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Illinois Plant Communities


Bald Cypress Coastal Plain Division. Illinois Plant Communities. Prairie Ecosystems ... 2,352 high quality acres of remnant tallgrass prairie (less than 1 ... – PowerPoint PPT presentation

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Title: Illinois Plant Communities

Illinois Plant Communities Prairie Ecosystems
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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
  • 4.26 million acres of forest but most of the
    forest is second growth that has developed since
    the 1940s only about 11,600 acres original old
    growth forest remains in Illinois

  • 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
  • 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 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
  • 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
  • 15 of North America is prairie - there are also
    more arid grasslands in western North America

Grasslands in North America
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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

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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

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
Mid grasses
Little Bluestem Sideoats grama
Porcupine Needlegrass
Short Grasses
Blue grama Hairy grama
Grass Adaptations to Semi-Arid Conditions and
  • 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
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Worn high crowned tooth - from horse
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More Grass Adaptations
  • wind pollination developed because when living in
    areas with frequent drought, insect pollinators
    would be scarce - also winds are normally strong
  • 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
  • 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 - 1.93 cm
    maximum in June - 11.66 cm with secondary
    maximum in September 10.92 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

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