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