BIOL 3500Ecology

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Lecture 18

• BIOL 3500Ecology
• Chapter 19 Landscape Ecology

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Learning Objectives

• Define
• Landscape ecology
• Turnover rate
• Corridor
• Contrast
• Edge, interior, and area-insensitive species
• Discuss
• Edge effect
• MacArthur Wilsons theory

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Landscape Ecology

• The study of patchiness within the landscape
• Studies the interaction between communities
• Definitely larger in spatial scale than community
  ecology
• Topozone.com can show us patchiness of CCSU and
  Morrow
• Note Reynolds Nature Preserve

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Edges

• Inherent edges occur due to some natural
  geographical features, and are largely permanent
• Induced edges are temporary, caused by
  disturbances
• Floods
• Fires
• Clear-cutting
• Livestock grazing

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Boundary

• A term from landscape ecology, for a zone having
  three components
• Border (an imaginary line, where two different
  patches meet)
• Both edges of the two adjoining patches
• Synonymous with ecotone coined by Clements for
  community ecology

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Types of Edges

• Edge a (forest to grasslands) high contrast
• Better for supporting more diversity
• Edge b (forest to forest) lower contrast
• Less vertical stratification
• Edge c is an advancing edge, and most diverse
• Highest diversity

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Some Animals Favor Edges

• Edges can offer easy access to at least two
  communities
• Ruffed grouse requires several habitat types
• Indigo bunting males need tall perches, females
  require thickets for nests
• Deer like corn fields for food, preferably near a
  patch of forest

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Habitat Fragmentation

• Some species require large habitat patches, and
  are affected by habitat fragmentation.
• Figure 19.6 shows a fragmented landscape

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Size of Patches

• Generally, large habitat patches have greater
  heterogeneity than small.
• Large carnivores especially at risk due to
  habitat fragmentation
• Small patches cannot contain enough territories
  for viable population.

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Edge and Patch Size

• Figure 19.7a b
• As patch size increases, ratio of edge to
  interior decreases.
• Small patches are all edge.

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Edge and Patch Shape

• Figure 19.7c
• More complex shapes increase the edge of a patch.
• What shape miniizes the amount of edge?

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Species and Their Edge Requirements

• Edge, interior, may hold different species
• Example data woodlands in Illinois Ontario from
  Robbins, et al.

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Edge Species

• Less likely to be encountered in large patches
• Include Gray Catbird and American Robin

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Interior Species

• More likely to be encountered in large patches
• Include Worm-eating Warbler and Ovenbird
• Some of these species require distance from edge
  for protection from nest-marauding racoons.
• Especially at risk from increasing fragmentation.

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Area-Insensitive Species

• Can be found in patches regardless of
  size.Include Carolina Chickadee and Eastern
  Wood-Pewee

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7th Inning Stretch
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MacArthur Wilsons Theory of Island Biogeography

• of species (S) on an island determined by two
  things
• Immigration rate this is controlled by distance
  to mainland
• Extinction rate this is controlled by the size
  of the island

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Discussing S

• Why is it that larger islands hold a greater
  number of species?
• Can extinction occur when an island is at
  equilibrium?
• Why might an island of given size and distance
  have fewer species than expected?

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Find the Corridors

• Corridor thin strip of suitable habitat
• Connects patches
• Sometimes act as filters
• Which patches are connected by a corridor
• See Topozone.com

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Metapopulation in Fragmented Landscape

• Some habitat patches support reproduction these
  are sources
• Some patches are attractive, but have higher
  mortality than birth rate these are sinks
• How might sinks give false impression regarding
  status of endangered species?