BIOLOGY 403: PRINCIPLES OF ECOLOGY (Communities, Succession, Biomes)

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BIOLOGY 403 PRINCIPLES OF ECOLOGY
(Communities, Succession, Biomes)
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COMMUNITIES

• DEFINITION
• a community is a unit composed of two or more
  interacting species in a given area
• Communities have boundaries in space and time.
• How many communities are there on the earth?
• One ???
• Millions ???
• Ecotone
• zone between communities where composition very
  rapidly changes from that typical of one
  community to that typical of the other

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ECOTONE

• A pressure zone(an intermediate / intergrading
  area)
• May be narrow or wide
• May have larger flora / fauna than adjacent
  communities --- WHY ???
• May have species unique to it

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EMERGING CHARACTERISTICS IN COMMUNITIES

• Dominant ( Keystone) Species / Subordinant
  Species
• Stratification ( Layering)
• Phenology (rhythmic seasonal patterns)
• Succession
• a non-cyclic process in which species /
  communities in a particular area are replaced by
  other species / communities over time (the life
  history of a community)
• Sociability --- the or affinity one species
  has for another

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ECOLOGICAL SUCCESSION (I)
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ECOLOGICAL SUCCESSION (II)
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ECOLOGICAL SUCCESSION (III)
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ECOLOGICAL SUCCESSION (III)

• What causes it?
• Organisms and the changes they create are the
  driving force.
• Types of Succession
• Primary
• occurs on a primary bare area
• Secondary
• occurs on a secondary bare area

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ECOLOGICAL SUCCESSION (IV)

• Sere - the whole sequence of communities in a
  particular succession (Xerosere, Mesosere,
  Hydrosere) OFTEN X ??? M ??? H
• Pioneer (species of community)
• the first species to invade an area
• Seral (species or community)
• those which occupy intermediate positions in a
  succession (early, mid, late, etc.)
• Climax (species or community)
• those occupying the final position in a
  succession(Monoclimax or Polyclimax ?????)

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CLIMAX COMMUNITIES (I)

• DEFINITIONdynamic steady state community whose
  characteristics are determined by the
  characteristics of its habitat / environment
• Primary Climax
• do not depend on recurrent disturbances by fire
  or animals to maintain floristic / faunal
  composition
• Climatic Climax --- on normal soils, with average
  topography, and thus only the macroclimatic
  conditions are controlling it.
• Edaphic Climax --- develops differently from what
  one expects for the macroclimatic conditions due
  to an unusual soil
• Topographic Climax --- develops differently from
  others in the same region due to a distinctive
  microclimate

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CLIMAX COMMUNITIES (II)

• Disclimax
• all climaxes that maintain their floral / faunal
  composition only as a result of persistent
  disturbances of the same kind, frequency and
  intensity
• - Fire
• NJ Pine Barrens
• Some Grasslands
• - Zootic
• Some Grasslands

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TRENDS DURING SUCCESSION (I)

• Stage in
  Ecosystem DevelopmentAttribute
  Young
  Mature-------------------------------------------
  -------------------------------------
• Biomass low
  high
• Trophic Relationships simple
  complex
• Food Chains short,
  grazing long, detritus
• Food Webs simple
  complex
• Stratification less
  more
• Species Diversity low
  high
• Niche Specialization broad
  narrow
• Feeding Relations general
  specialized
• Life Cycles short,
  simple long, complex
• Population ControlMechanisms
  physical biological

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TRENDS DURING SUCCESSION (II)

• Stage in
  Ecosystem DevelopmentAttribute
  Young
  Mature-------------------------------------------
  -------------------------------------
• Fluctuations greater
  lesser
• Stability low
  high
• Potential Yield toHumans
  high low
• Net CommunityProduction
  higher lower (0 ??)
• Community Respiration lower
  higher
• Community P / R Ratio P gt R
  P R

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PHYSIOGNOMIC TYPES OF VEGETATION (I)

• Physiognamy --- landscape appearance due to
  occupying vegetation type(s)
• Forest --- tall trees covering the area densely
  and uniformly (needle-leaved, broadleaved
  evergreen, broadleaved deciduous OPEN vs.
  CLOSED)
• Woodland when trees are of a lower stature
• Gallery forest or woodland --- in a strip along
  stream courses (subdivided as in forest)

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PHYSIOGNOMIC TYPES OF VEGETATION (II)

• Savanna --- singly scattered trees or shrubs over
  a more continuous phase of low vegetation
• Groveland --- clusters of trees or shrubs
  scattered over a more continuous phase of low
  vegetation
• Parkland --- islands of low vegetation (the
  PARKS) interspersed in a more continuous phase of
  forest

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PHYSIOGNOMIC TYPES OF VEGETATION (III)

• Scrub (Shrub) area covered by lower growing woody
  vegetation (subdivided as in forest)
• Grassland --- herbs are the dominant vegetation
• Steppe --- xerophytic herblands (usually
  dominated by narrow- leaved grasses)
• Meadow --- Mesophytic herblands (usually
  dominated by broader-leaved grasses and forbs)
• Shrub-Steppe --- mixture of low shrubs and
  grasses sharing dominance in an arid area

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BIOMES

• DEFINITION
• a large area, on land, characterized by certain
  dominant climax plant species
• why characterized by the plants instead of
  animals????????
• The major Biomes
• see class handout for their names and the
  conditions causing them

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TEMPERATURE, MOISTURE AND BIOMES
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BIOMES OF THE WORLD
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LATITUDE, ALTITUDE BIOMES
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N. S. AMERICAN BIOMES
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DESERTS OF THE WORLD
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GRASSLANDS AND THEIR ORGANISMS