Patterns in Ecosystems

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Patterns in Ecosystems
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Zonation

• Changes in biota that occur when along a
  gradient parallel to the surface.
  
• Consider the zones seen in the vegetation at the
  pond. Similar zones can also be seen at the bog.

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Kettle-hole Bog

• Zones can also be seen at the bog.
• Trees/ tall shrubs, shrubs, mat, edge, water

Wednesday
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Salt Marsh
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Salt Marsh
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Vegetation changes with increasing altitude

North
South
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Vertical zonation

• In this case the change is still parallel to the
  surface, but the surface is in vertical
  orientation

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Zonation - (cont)

• Bands of vegetation are often seen in the Taiga
  region and alpine environments -
  
• Alternating bands of mature coniferous trees and
  grass and shrub vegetation.
  
• Tree bands have mature trees to the windward side
  and then progressively younger trees to the
  leeward side until one reaches grass and shrubs.
  
• The windward side is characterized by dying trees
  along the front edge.
  

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Fir Bands

• Mtns. In New Hampshire

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Wind dessication Rime ice
Build up of protecting snow to the leeward and
the desiccation of trees to windward side.

• Rime ice builds up on branches exposed to wind

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Young grow under dead trees

• Young fir benefit from the increased light and,
  when small, the protection of snow cover.

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Stratification - perpendicular to surface
Maple, Oak, Beech
Basswood
Viburnum

• Changes of light, moisture, temperature occur
• Particularly dramatic in tropical rainforests and
  aquatic systems

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Dispersion Patterns

• Random - position of an individual is independent
  of the others
  
• rare condition for organisms
• insects, spiders, some clams
• usually associated with a random and plentiful
  food supply
  
• can be found in low abundance tropical forest
  species

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Clumped (aggregated, contagious, clustered, under
dispersed)

• Varies in the degree of clumping
• Plant reproduction - seeds
• Some animals tend to be clumped for
  reproduction.
  
• Advantages help in obtaining food protection
  (to fend off, or simply to reduce the chance of
  the individual being taken) migration
  
• Disadvantages attracts predators disease
  spreads easily
  
• Clumps may be found secondarily in random,
  clumped or uniform patterns

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Uniform (over dispersed)

• Usually a result of intraspecific competition.
• Personal space may also be desired.
• Plants - usually a result of strong competition
  for root and shoot resources
  
• May also come from reaction to something the
  plants put into the soil (allelopathy)

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Changes in dispersion patterns

• Larvae
• Hawaiian Honeycreeper - depends on the abundance
  of the food source (nectar).
  
• Organism pattern indicates the interaction it has
  with other organisms or, something about its seed
  dispersal.

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Typical Wednesday