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									Pickerelweed – Lower Mississippi
       River Bottomlands
Bottomland Forests
Shawnee Hills
Shawnee Hills
Thread-leaved Evening Primrose -
         Shawnee Hills
Coastal Plain at Cairo
Bald Cypress – Coastal Plain
         Division
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 Type          Area (km2 x 106)
High grass savanna           7.25
Tallgrass savanna            10.10
Tallgrass prairie            4.09
Shortgrass prairie           3.11
Desert grass savanna         5.96
Mountain grassland           2.05
                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
• It 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
• 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 75 - 100 cm from Texas to
  Indiana and 50 - 65 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 – 60-100 cm precip
• - mixed grass prairie with grasses typically
  between 60 - 120 cm tall occurs in middle region
  with intermediate precipitation – 35-60 cm precip
• - shortgrass prairie with grasses less than 60 cm
  tall - at western margin with least amount of
  precipitation – 25-35 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
   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
       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

								
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