Introduction to Ecology
CERC Certificate Program
Columbia University
Session 4 – Ecosystem Ecology
Ecosystem Ecology
•
•
•
•
•
•
•
•
Goals for the day
Why is this field important?
What is a ecosystem?
Trophic Structure
Nutrient cycles and food webs
Ecosystem Processes
Ecosystem engineers
Biomes
Global Changes
Population Growth Exercise
• What did you find?
– Describe the curves – what was happening when?
– When would you get population oscillations in the
Logistic Model?
– Approximate K for humans?
Forensic Entomology
1. Describe forensic entomology and degradative
succession. Why is this an example of it?
2. What can influence the dating of a murder and how
would they? Include at least one from each of the
following more general categories: Timing,
Location, and Chemically-related factors.
3. How to use forensic entomology for the
conservation of animals or of ecosystems?
Succession Definitions
• Chronological
distribution of
organisms within an
area
• The sequence of
species within a
habitat or community
through time
• Shared:
– Time
– Single area
Global Distribution of
Biodiversity
• Greatest in areas where NPP is greatest
– Terrestrial: toward Equator - Why?
– Aquatic: near shore, marine upwellings – Why?
Ecosystem Ecology
•
•
•
•
•
•
•
•
Why is this field important?
What is a ecosystem?
Trophic Structure
Nutrient cycles and food webs
Ecosystem Processes
Ecosystem engineers
Biomes
Global Changes
Uses for Ecosystem Ecology
• Larger Scale phenomena
– Greater geographic range
– More factors
– Ranging from local to global in scope
• Decreased certainty with increasing scales
• Focus of international agencies
Ecosystem Ecology
•
•
•
•
•
•
•
Goals for the day
Why is this field important?
What is a ecosystem?
Trophic Structure
Nutrient cycles and food webs
Ecosystem Processes
Ecosystem engineers
Global Changes
Definition of an Ecosystem
• Properties?
• A system where populations of species group
together into communities and interact with each
other and the abiotic environment.
• The entire biological & physical content of a
biotope
– the smallest geographical unit that can be delimited by
convenient boundaries
=
+
Ecosystem Ecology
•
•
•
•
•
•
•
Goals for the day
Why is this field important?
What is a ecosystem?
Trophic Structure
Nutrient cycles and food webs
Ecosystem Processes
Ecosystem engineers
Global Changes
Trophic Structure
• Definition:
– Feeding relationships among the species
– Within a food web/chain
– Within a single ecosystem
food web
food chain
Trophic Structure
• Influenced by resource availability
– Both biotic and abiotic
• More productive areas tend to have greater trophic
diversity (as well as species diversity – NPP example)
• Connectivity
– Degree and number of associations between species
– What type of species is likely to have the greatest level of
connectivity in the community?
Bottom Up vs. Top Down
Control
• What biotic factor determines organismal
abundance at each trophic level?
Top Down?
Answer:
Depends on
ecosystem &
species
composition
Bottom Up?
Trophic Structure
• Should this be in this lecture?
• Many would argue not
– Why not?
– On what are these folks placing greater emphasis?
food web
food chain
Trophic Structure
• Influenced by resource availability
– Both biotic and abiotic
• More productive areas tend to have greater trophic
diversity (as well as species diversity – NPP example)
• Connectivity
– Degree and number of associations between species
– What type of species is likely to have the greatest level of
connectivity in the community?
Ecosystem Ecology
•
•
•
•
•
•
•
•
Goals for the day
Why is this field important?
What is a ecosystem?
Trophic Structure
Nutrient cycles and food webs
Ecosystem Processes
Ecosystem engineers
Biomes
Global Changes
Nutrient Cycles
• How would nutrient cycles tie in with food
webs?
– Is there anything that is being recycled here?
Stages in Nutrient Cycles
Unassimilated
Biomass
Biomass
Biomass
Biomass
Necromass
Materials Cycled
• Nutrients
–
–
–
–
–
–
Carbon
Hydrogen
Nitrogen
Oxygen
Phosphorus
Sulfur
• Energy?
– Is energy cycled?
Energy
• Does energy
cycle?
• What defines a
cycle?
• Is energy lost /
gained in an
ecosystem?
– How is it lost?
– How is it gained?
Predator
Herbivore
Producers
Energy vs. Nutrients
• Nutrients cycle
– Conservation of material
– A lot of new material does not
generally enter an ecosystem
• Energy flows
– A one-way movement of energy
through an ecosystem
– Energy originates by gathering
solar energy
– Energy lost through growth and
metabolism
Predator
Herbivore
Producers
Ecosystem Ecology
•
•
•
•
•
•
•
•
Goals for the day
Why is this field important?
What is a ecosystem?
Trophic Structure
Nutrient cycles and food webs
Ecosystem Processes
Ecosystem engineers
Biomes
Global Changes
Ecosystem Processes
• Types?
• Examples:
–
–
–
–
–
Water purification
Decomposition
Biomass production
Nutrient cycling
Carbon sequestration
• An emergent property at the
level of ecosystem
Biodiversity and
Ecosystem Processes
•  Biodiversity   ecosystem processes
– Why so?
• Trophic redundancy
– Have multiple species at the same trophic level
– Performing similar ecological roles
– Could lose a few species without major changes
Ecosystem Ecology
•
•
•
•
•
•
•
•
Goals for the day
Why is this field important?
What is a ecosystem?
Trophic Structure
Nutrient cycles and food webs
Ecosystem Processes
Ecosystem engineers
Biomes
Global Changes
Ecosystem Engineers
• Species that create novel ecosystems and habitats
• Examples?
• Anything that significantly modifies the environment
–
–
–
–
–
Pigs in Hawaii
Peccaries in Brazil
Beavers in Northeast
Humans everywhere
Prominent successional species?
Engineering Questions
• Can we substitute species as ecosystem
engineers?
– Are cows good bison substitutes?
– Argument for introducing cattle on Midwest rangeland
• Are these just keystone species?
– What do you think?
Ecosystem Ecology
•
•
•
•
•
•
•
•
Goals for the day
Why is this field important?
What is a ecosystem?
Trophic Structure
Nutrient cycles and food webs
Ecosystem Processes
Ecosystem engineers
Biomes
Global Changes
Biomes
• Definition:
• From Dictionary.com:
– A major regional or global biotic
community
– Chiefly characterized by the dominant
forms of plant life and the prevailing
climate
• Examples:
– Eastern Deciduous Forest, Arctic
Tundra, Grasslands, etc.
Ecological Pyramid
• Trends down pyramid:
– Increase in geographic scale
– From single species to multiple
species
– Increasing number of ecological
factors that may be influential
– Decreasing certainty in results
Population
Community
Ecosystem
Biome
Biosphere
Ecosystem Ecology
•
•
•
•
•
•
•
•
Goals for the day
Why is this field important?
What is a ecosystem?
Trophic Structure
Nutrient cycles and food webs
Ecosystem Processes
Ecosystem engineers
Biomes
Global Changes
Global Changes
• What processes are at work at present in the
planet?
• Examples
–
–
–
–
Global Climate Change
Acid Rain
Spread of Pollution and Toxins
Spread of Biotic Pollution
• How are these occurring?
– What is the generative force behind them?
Global Change Cause
• What is the Generative
Force behind these
changes?
US!
Human Impact
• We have altered nearly all of the Earth that it is
profitable for us to do so
Next Week: The Tour of
Ecology Concludes
• Population ecology
• Community ecology
• Ecosystem ecology
• Conservation Issues
– Next week’s emphasis
– Is there any hope for the
future?