Chapter 19 “Ecosystem Essentials” Geosystems 6e An Introduction to Physical Geography Robert W. Christopherson Charles E. Thomsen

Ecology Study of relationships between organisms and their abiotic environment Can be studies at several levels: Population Community Ecosystem Biosphere Fig 1.8

Communities Fig. 19.3

Community Terms Habitat Type of environment where an organism resides Niche Function 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 communities Competition Negative for both species (–/–) Symbiotic/Mutualistic (+/+) Both species benefit lichen (fungi and algae) Predation (+/–) One benefits, one loses

Ecosystem Figure 19.2

Plants (Vegetation) Critical biotic link between solar energy and the biosphere Base of vast majority of food webs About 20 species of plants provide 90% of the human food supply Wheat, corn (maize), and rice are half Convert carbon dioxide to oxygen Transpiration elevates atmospheric humidity

Photosynthesis and Respiration Figure 19.5

Distribution of Vegetation Five major factors: Climate (temperature and precipitation) Topography (elevation, slope) Soils (nutrients, minerals) Biotic Influences (dispersal mechanisms) Disturbance (natural or anthropogenic)

Climate Figure 19.8

Life Zones Figure 19.9

Carbon and Oxygen Cycle

Climate Change Figure 19.23

What’s limiting these distributions? Figure 19.12

Soils – nutrients, minerals Serpentine

Dispersal Mechanisms – Fruit and Seed

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. What about this fruit?

Extinct Megafauna Mammoth Gomphothere Tooth

Disturbance Natural Water, wind, volcano, fire… Anthropogenic (human-caused) Deforestation, fire, development…

Succession Ecological succession – when newer communities replace older communities of plants and animals Primary succession – an area of bare rock or disturbed site with no previous community Secondary succession – some aspects pf a previously functioning community are present

Succession

End Chapter 19 Geosystems 6e An Introduction to Physical Geography Robert W. Christopherson Charles E. Thomsen