Introduction to Ecology

Introduction to EcologyIntroduction to Ecology

CERC Certificate ProgramColumbia University

Session 4 – Ecosystem Ecology

Ecosystem EcologyEcosystem Ecology

• Why is this field important?• What is a ecosystem?• Trophic Structure • Nutrient cycles and food webs • Ecosystem Processes • Ecosystem engineers• Biomes • Global Changes

Goals for the day

But Before That….

But Before That….

Let’s Discuss the Population Growth

Let’s Discuss the Population Growth

and Forensic Entomology Exercises

and Forensic Entomology Exercises

Population Growth Population Growth ExerciseExercise

• 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 EntomologyForensic Entomology1. 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 DefinitionsSuccession 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 Global Distribution of BiodiversityBiodiversity

• Greatest in areas where NPP is greatest– Terrestrial: toward Equator - Why?– Aquatic: near shore, marine upwellings – Why?


• 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 Uses for Ecosystem EcologyEcology

• Larger Scale phenomena– Greater geographic range– More factors – Ranging from local to global in scope

• Decreased certainty with increasing scales

• Focus of international agencies


• Why is this field important?• What is a ecosystem?• Trophic Structure • Nutrient cycles and food webs • Ecosystem Processes • Ecosystem engineers • Global Changes

Goals for the day

Definition of an Definition of an EcosystemEcosystem

• 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= +


• Why is this field important?• What is a ecosystem?• Trophic Structure • Nutrient cycles and food webs • Ecosystem Processes • Ecosystem engineers • Global Changes

Goals for the day

Trophic StructureTrophic Structure

• Definition:– Feeding relationships among the

species – Within a food web/chain– Within a single ecosystem

food chain

food web

Trophic StructureTrophic 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 Bottom Up vs. Top Down ControlDown Control

• What biotic factor determines organismal abundance at each trophic level?

Top Down?

Bottom Up?

Answer: Depends on ecosystem & species composition

Trophic StructureTrophic Structure• Should this be in this lecture?• Many would argue not

– Why not?– On what are these folks placing greater

emphasis?

food chain

food web

Trophic StructureTrophic 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?



Goals for the day

Nutrient CyclesNutrient Cycles• How would nutrient cycles tie in with

food webs?– Is there anything that is being recycled

here?

Stages in Nutrient Stages in Nutrient CyclesCycles

Unassimilated

Biomass

Biomass

Biomass

Biomass

Necromass

Materials CycledMaterials Cycled• Nutrients

– Carbon– Hydrogen– Nitrogen– Oxygen– Phosphorus– Sulfur

• Energy?– Is energy cycled?

EnergyEnergy• 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. NutrientsEnergy 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



Goals for the day

Ecosystem ProcessesEcosystem Processes• Types?• Examples:

– Water purification– Decomposition– Biomass production– Nutrient cycling– Carbon sequestration

• An emergent property at the level of ecosystem

Biodiversity and Biodiversity and Ecosystem Processes 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



Goals for the day

Ecosystem EngineersEcosystem 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 QuestionsEngineering 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?



Goals for the day

BiomesBiomes• 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 PyramidEcological 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

Biome

Biosphere

Population

Community

Ecosystem

Where do Biomes

Fit?



Goals for the day

Global ChangesGlobal 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 CauseGlobal Change Cause• What is the

Generative Force behind these changes?

US!US!

Human ImpactHuman Impact• We have altered nearly all of the Earth

that it is profitable for us to do so

Next Week: The Tour of Next Week: The Tour of Ecology ConcludesEcology Concludes

• Population ecology

• Community ecology

• Ecosystem ecology

• Conservation Issues– Next week’s

emphasis– Is there any hope for

the future?

Documents

Introduction to Ecology