Ecosystems: Definition, Processes Forest Ecosystems: Importance on a Global Scale

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EcosystemsDefinition, ProcessesForest
Ecosystems Importance on a Global Scale

• Aspen forest

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Definition of Ecosystem

• An ecosystem is a community of interacting
  species, taken together with the physical
  environment within which it exists and with which
  the species composing the community also
  interact (Perry 1994)

Tongass National Forest Alaska
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Definition of Ecosystem

• A conceptual unit comprised of organisms
  interacting with each other and their
  environment, having the major attributes of
• structure
• function
• complexity
• interaction
• interdependency
• temporal change
• no inherent definition of spatial dimension

Gallatin National Forest Mountain Pine Beetle
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Ecosystems

• Individual organisms or species generally are not
  able to perform all of the functions that are
  needed to sustain life
• They tend to group together into communities in
  which they interact with each other and their
  environment

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Forest watershed - A large and complex ecosystem
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Why study forest ecosystems?

• Forest provide wood, food, habitat, fuel,
  pharmaceuticals, recreation
• Forests affect the movement and transformation of
  water, energy and nutrients

Roosevelt ElkOlympic National Park
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Why study forest ecosystems?

• Trees capture and store more carbon than any
  other type of plant

Rogue River National Forest, Oregon
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Why study forest ecosystems? Global heat balance

• Forests account for approximately 70 of the
  Earths leaf surface area
• In relatively moist environments, forests support
  from 2 to 10 times more leaf area per unit of
  land than do grasslands

George Washington National Forest, Virginia
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Why study forest ecosystems?Global heat balance

• Leaves absorb a much higher proportion of the
  suns energy than does bare ground
• Forests absorb 75-93 of incident solar energy,
  a higher proportion than other vegetation type.
• Only about 2 of this energy is used in
  photosynthesis most of the energy is used to
  evaporate water, which is then moved around the
  globe.

Rainforest
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Why study forest ecosystems?

• Forests therefore greatly affect the Earths heat
  balance, hydrologic cycles and climate

Ross Creek Western Redcedar GroveWestern Montana
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Why study forest ecosystems? Hydrologic cycle

• Forests account for the majority of
  evapotranspiration from land and thereby affect
  rainfall patterns on land
• Leaves transpire water back to the atmosphere
• Leaves provide surfaces on which water vapor
  condenses and therefore returns to the earth
• Trees enhance the water-storage capacity of
  soils, thereby preventing floods and erosion

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Forest Ecosystem Management

• Forest ecosystem management involves the use of
  an ecological approach to forest resource
  management
• at the landscape level
• that blends biological, physical, social, and
  economic processes
• to ensure the sustainability of healthy forest
  ecosystems
• while providing desired values, goods and
  services to society

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Managing ecosystems requires knowledge of

• Physical properties

Biological organisms
Functional processes
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Basic concepts in ecosystem management

• 1. Sustainability Sustainability refers to
  resiliency of ecosystems their capacity to
  recover from disturbance and the rate at which
  they restore ecological processes to a
  pre-disturbance condition
• Ecosystems are sustainable if we understand their
  dynamics and manage them skillfully
• When a forest is managed for sustainability, it
  retains productivity, diversity and overall
  integrity in the long run.

Loxahatchee River Florida
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Basic concepts in ecosystem management

• Goals of ecosystem management that may be
  sustainable are
• Maintaining a mix of ecosystem goods, functions
  and conditions that society wants
• Maintaining evolutionary and ecological processes
• Maintaining viable populations of native and
  non-native species

Rogue River N.F.Oregon
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Basic concepts in ecosystem management

• Change
• Ecosystems change whether they are managed or not
  
• Ecosystems are both dynamic and resilient
• Disturbance elicits response - both are natural
  to ecosystem function

Mt. St. Helens scorched forest
Mountain Pine Beetle kill
Mt. St. Helens before and after blast
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Basic concepts in ecosystem management

• 3. Ecosystems are complex
• They vary in size
• There are linkages among parts
• They include biological and physical diversity
• Many processes are involved
• They can be studied on different scales

Willamette N.F.
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Basic concepts in ecosystem management

• 4. Ecosystems have biophysical, economic and
  social limits
• Society wants goods and services
• Ecosystems can provide only a limited amount of
  these before they begin to deteriorate
• Understanding the limits of an ecosystem helps us
  to make wise management choices
• Understanding the potential of an ecosystem helps
  us to manage to provide broader array of choices

Soil Erosion
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Basic concepts in ecosystem management

• 5. Ecosystems are not fully predictable
• Even the best models are still only
  approximations based on a variety of assumptions

Flooding caused by beaver dam
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High elevation spruce-fir forest in north Idaho
Ecosystem Management ONE SIZE DOES NOT FIT ALL
Lodgepole pine 18,000 stems per acre
300 year-old ponderosa pine - Oregon
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Photo Credits

• Thinkquest.org
• Americanlands.org
• www.uwsp.edu/Geography 101
• ForestryImages.org
• Photo-guide.com
• www.bugwood.org