Community Ecology Chapter 9. Succession Temporal patterns in communities Replacement of species by others within particular habitat (colonization and.

Download Community Ecology Chapter 9. Succession Temporal patterns in communities Replacement of species by others within particular habitat (colonization and.

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  • Community EcologyChapter 9

  • Succession

    Temporal patterns in communitiesReplacement of species by others within particular habitat (colonization and extinction)Non-seasonal, continuous, directional

  • Degradative successionDecomposers breaking down organic matterLeads to disappearance of everything, species included

  • Autotropic successionDoes not lead to degradationHabitat continually occupied by living organisms

  • Two types of autotropic successionAllogenic succession

    Autogenic succession

  • Allogenic successionSerial replacement of species driven by changing external geophysical processes

    Examples:1) silt deposition changing aquatic habitat to terrestrial habitat2) increasing salinity of Great Salt Lake

  • Autogenic successionChange of species driven by biological processes changing conditions and/or resourcesExample: organisms living, then dying, on bare rock

  • Autogenic succession can occur under 2 different conditionsIn an area that previously did not support any communityPrimary successionExample: terrestrial habitat devoid of soilIn an area that previously supported a community, but now does notSecondary successionExample: terrestrial habitat where vegetation was destroyed, but soil remained

  • Primary successionVolcanic eruptions


  • SecondarysuccessionFloods


  • Rate of successionPrimary - slow - may take 1000s of years

    Secondary - faster - fraction of the time to reach same stage

  • Autogenic succession beginsFirst community comprised of r-selected species - pioneer species

  • r-selected speciesGood colonizersTolerant of harsh conditionsReproduce quickly in unpredictable environs

    Example: lichens

  • Pioneer speciesCarry out life processes and begin to modify habitatExtract resources from bare rockBreak up/fragment rock with rootsCollect wind-blown dust, particlesWaste products accumulateDie and decomposeSoil development begins

  • Continuing changeColonizers joined by other species suited for modified habitatEventually replace colonizersBetter competitors in modified habitatLess r-selected, more K-selected

  • More changeCommunities gradually become dominated by K-selected speciesGood competitors, able to coexist with others for long periods of time

  • StabilityCommunities become stabilizedReach equilibriumLittle or no change in species composition, abundance over long periods of timeClimax communityEnd stage of succession

  • Will climax stage be reached?Rarely is climax stage reached quicklySlow succession most common, climax stage almost never achievedCommunity usually affected by some major disturbance (e.g., fire) before climax stage is reachedResets succession, forces it to start again from some earlier stage

  • Terrestrial succession

  • Lake or pond succession


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