Ecological Background of Southwestern Illinois

Important Ecological Zones
•	Large Rivers:  Mississippi, Missouri, Illinois
•	Mississippi Borderlands
•	Prairie Peninsula

Illinois 16,000 years ago (spruce and mastodon)

•	Dry period 5000-3000 years ago 
•	allowed migration of prairie flora into Illinois
•	Fire maintains prairie border when weather becomes wetter

Important Ecological Zones
•	Large Rivers:  Mississippi, Missouri, Illinois
•	Mississippi Borderlands
•	Prairie Peninsula

Mississippi and other Large Rivers
•	Feature floodplain and terraces

Characteristics
•	Natural river flood cycle
–	Spring (April) flood
–	Smaller, sometimes absent, fall (October) flood
•	Natural floods lower, but longer lasting

Characteristics
River floods critical to life of river
	1. Sand bars where current is fast
	2.  Cut new channels
	3.  Deposit sediment on floodplain
	4.  Flood depressions on floodplain

Sandbars
•	Disturbance specialist plant species  (*denotes sight ID quiz)
–	Cottonwood (Populus deltoides)*
–	Willows (Salix spp.)*
–	Grasses, weeds (knotweed, burr rush, etc.)
•	Habitat for birds (Red-winged blackbird, ducks, geese, wading birds)

Remodeling of River Channel
•	More land-water interface 
–	greater species diversity
•	New habitat in abandoned channels
–	sloughs  and oxbow lakes
–	breeding habitat for fish, amphibians, fowl

Dominant Species of Floodplain Grasslands

Important Floodplain Trees (1)  (*denotes sight ID quiz)
	Green ash (Fraxinus pennsylvanica)*
	Silver maple (Acer saccharinum)*
	Boxelder  (Acer negundo)*
	Southern pin oak (Quercus palustris)*
	Bald cypress (Taxodium distichum)
	Pecan  (Carya illinoensis)

Important Floodplain Trees (2)
Important Floodplain Trees (3)

Effects of Levees and Water Control
•	Shut off flooding cycle to floodplain
•	Change water flow in rest of river
–	Unnatural floods (summer?!)
–	Extreme floods (1993)
•	Prevent formation of new habitats, sediment deposition, reduce habitat
Mississippi and other Large Rivers
•	Levee effects

Most scientists agree that big rivers without a semblance of a natural flood cycle are doomed.  

Can the public find some way to make it work?

Mississippi Borderlands

Vegetation is Maintained by Occasional Fire
•	Perhaps a 20-50 year return time
•	Fire is selective
–	Moderately harmful to mature oaks and hickories
–	Harmful to saplings and shade tolerant trees

Dominant Species (1) (*denotes sight ID quiz)
	White oak  (Quercus alba)*
	Red oak  (Quercus rubra)*
	Hickory  (Carya)*

Dominant Species (2)

Prairie Peninsula

Approximate Boundary of the Prairie Peninsula
Characteristics
•	Tall grass dominated (6-9 feet in late summer)
•	Plants in large tufts, forming a dense mat of roots
•	Grasses photosynthetic pathway conserves water, and is very efficient at high temperature
•	Grazing animals:  Bison, elk

Poaceae (Grass Family)

Asteraceae (Sunflower Family)

Fabaceae (Legume family)

Prairie fires:  hot, fast, and high

Why does fire benefit grasses and forbs, but not trees?
•	Herbaceous plants put most biomass below ground--not burned in fires
•	Buds below soil 
•	Fire tolerant trees: thick corky bark, resprout

Dependence on fire creates a landscape mosaic

•	Valleys provide a refuge for forest 
•	Rivers are fire barriers
•	Clusters of oak trees (“oak openings”)

Key theme:  river systems determined prairie/forest mix in Illinois