Chapter 3
Ecosystem Ecology
REVERSING THE DEFORESTATION OF
HAITI
•75% < $2.00/day
•1923- 60% forest
•2006 - <2% forest
•What does deforestation do to ecosystem
services?
REVERSING THE DEFORESTATION OF
HAITI
Mango Trees!!!
$70 - $150 of mangos/year!
How does this address the deforestation
problem?
Ecosystem Ecology Examines
Interactions Between the Living and
Non-Living World
• Ecosystem- A particular location on Earth
distinguished by its particular mix of
interacting biotic and abiotic components.
Ecosystem Boundaries
• Biotic and abiotic components provide
boundaries that distinguish one ecosystem
from another.
• Some ecosystems, such as a caves and lakes
have very distinctive boundaries. However,
in most ecosystems it is difficult to
determine where one ecosystems stops and
the next begins.
• Ecosystem boundaries might be defined by
a particular species of interest or
topographic features.
Ecosystem Processes
• Even though it is helpful to distinguish
between two different ecosystems,
ecosystems interact with other ecosystems
by exchanging matter and energy.
Checkpoint…
• What is an ecosystem and what
are its components?
Checkpoint…
• How would you know when you left
one ecosystem and entered
another?
Checkpoint…
How are ecosystem boundaries
different than natural ones?
Energy Flows through
Ecosystems
Photosynthesis and Respiration
• Producers (autotrophs) are able to use the
suns energy to produce usable energy
through the process called photosynthesis.
Let’s demonstrate…
Volunteers please….
Photosynthesis and Respiration
• Cellular respiration is the process by which
other organisms gain energy from eating the
tissues of producers.
Trophic Levels, Food Chains, and Food
Webs
• Consumers (heterotrophs)- obtain energy by
consuming other organisms.
• Primary Consumers (herbivores)- consume
producers.
• Secondary Consumers (carnivores)- obtain their
energy by eating primary consumers.
• Tertiary Consumers (carnivores)- eat secondary
consumers.
• Food Chain- The sequence of consumption from
producers through tertiary consumers.
• Food Web- A more realistic type of food chain
that takes into account the complexity of nature.
Ecosystem Productivity
• Gross primary productivity (GPP)- The total
amount of solar energy that the producers
in an ecosystem capture via photosynthesis
over a given amount of time.
• Net primary productivity (NPP)- The
energy captured (GPP) minus the energy
respired by producers.
GPP = amount you get paid
NPP = amount after taxes
CO2 taken up during photosynthesis =
CO2 taken up in sunlight + CO2 produced in the dark
With this information can determine the GPP of an
ecosystem/day.
Units: kg C/m2/day
(Kilograms of C taken up per m2 per day).
Converting sunlight into chemical energy
is not efficient.
NPP ranges from 25-50% of GPP
Or
0.25% of solar energy striking the plant.
Of the 1% of sun’s energy that is captured
by a producer only 40% is used.
Let’s do the math! 
A forest in North America has a GPP of
2.5 kg C/m2/year.
It loses 1.5 kg C/m2/year to respiration
NPP= 2.5 -1.5 = 1 kg C/m2/year (1.8 lbs C/m2/year)
This means: plants living in 1 m2 of forest will add 1kg
of C to their tissues each year by
growing/reproduction.
NPP= 40% of GPP
ALLOWS US TO COMPARE PRODUCTIVITY AND
CHANGE IN AN ECOSYSTEM!
Energy Transfer Efficiency and Trophic
Pyramids
• Biomass- The energy in an ecosystem is measured in
terms of biomass.
• Standing crop- The amount of biomass/energy
present in an ecosystem at a particular time. (note
different than productivity or rate of energy)
• Ecological efficiency- The proportion of consumed
energy that can be passed from one trophic level to
another.
• Trophic pyramid- The representation of the
distribution of biomass among trophic levels.
Standing Crop
Slow growing forest:
•Low productivity – low
amounts of biomass added
each year
•Standing Crop – biomass
is high
Standing Crop
•Algae – high productivity
due to high growth
rates
--- standing crop is l
ow due to primary
consumers.
Ecological Efficiency
• 10% rule
• Only about 10% of the available biomass at
each trophic level can be converted into
energy at the next level.
• REPRESENTED BY THE TROPHIC
PYRAMID
Suppose all humans
decided to become
vegetarians….
• 1 acre of cropland = 1,000 kg soybeans
• 10x more food available if eaten raw reather
than feeding to beef to eat meat.
• 1kg of soybeans = 2.5x calories as beef
• 1 acre would produce 25x more caloires.
MORE LAND REQUIRED TO BE
SECONDARY CONSUMER!
Checkpoint…
• Why is photosynthesis an
important process?
Checkpoint…
• What determines the productivity of
an ecosystem?
Checkpoint…
• How efficiently is energy
transferred between trophic levels
in an ecosystem?
STOP HERE
• Make a list of what you ate today for lunch and
where it came from (animals, plants etc.)
• Make a trophic pyramid and place all
organisms in each level.
• At which level did you get most of your
energy?
Matter cycles through the biosphere
• Biosphere- The combination of all ecosystems on
Earth.
• Biogeochemical cycles- The movement of matter
within and between ecosystems involving biological,
geologic and chemical processes.
I
What type of system is this?
The Hydrologic Cycle
• The movement of water through the
biosphere.
The Hydrologic Cycle
• Transpiration- The process where plants
release water from their leaves into the
atmosphere.
• Evapotranspiration- The combined amount
of evaporation and transpiration. (often used
to measure water through an ecosystem)
• Runoff- When water moves across the land
surface into streams and rivers, eventually
reaching the ocean.
Human Activities and
Hydrologic Cycle
• Havesting Trees
• Paving Roads
• Diverting Water
The Carbon Cycle
Carbon Cycle
• Photosynthesis (plants)
• Respiration (animals)
• Exchange (atmosphere and ocean)
• Sedimentation and burial
• Extraction (recent phenomenon)
• Combustion (fossil fuels/timber)
• Faster processes involve living organisms.
Carbon Cycle
• Producers – water
• Consumers – food
• Decomposers – dead organisms
• During Decomposition elements become
available to producers again.
The Nitrogen Cycle
Nitrogen Cycle Step 1
• Only a few organisms can conver Nigrogen into ammonia.
By NITROGEN FIXATION
• Cyanobacteria, bacteria in legume roots
• Enzymes break nitrogen bond and add hydrogen to form
ammonia and ammonium in the soil.
• Bacteria excrete ammonium into plant roots and plant
gives bacteria sugars.
• LIGHTENING/COMBUSTION – Nitrogen to nitrate
Step 2 - Assimilation
Nitrogen assimilated into tissues
Step 3 Ammonification
• Decomposers use nitrogen wastes and
dead bodies as food and excrete
ammonium
Step 4 - Nitrification
• Bacteria convert ammonium into nitrite and
then nitrate (minor importance but can be
used by producers)
Step 5 - Denitrification
• Nitrate is transported through soil (leaching)
• Bacteria in waterloggged soil convert nitrate
into nitrous oxide and nitrogen gas and put
back into the atmosphere.
The Phosphorus Cycle
Ecosystems respond to disturbance
• Disturbance- An event caused by physical,
chemical or biological agents that results in
changes in population size or community
composition.
Watershed Studies
• Watershed- All of the land in a given
landscape that drains into a particular
stream, river, lake or wetland.
Resistance versus Resilience
• Resistance- A measure of how much a disturbance
can affect its flows of energy and matter.
• Resilience- The rate at which an ecosystem returns
to its original state after a disturbance.
• Restoration ecology- A new scientific discipline
that is interested in restoring damaged ecosystems.
The Intermediate Disturbance Hypothesis
• The intermediate disturbance hypothesisstates that ecosystems experiencing
intermediate levels of disturbance are more
diverse than those with high or low
disturbance levels.
Ecosystems Provide Valuable
Services
Instrumental vs Intrinsic
Instrumental Values of Ecosystems
• Provisions- Goods that humans can use directly.
• Regulating services- The service provided by natural
systems that helps regulate environmental conditions.
• Support systems- The support services that natural
ecosystems provide such as pollination, natural filters
and pest control.
• Resilience- Resilience of an ecosystem ensures that it
will continue to provide benefits to humans. This
greatly depends on species diversity.
• Cultural services- Ecosystems provide cultural or
aesthetic benefits to many people.