Download Ecosystem Ecology for Wildlife Scientists

Ecosystem Ecology for Wildlife
Scientists
Don White, Jr., Ph.D.
Key Concepts:
¾ An ecosystem is an association of organisms and
their environment
¾ Every ecosystem is an open system, in that it has
inputs and outputs of both energy and nutrients
¾ Energy flows in only one direction through an
ecosystem
Key Concepts:
¾ Each chain in a food web extends in a straight-line
sequence from producers through all the consumers
¾ Water, carbon, nitrogen, and phosphorus move
through geochemical cycles that are global in scale
¾ Each substance moves through a hydrologic,
atmospheric, or sedimentary cycle
¾ Humans are disrupting the natural cycles
The Nature of Ecosystems
¾ Primary
producers
¾ Consumers
¾ Decomposers
¾ Detritivores
Structure of Ecosystems
¾ Trophic Levels
• 1st - Primary producers
9Autotrophs
• 2nd - Primary consumers
9Herbivores, Decomposers, Detritivores
• 3rd - Secondary consumers
9Primary carnivores
• 4th - Tertiary consumers
9Secondary carnivores and parasites
Food Webs
¾ “ Network of crossing, interlinked food chains
involving primary producers, consumers, and
decomposers”
How Does Energy Flow Through an
Ecosystem?
¾ Primary source
• Grazing food webs
9Photosynthetic organisms to herbivores
• Detrital Food Webs
9Photosynthetic organisms to detritivores and
decomposers
Ecological Pyramids
Decomposers
Top carnivores
Primary carnivores
Herbivores
Primary Producers
Energy Flow at Silver Springs, Florida
Energy loss with
each trophic level
Geochemical Cycles
Hydrologic Cycle
¾ Rain and snow returns water to land
• Ocean currents and winds
• Evaporation
¾ Watershed
Deforested area had
greater calcium loss than
undisturbed area.
Sedimentary Cycle
¾ Phosphorus Cycle
• From land to sediments at bottom of the sea then back
to land
• Earth’s Crust
9Largest reservoir of phosphorus
Eutrophication
¾ Activities that increase the concentration of
dissolved nutrients
¾ Nutrient enrichment of any aquatic ecosystem
¾ Most minerals enter sedimentary cycles
¾ Fertilizers use phosphates
• Dense algae blooms
Carbon Cycle
¾ Aerobic respiration ------> Carbon dioxide
¾ Fossil fuel burning
¾ Volcanic eruptions
¾ Atmosphere, soils, plant biomass
• Largest holding stations for carbon
¾ Carbon dioxide fixation
• Photosynthetic autotrophs
From Greenhouse Gases to a Warmer
Planet?
¾ Greenhouse effect
Increase in CO2
Increase in CFC’s
From Greenhouse Gases to a Warmer
Planet ?
¾ Greenhouse effect
Increase in methane
Increase in nitrous oxide
Nitrogen Cycle
¾ N2 gases converted to usable forms
• Bacteria
9Nitrogen fixation
• Bacteria and fungi
9Decomposition
9Ammonification
9Nitrification
• Denitrification
Ecosystem Modeling
¾ Prediction of unforeseen effects of disturbance
¾ Computer programs
¾ Models
¾ Biological magnification
• Use of DDT
In Conclusion
¾ An ecosystem is an array of producers, consumers,
detritivores, and decomposers and their
environment
¾ Sunlight is the initial energy source for nearly all
ecosystems
¾ Feeding relationships are structured as trophic levels
in an ecosystem
In Conclusion
¾ Isolated food chains of who eats whom in an
ecosystem are rare in nature
¾ The rate at which primary producers capture and store
energy is the primary productivity
¾ Energy fixed by photosynthesizers passes through
grazing food webs and detrital food webs
In Conclusion
¾ Primary productivity depends on water and
nutrients
¾ Carbon dioxide is the main atmospheric gas in the
carbon cycle
¾ Burning fossil fuels and converting natural
ecosystems to farming and grazing add to
imbalances and may be factors in long-term global
warming
In Conclusion
¾ Nitrogen availability is a limiting factor for the total
net primary productivity of land ecosystems
¾ Most mineral elements enter sedimentary cycles and
become available
¾ Disturbances of an ecosystem can have unexpected
effects
¾ Computer modeling helps identify ecosystem
relationships and can incorporate them into models