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Controls: climate. Controls: soils, parent material. Controls: topography. Controls: disturbance. Controls: humans. Self-scouring, steel-bladed plow.
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Controls: climate
Controls: soils, parent material
Controls: topography
Controls: disturbance
<0.01% of pre-settlement prairie in Illinois remains
Self-scouring, steel-bladed plow
Controls: humans
Controls: herbivory
Controls: microclimate
Controls are not constant; they have changed through time
For example:
• Continental drift• Mountain building and rain shadows• Climate change• Human alteration to land cover; greenhouse gas
emissions
Biomes during last glacial maximum
Trees following last glacial maximum
Latitudinal movement of the solar equator causes seasons
Solar equator moves seasonally
Seasonal cycles in temperate lakes
clockwise
counter-clockwise
upwelling
Variation in temperature generates winds.
Winds drive ocean currents, which redistribute heat and moisture.
Upwelling currents bring cold, nutrient-rich water to the surface & lead to high productivity
Effects of El Niño on climate
Effects of El Niño on crop production
Stronger El Niño events in recent decades
Fundamental niches and climatic envelopes for hypothetical 20th- and 21st-century climates
Williams et al. 2007. PNAS.
• Shifts in distributions (1-3)
• Communitydisaggregation (1 & 3)
• New communities (2 & 3)
• Extinction (4)
Maps of novel 21st-century climates and disappearing 20th-century climates
Assumes no dispersal limitation; w/ disperal limitation the %s approx. double
12-39%
10-48%
4-20%
4-20%
Williams et al. 2007. PNAS.
Summary
• Ecosystems are complex, resulting from many interacting factors
• Ecosystems and their controls are not constant; they have changed through time
• Humans now have a dominant influence on Earth’s climate and ecosystems
• The present helps us interpret the past and anticipate future changes