Introduction to Ecology

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 • But Before That…. • Let’s Discuss the Population Growth • and Forensic Entomology Exercises

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 • Describe forensic entomology and degradative succession. Why is this an example of it? • 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. • 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?

Predator Herbivore Producers 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

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 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?

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.

Population Community Ecosystem Biome Biosphere Ecological Pyramid • Trends down pyramid: • Increase in geographicscale • From single species to multiple species • Increasing number of ecological factors that may be influential • Decreasing certainty in results Where do Biomes Fit?

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?

Introduction to Ecology