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Tall Grass Prairie

Grassland is the largest of the four major natual vegetation formations that covers the earths land surface
by

Todd Golder

on 19 August 2012

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Transcript of Tall Grass Prairie

Tall Grass Vegetation Communities
PNV 66-Bluestem "True Prairie"
PNV 67-Nebraska Sandhills Prairie
PNV 68- Blackland Prairie
PNV 72- Oak Savanna
PNV 73-Bluestem Prairie and the Oak Hickory Forest
PNV 75- Cross Timbers
Andropogon gerardii
Panicum virgatum
Sorgastrum nutans
Sorghastrum nutans
Panicum virgatum
Andropogon gerardii
North Dakota and Minnesota southward to Oklahoma
Dominated the lowlands
Grows in large clumps, rhizomatous
Nutritious to livestock and wildlife
Switchgrass
Big Bluestem
Western edge in low moist areas
Eastern edge near forest ecotones
Sod forming, growing in dense colonies
3-6 feet tall
Indian grass
Throughout prairie
Favors mesic conditions
2-6 feet tall
Short scaly rhizomes
Highly nutritious
Dense vegetation of tall grasses
Many perennial forbs
Climate
The most mesic of the grasslands of the US Central Plains
Has a diverse N-S gradient in precipitation
More precipitation in the south
75% comes during summer growing season with summer drought becoming periodic
Fire was influential under pristine conditions
Burn frequency every 3 to 5 years
Lightning strikes
Tall Grass Prairie
Soils
Are primarly Mollisols
Grading into Alfisols along forest edges or in seasonal mosaic
Natural Disturbance Vector: Fire
Topography described as flat to rolling hills of grass
Remnant Area:
Flint Hills, Kansas
Osage Hills, Oklahoma
Sand Hills, Nebraska
Disturbance Vector- Native Wildlife
Native tall grass species have a high resistants to grazing pressure
Evolved under wild ungulate by the grazing of bison
Only about 1 to 2% left
Minnesota 75,000-100,000
Iowa 10,000 acres
Missouri 70,000
South Dakota 50,000
Indiana 200-400
Nebraska and Southern South Dakota
Calamovilfa longifolia
Prairie Sandreed
Medium dense to open grasslands
Changes are generally less marked
Fragile sandy soils susceptible to wind erosion
Watershed, wildlife and domestic grazing are the primary use.
and Andropogon gerardii
Grows throughout summer
Produces from seed and rhizomes
Drought tolerant and increases during drought
Fair forage to cattle and wildlife
Nebraska Sandhills
Bluestem Prairie
Blackland Prairie
Located in Texas and South Oklahoma
This ecoregion is ideally suited to crop agriculture.
This has led to most of the Blackland Prairie ecosystem being converted to crop production
Vertisol soils, rather than Mollisols
Schizachyrium scoparium
Little Bluestem
Dominating the upland, open woods and dry hills
Good for all livestock when immature
1 to 3 feet tall
Bunchgrass with clumps
Grades into the mixed grass prairie
Bouteloua curtipendula
Sideoats grama
Reproduces by seeds, tillers and rhizomes
The small oat-like seeds develop on the side of the stalk.
Good for all classes of livestock and wildlife throughout summer and fall
Oak Savanna
Located in Wisconsin, North Dakota and Minnesota
Tall grass prairie with broadleaf decidious trees scattered or in groves
Burr Oak
Quercus macrocarpa
Often found near waterways in more forested areas, where there is a break in the canopy.
It is also a fire-resistant tree, and possesses significant drought resistance by virtue of a long taproot.
New trees, after two to three years of growth, may have a 1–2 m deep taproot.
Bluestem Prairie and Oak Hickory Forest
Cross Timbers
Texas to Kansas
The woodland and savanna portions of the Cross Timbers are mainly post oak and blackjack oak on coarse, sandy soils
fire suppression in recent years has increased forest density and allowed Eastern redcedar to invade as well.
The short, stout oaks that grow in the Cross Timbers were no good for timber and those that were not cleared for farmland constitute one of the least disturbed forest types in the eastern United
Black Jack Oak
Quercus marilandica
Post Oak
Quercus stellata
The Blackjack Oak is small compared to other oaks.
Its thick, black bark is deeply divided into rough, nearly square plates.
The name refers to the use of the wood of this tree for fence posts. Its wood, like that of the other white oaks, is hard, tough and rot-resistant.
Primary forbs include
Lead Plant
Amorpha canescens
Found on drier sandy soils and rocky open woodlands
1 to 3 feet tall
Historically, fire supressed the encroachment of trees and shrubs
Reduced competition from cool season invaders such as Poa pratensis and Bromus inermis
Improves the palatability and nutritional value of the forage
Overgrazing Impacts
Livestock select the most palatable species when grazing
With overgrazing, Panicum virgatum and Sorghastrum nutans decline first
Followed by Schizachyrium scoparium
Andropogon gerardii tends to persist with overgrazing, possibly because of its short strong rhizomes
Bouteloua curtipendula and B. gracilis become more abundant as the tall grass declines
Buchloe dactyloides increases in overgrazed prairies by as much as 70%
Overgrazing Effects
Increase in Nassella leucotricha (Texas wintergrass) and Buchloe dactyloides (Buffalo grass)
Increase in annual grasses
Overgrazing Effects
Decreases in S. scoparium, Hesperostipa comata (Needle and Thread) and A. gerardii
Increase in Bouteloua hirsuta, Calamovilfa longifolia and Sporobolus cryptandrus
Human Impacts
Agriculture
Unregulated development
Suppression and removal of natural disturbance vectors
Kuchler's PNV Designation
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