Composition of the Atmosphere

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Science News
http//www.nytimes.com/2009/01/23/us/23trees.html?
refscience http//www.sciencemag.org/cgi/content
/abstract/323/5913/521
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1.3 Current views

• Gleasons view is more broadly accepted by modern
  biogeographers and ecologists
• But Clements
• views still lives on
• in many aspects
• of management
• and research
• What do you think?

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Geography of Communities (GEOG 302, 2 Feb.,
2009)?

• 1. Communities
• 1.2 Variations in space and time
• 1.3 Current views
• 2. Ecosystems
• 2.1 Properties
• 2.2 Patterns and
• energy flow
• 2.3 Diversity and
• function

Deer and sagebrush in Yellowstone National Park.
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2. Ecosystems

• Ecosystem community physical chemical
  environment
• defined by processes linking organisms, but
  generally arbitrary. Fits multiple scales.

Mammal community (Class) Grazer community (guild)
Northern Yellowstone Ecosystem
Plant community (Kingdom) Producers community
(guild)
Deer and sagebrush in Yellowstone National Park.
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2. Ecosystems
Ecotone gradual change from one ecosystem to
another
http//gf.state.wy.us/wildlife/wildlife_management
/Grizzfinal_files/image021.gif
Montana State University, Big Sky Institute
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2.1 Ecosystem properties

• Structure static properties
• Diversity (various metrics species richness,
  evenness)
• Species Composition (number, proportion)
• Soil type
• Biomass (area, mass)
• Size (diameter, height)

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2.1 Ecosystem properties

• Function dynamic processes
• Productivity
• Decomposition
• Carbon uptake
• Phosphorus cycling

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2.1 Ecosystem properties

• Ecosystem Function
• Energy Flow sun ? producers ? consumers ?
  decomposers
• Nutrient Cycling
• carbon, oxygen,
• nitrogen,
• phosphorous

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http//www.globalchange.umich.edu/globalchange1/cu
rrent/lectures/kling/ecosystem/ecosystem.html
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2.2 Patterns and energy flow

• Energy Flow trophic pyramids and food webs
• carrying capacity units of useable energy in a
  system

Energy (Kilocalories m-2 yr-1)
Similar to textbook Fig. 5.6
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2.2 Patterns and energy flow

• Large organism require lots of energy

m cM0.75 m basal metabolic rate c
constant (taxon-specific) M biomass 0.75
scaling exponent It takes about 14,000 times
more energy to maintain a 5000 kg elephant than a
15 g mouse It requires 25 X more energy to
maintain 1 g of mouse than one gram of elephant
Metabolic rate (cal / hr)
Body mass(g)
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Modified from Hemmingsen (1960)
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2.2 Patterns and energy flow

• Energy and Ecosystem Structure
• More energy ? more species (diversity)
• More energy ? greater abundance of large animals
• Large organisms ? large and/or productive
  ranges

Puma concolor
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http//en.wikipedia.org/wiki/Cougar
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2.2 Patterns and energy flow

• Energy and Ecosystem Structure
• more small than large animal species

Terrestrial mammals. global
Terrestrial birds, global
Number of Species
Terrestrial animals, global
Beetles in Great Britain
Body length (mm)
(May, 1978)
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2.3 Diversity and ecosystem function

• Hypothetical relationships between biodiversity
  (a structural measure) and ecosystem function

Redundant Species Hypothesis
Equal Importance Hypothesis
Rivet Hypothesis
Rate of ecosystem function
Removal of a keystone species
Measure of biodiversity e.g. of species,
species evenness
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2.3 Diversity and ecosystem function

• Empirical relationships between
• species richness (a structural measure) and
  productivity (a functional measure)

Biomass accumulation (g/time)
Experimental grassland ecosystem in the midwest
Species Richness
Symstad et al., 1998. Species Loss and Ecosystem
Functioning Effects of Species Identity and
Community Composition. Oikos, 81 389-397.
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2.3 Diversity and ecosystem function

• Ecosystem stability ? some measure of how
  resilient an ecosystem is to change

Alaskan boreal forest ecosystem, three years post
fire.
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2.3 Diversity and ecosystem function

• Empirical relationships between
• species richness (a structural measure) and
  stability (a functional measure)

Biomass ratio (post / pre drought)
Drought resistance
Experimental grassland ecosystem in the midwest
Pre-drought species richness
Tillman and Downing, 1994. Nature
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QUIZ

• Which of the following is an example of ecosystem
  function
• Species diversity
• Productivity
• Size distribution of organisms
• Species composition
• None of the above

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QUIZ

• 2. According to the graph, the addition of
  additional species to an ecosystem
• Increases ecosystem function at an equal rate
• Has no impact on ecosystem function
• Is redundant after a certain number of species is
  added
• Only increases
• ecosystem function
• with the addition of
• particular species

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QUIZ

• 3. The graph below suggests what about the
  environmental gradients, species distributions,
  and community organization
• Environmental gradients, interspecific
  competition, and coevolution
• Environmental gradients and interspecific
  competition
• Environmental gradients and coevolution
• Individual species response to environmental
  gradients little or no coevolution

Density of individuals
Environmental gradient across space
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Summary

• Communities
• Useful concept, not always applicable
• Deterministic vs. Individualistic species
  organization
• Ecosystems
• Applicable across spatial scales
• Structure and Function are different, but related
  properties of an ecosystem (or community)
• Ecosystem Function ? energy flow, nutrients
  cycling, stability