Transcript sod (or turf)

Illinois Plant Communities –
Prairie Ecosystems
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, switchgrass 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 - 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 .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 tillers
Spread 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; 176.7 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 grama
Common 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 Sparrow
Unaffected by grazing
Bobolink
Decline with grazing
Prairie Vole
Short-tailed shrew
Unaffected by grazing
Thirteen-lined ground squirrel
White-footed deer mouse