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Chapter 19
Ecosystem Essentials
Geosystems 6eAn Introduction to Physical Geography
Robert W. ChristophersonCharles E. Thomsen
Ecology
Study of relationships between organisms and their abiotic environment
Can be studies at several levels:PopulationCommunityEcosystemBiosphereFig 1.8
CommunitiesFig. 19.3
Community TermsHabitatType of environment where an organism residesNicheFunction of a life form within a community
In stable community, no niche is left unfilled
Competitive Exclusion Principle applies:No two species occupy same niche at same time
Interactions in communitiesCompetitionNegative for both species (/)
Symbiotic/Mutualistic (+/+)Both species benefitlichen (fungi and algae)
Predation (+/)One benefits, one loses
EcosystemFigure 19.2
Plants (Vegetation)Critical biotic link between solar energy and the biosphereBase of vast majority of food websAbout 20 species of plants provide 90% of the human food supplyWheat, corn (maize), and rice are halfConvert carbon dioxide to oxygenTranspiration elevates atmospheric humidity
Photosynthesis and RespirationFigure 19.5
Distribution of VegetationFive major factors:Climate (temperature and precipitation)Topography (elevation, slope)Soils (nutrients, minerals)Biotic Influences (dispersal mechanisms)Disturbance (natural or anthropogenic)
ClimateFigure 19.8
Life ZonesFigure 19.9
Carbon and Oxygen Cycle
Climate ChangeFigure 19.23
Whats limiting these distributions?Figure 19.12
Soils nutrients, mineralshttp://www.cfr.washington.edu/Classes.esc.520B/ImagesNorthFork/Serpentine6SM.jpghttp://www.krisweb.com/krisnavarro/krisdb/ac/dscn2166_sm.jpghttp://nrs.ucdavis.edu/mclaughlin/images/plants/Seep.jpgSerpentine
Dispersal Mechanisms Fruit and Seedhttp://www.cas.vanderbilt.edu/bioimages/pages/fruit-seed-dispersal.htm
What about this fruit?Osage orange (Hedge apple)These huge fruits ooze sticky, white latex when bruised. They are large and hard - what would want, or be able to eat them? Probably were once dispersed by extinct megafauna (large mammals) that died out soon after humans arrived in North America. http://www.cas.vanderbilt.edu/bioimages/pages/fruit-seed-dispersal.htm
Extinct Megafaunahttp://sscl.berkeley.edu/~anth122/mammoth.gifhttp://www.intersurf.com/~chalcedony/gomp.jpghttp://mishilo.image.pbase.com/u36/zidar/upload/23675731.pbtooth1.jpgMammothGomphothereTooth
Disturbance
NaturalWater, wind, volcano, fireAnthropogenic (human-caused)Deforestation, fire, development
SuccessionEcological succession when newer communities replace older communities of plants and animalsPrimary succession an area of bare rock or disturbed site with no previous communitySecondary succession some aspects pf a previously functioning community are present
Succession
End Chapter 19Geosystems 6eAn Introduction to Physical Geography
Robert W. ChristophersonCharles E. Thomsen