Illinois Plant Communities – Prairie Ecosystems

Illinois Native Ecosystems Today 2,352 high quality acres of remnant tallgrass prairie (less than 1/100 of 1% of the original) 918,000 acres of wetland (only 6,000 of high quality) 4.26 million acres of forest – but most of the forest is second growth that has developed since the 1940’s – only about 11,600 acres original old growth forest remains in Illinois

Grasslands Grasslands are biological communities and ecosystems containing very few trees or shrubs, characterized by herbaceous vegetation and dominated by grasses, family Poaceae

Grasslands Around the World

Types of Grassland Grassland TypeArea (km 2 x 10 6 ) High grass savanna7.25 Tallgrass savanna10.10 Tallgrass prairie4.09 Shortgrass prairie3.11 Desert grass savanna5.96 Mountain grassland2.05

The Grasses Grasslands contain about 600 genera and 7,500 species of grasses Grasses (Poaceae) occur from the polar regions to the tropics and comprise about 15% of the flowering plant species Poaceae is third in number of genera behind Asteraceae and Orchidaceae and fifth in number of species behind Asteraceae, Orchidaceae, Fabaceae, Rubiaceae (madder family - coffee and gardenias) Poaceae far surpass all other groups in terms of worldwide geographic coverage and percentage of total world vegetation cover

Grasslands Grasslands usually develop in areas with 25 to 100 cm of annual precipitation (10 to 40 inches) Grasslands are found primarily in plains in the interiors of continents and occur from sea level to 4,900 meters in the Andes (over 16,000 feet) Grasslands are typically located on deep, rich soils with simple profiles The soils are usually neutral to basic, high in organic matter, and thus are highly fertile

Grasslands Around the World

Grasslands 44% of Europe - mostly in the Ukraine, Hungary, Transylvania – but also in Spain 33% of South America - mostly pampas of Argentina but tallgrass prairie found in Uruguay and central Brazil, extensive savanna in Brazil 29% of Africa - but most is savanna and only 5% is prairie; most true prairie is in high veld of South Africa, but some occurs in east Africa 17% of Asia - mostly shortgrass steppes (prairies) 15% of North America is prairie - there are also more arid grasslands in western North America

Grasslands in North America

Prairie Limits Eastern margin of these grasslands typically has annual precipitation of cm from Texas to Indiana and cm farther north; roughly 75% of the precipitation occurs in the growing season As we move west, precipitation declines to about 25 cm near the Rockies and up to half of the precipitation falls out of the growing season All North American grasslands have a wet season followed by a period of drought or dry conditions - in Illinois, most precipitation occurs in spring, summer is somewhat drier

Prairie Types Decline in precipitation from east to west across prairies and Great Plains results in the center of the country having basically 3 different prairie types tallgrass or true prairie where grasses typically exceed 120 cm; on eastern end with most precipitation – cm precip mixed grass prairie with grasses typically between cm tall occurs in middle region with intermediate precipitation – cm precip shortgrass prairie with grasses less than 60 cm tall - at western margin with least amount of precipitation – cm precip

Prairie Plants Like all grasslands, prairies tend to be poor in diversity at the level of families - with 27% of the species being grasses - Poaceae; 19% being asters - Asteraceae; 10% being peas - Fabaceae But tallgrass prairie is very rich in numbers of species - there are about 265 species of grass and forb native to Illinois's tallgrass prairies - 72 of those species are grasses 95% of the tallgrass prairie plants are perennial plants with lifespans of around 20 years being common and some may live for more than a hundred years

Tallgrass Prairies Tallgrass prairie occurs in areas with a ratio of about 0.6 to 0.8 of precipitation to evaporation; peak precipitation in fall and spring, less precipitation in winter and summer; occasional droughts which may last up to 10 years occurring every 30 years or so; these climatic factors probably keep most woody plants out, while the prairie grasses and forbs are adapted to these "droughty" conditions

Tallgrass Prairie Grasses tallgrasses such as big bluestem Andropogon gerardi, Indiangrass Sorghastrum nutans, switch- grass Panicum virgatum mid-grasses such as little bluestem Schizachyrium scoparius, sideoats grama Bouteloua curtipendula, porcupine needlegrass Stipa spartea shortgrasses such as blue grama Bouteloua gracilis and hairy grama B. hirsuta

Tall Grasses Big Bluestem Indian grass Switchgrass

Mid grasses Little Bluestem Sideoats grama Porcupine Needlegrass

Short Grasses Blue grama Hairy grama

Grass Adaptations to Semi-Arid Conditions and Grazing Leaf cells (bulliform cells) allowed the leaves to roll up during drought to avoid desiccation basal meristem allowed leaves to recover and grow back following grazing basal meristem and silica content (opal) in plants probably evolved in response to grazing - silica to prevent or lessen grazing petals became modified into structures called lodicules which enabled the florets (small flowers) to open when moisture was favorable and close during times of excess moisture or drought

Bulliform Cells

Leaves curling due to desiccation – in corn

Worn high crowned tooth - from horse

More Grass Adaptations wind pollination developed because when living in areas with frequent drought, insect pollinators would be scarce - also winds are normally strong here grasses became modified to be efficient at asexual reproduction - clonal growth via runners and stolons seed dispersal by wind - caryopsis modified to have bristles which catch the wind - also modifications of caryopsis to allow dispersal by animals - rough awns and beards that catch on hair and feathers or skin major species have evolved broad tolerances and subsequently have wide geographic ranges

Climate of Tallgrass Prairies Weather is the sum total of the atmospheric conditions (temperature, air pressure, wind speed, moisture, and precipitation) over a short time period Climate is a longer term composite of the variety of day to day weather conditions

Climate in Illinois Climate in Illinois region is dominated by 4 major air masses - 1. maritime tropical air - warm, moist, unstable - from Gulf of Mexico and Caribbean 2. Continental tropical air - hot, dry, unstable - from northern Mexico and southwestern U.S. 3. Maritime polar air - cool, moist, unstable in winter, stable in summer - from northern Pacific 4. Continental polar air - cool, dry, stable - from northern Canadian tundra

Climate Details temperature - monthly maximum and minimum are lowest in January, max of 5.6 C and min of -4.4 C; monthly maximum and minimum are highest in July, max of 26.1 C and min of 13.3 C Illinois has about 180 frost free days in the center of the state - more in the south, fewer in the north Precipitation - minimum in January cm; maximum in June cm; with secondary maximum in September cm This dual peak of rainfall is very typical of areas dominated by tallgrass prairie

Key Climatic Characteristic A key climatic characteristic is the ratio of precipitation to evaporation - this is usually between 0.6 and 0.8 for tallgrass prairie regions

Microclimate

Soil Conditions Maximum soil surface temperatures occur in June at time of maximum of solar radiation; but maximum soil temperature at 200 cm depth doesn't occur until September Similarly minimum soil surface temperature occurs in January, but minimum soil temperature at 200 cm depth occurs in March - plant roots buffered from rapid and extreme changes in temperature Soil water content is maximum in spring - following rain and melt; soil water content is minimum in August - following period of active growth through somewhat dry summer