Illinois Plant Communities – Prairie Ecosystems

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 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 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

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.6 and.8 for tallgrass prairie regions

Microclimate

Primary Production Grasses occur in two basic forms - sod (or turf) grasses form a thick mat - bermuda grass bunch grasses grow in distinct clumps - little bluestem sod grasses usually grow vegetatively with short rhizomes, stolons or runners and are very effective in resisting water or wind erosion bunch grasses reproduce vegetatively by tillers - shoots which arise from the crown - basal portion of plant, atop the roots - may have up to 100 or more tillers in a single clump of grasses like little bluestem

Sod grass vs. bunch grass

Grass tillersSpread by rhizomes

Primary Production Gross primary production (GPP) is the total amount of energy fixed by a plant or plant community Net primary production - is the amount of energy stored or biomass produced - it is GPP minus energy burned in respiration NPP = GPP - R

Ecosystem Production Gross Ecosystem Production (GEP) - is total energy fixed in ecosystem Net ecosystem production (NEP) is total amount of energy stored or biomass produced by all organisms in ecosystem - producers, consumers, decomposers - or GEP - ecosystem respiration (ER) the respiration of all plants, consumers and decomposers NEP = GEP - ER

Prairie Productivity Estimates of production of aboveground biomass range from 200 to 570 grams of carbon per square meter per year for a tallgrass prairie

Prairie Productivity In prairies 2 to 4 times the amount of aboveground biomass occurs as biomass below ground Prairie plants produce extensive root systems - big bluestem roots reach down 2 m; switchgrass roots reach down 3.7 m; forbs such as leadplant and dotted gayfeather have much deeper roots - reaching down 5 m A student of Weaver's measured the length of root material in the top 10 cm of a 0.5 square meter plot and found 21.5 km of big bluestem root; 38.7 km of little bluestem; 18.3 km of needlegrass; km of Kentucky bluegrass

Prairie Productivity In prairies belowground biomass of 685 to 1900 g C per square meter per year Thus total yearly production in tallgrass prairies combining aboveground and belowground biomass appears in the 800 to 2400 g C per square meter per year range This is in comparison to 3500 g C per square meter for an Iowa cornfield

Influence of grazing

East African Grasslands

Grazing in Illinois Prairies Illinois tallgrass prairie plants vary in response to grazing - ability to withstand grazing depends upon several factors: 1. possession of rhizomes 2. capacity for production of lateral shoots 3. small height and erectness of growth habit 4. lateness of seed germination and spring growth 5. slow growth rate 6. lateness of elevation of stem apex above minimum point of grazing

Decline with Grazing Indian grass Willow aster

Increase with Grazing Sideoats gramaCommon Yarrow

Highly invasive after grazing Downy Brome (cheatgrass) Canada Thistle

Eastern Meadowlark Dickcissel Increase with moderate grazing

Grasshopper sparrow – Only found in grazed areas

Savannah sparrow Declines with grazing

LeConte’s SparrowBobolink Unaffected by grazing

Decline with grazing Prairie Vole Short-tailed shrew

Unaffected by grazing Thirteen-lined ground squirrelWhite-footed deer mouse