biology 403 principles of ecology communities succession biomes
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BIOLOGY 403: PRINCIPLES OF ECOLOGY (Communities, Succession, Biomes)

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

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communities
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
ecotone
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
emerging characteristics in communities
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
ecological succession iii1
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
ecological succession iv
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 ?????)
climax communities i
CLIMAX COMMUNITIES (I)
  • DEFINITION:dynamic 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
climax communities ii
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
trends during succession i
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
trends during succession ii
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 > R P = R
physiognomic types of vegetation i
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)
physiognomic types of vegetation ii
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
physiognomic types of vegetation iii
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
biomes
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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