• Grasslands are ecosystems in temperate continental interiors where precipitation is too low to support trees but not so dry to become desert.

These ecosystems include

• Steppes in central Asia

• Pampas in Argentina

• Savannas in East Africa

• Prairies in North America

The deep roots of grasses contribute to a fertile soil well suited for crops in the grass family such as wheat, barley, oats, rye and corn.

• Ecology is the study of organisms in all their complex interactions with the environment.

These interactions can be divided into hierarchical levels of organization:

• Organism: an individual living thing.

• Population: a group of organisms of the same species in one area.

• Community: many species interacting in the same area.

• Ecosystem: living (biotic) organisms and the nonliving (abiotic) material they interact with.

• Biome: ecosystems composed of similar communities around the globe.

• Prairies once dominated the landscape in North America, supporting wildlife such as the plains bison.

Stretching from Alberta, Saskatchewan, and Manitoba all the way south to Texas, prairies covered an area of 1 million square miles of the Great Plains.

To the north, shrublands such as the Peace River Parkland form a transition to the boreal forests of upper Canada.

On the east, tall grasses grade into eastern deciduous forests in the Prairie-and-Oak Transition Zone.

• Large herds of bison roamed the vast Great Plains grasslands.

Francisco Vasquez de Coronado described the land in 1541:

• I found such a quantity of [bison] that it is impossible to number them, for while I was journeying through these plains, until I returned to where I first found them, there was not a day that I lost sight of them.

Captain Meriwether Lewis wrote from the Dakota plains in 1804:

• I do not think I exaggerate, when I estimate the number of Buffaloe which could be comprehended at one view to amount to 3000.

Estimates of bison populations ranged from 12 to 125 million. Settlement by Europeans in the mid-19th century quickly wiped them out - the last free-roaming bison was killed in 1891.

• The Great Plains lies to the west of the Coast Ranges and Cascades-Sierra Nevada mountain ranges along the Pacific coast, and the Rocky Mountains further inland.

These mountains block moisture carried from the Pacific Ocean by the prevailing winds (westerlies), creating a rain shadow with a semi-arid climate that favors grasses.

• The rotation of the earth yields prevailing winds called westerlies in North America.
Moist westerlies from the Pacific Ocean rise when they encounter the Sierra Nevada, depositing precipitation on the windward side. The dry air then descends the leeward side, casting a rain shadow of arid climate where deserts such as the Mojave Desert are often found.
Review:

• The Great Plains grasslands can be classified into 15 ecoregions of 4 types:

• Short Grasslands: Fescue, June Grass

• Mixed Grasslands: Blue Grama, Buffalo Grass

• Tall Grasslands: Big Bluestem, Indian Grass

• Woodlands and Savannas: Oak, Dogwood

When Pierre François-Xavier de Chevalier crossed southern Wisconsin in 1761 he noted:

The grass is so very high that a man is lost amongst it.

Much of these grasslands (between 15% to 99.9%) have been converted to cultivation for farming or ranching.

• Weathering of parent material (rock) erodes chunks of minerals.

• Physical forces such as wind and water can break the rock into smaller particles.

• Chemical reactions can alter the composition of parent material.

• Biological processes from living organisms can also produce soil through physical or chemical means.

Large chunks called gravel eventually erode into smaller sizes to start the formation of soil.

• Soil types

As rock weathers, the particles are called sand, silt, and clay as they become progressively smaller.

Soil can be classified into various types according to the mix of these 3 particles.

In general, sandy soil is loose and drains water quickly; clay soils are compacted and poorly drained.

Loamy soils have a relatively balanced proportion of different particle sizes; most plants are adapted to these types of soil.

• A reconstruction of the extent of prairies in Illinois as of 1820 shows that the "prairie state" was indeed once covered with prairie grasses, grading into deciduous forests along streams.

Today, less than 1% of 1% of true tallgrass prairie remains.