species will evolve to be distinct and thereby reduce
or eliminate competition.
e.g., root
profiles
Because a group of species can more effectively harvest water,
productivity of the group is enhanced over any single species
C
B
Vs.
A
Exhibits over-yielding
Productivity
group
A, B, C individually
Implication is plant a diverse mixture of species – e.g., a stratified
forest
Decomposition of leaf packs in Williamstown, MA
.3
.2
K-value
(decomposition rate) .1
0
-.1
Lonicera maple
beech hemlock
The implication is that a world dominated by Lonicera
releases large amounts of organic matter quickly, but
little remains for the end of the growing season. Therefore,
diversity/richness of stream invertebrates is reduced in
systems with reduced canopy cover
nutrient availability
time
Lonicera maple
beech hemlock
Species diversity/richness and temporal variability
Two lines of thought:
(1) Insurance Hypothesis – rare species are extremely
important under extreme conditions.
(2) Portfolio Effect – More diverse portfolios are less volatile
because, several randomly and independently variable
“items” are less variable than the average item
Services provide by the groups of species include:
stability (the inverse of variability), function during
extreme events (e.g., drought resistance), ability to
resist invasion
Cedar Creek LTER (Univ. MN – David Tilman et al.)
Plant biomass (% cover)
and soil denitrification
rates (less soil nitrate)
increase with species
richness
Plant biomass shows greater
resistance to drought when
species richness is higher
Rare spp response
Rates of species loss from
Amazonian forest fragments.
PNAS 100:14069-14073
100 ha forest fragment
loses 50% of its bird
spp in 15 yrs!!!!
Loss of species is a concerned because the Earth’s biota
performs many valuable functions and services
Valuing species richness and diversity
Aesthetic
Research and Development
Economical
Service (and $$$)