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


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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