Ecology Unit 4.docx - Ecology Unit 4 Chapter 18: Community...

This preview shows page 1 - 5 out of 46 pages.

The preview shows page 3 - 5 out of 46 pages.
Ecology Unit 4 Chapter 18: Community Structure Community structure oCommunity diversityincludes both the number and relative abundance of species oResources, habitat, keystone species and disturbances can play roles in organizing communitiesoCommunities are organized into food webs Terrestrial community organization changes with altitude, which impacts:oTemperatureoWindoSoil moisture Aquatic community organization changes with depthoSpecies distributions may be limited by abiotic interactions i.e. the tides Upper intertidal zonesoAlso may be limited by biotic interactions like competition and predation Lower zones An ecotoneis the distinct boundary between communities oPlant biology oCan be caused by abrupt changes in conditions like soil composition
Serpentine(rocky) soil prevents tree growth oSome species prefer theecotone to the adjacenthabitats, but why?oMost likely due tocompetitive exclusion atone time Forced into lessthan ideal territorydue to competitionbetween speciesand adapt to thenew environment oSome species are adapted toall 3 types of soils Hawkweed, Fescue, andSnakeroot treesDue to many reasons but often related to the evolutionary history of that species Species within communities may be interdependentor independentoTree speciesappeared anddisappearedthroughout thestudy areaaccording to themoisture gradientbut withoutreference to each other 2
The trees are independent of one anotherCan subsist without each other just fine Stability of community is not dependent on each species abundance oInterdependencecan be measured as survival and reproduction ratesExtreme environments (high elevations), neighbor removal hurts survival and reproductive efforts of the focal species Low elevation, neighbor removal increases reproduction of focal species Plant is released from competitionRank-abundance curves can be used to tease apart species evenness and relative abundance oWidth of each curve indicates the species’ richness (how many of that species you actually have) oSpecies abundance: how many of each type?oSpecies evenness: are all species in the community equally abundant? oLog-normal distribution: most species have neither very few or very many individuals within the community Normal bell curve While species richness may be identical, species evenness may still vary between communities 3
oTheoretical comparison: Community A has5 species, 1 is muchmore abundant Community B has5 species, all equallyabundant Therefore,community B hasgreater species evenness oLizards in Brazil: Eucalyptus plantation is moreeven Primary forest is morespecies rich Calculating diversity oSimpson’s diversity index(D)A simple mathematical measure that characterizes species diversity in a community The proportion of species, I, relative to the total number of species, pi, is calculated and squared

Upload your study docs or become a

Course Hero member to access this document

Upload your study docs or become a

Course Hero member to access this document

End of preview. Want to read all 46 pages?

Upload your study docs or become a

Course Hero member to access this document

Term
Spring
Professor
Yurasits
Tags
Ecology, NPP, Ecological succession, Glacier Bay, o Wind

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture