The Formation of the Tallgrass Prairie

A most perplexing question

Objectives

• To be able to identify and describe aspects of the tallgrass prairie formative history.

• To prepare for our field trip to the UNI Tallgrass Prairie Center.

A Puzzle

• After all of these years, we are still wondering about the forces that created the tallgrass prairie.– At one point there were a dozen reasons listed in

scientific journals.– One of the original answers was that prairie soils are

infertile to grow trees.• Report of James Monroe to Jefferson describing the

tallgrass Prairie “A great part of the territory is miserably poor . . . and will not have a single bush on them for ages.”

A Puzzle

• Another theory was that the tallgrass prairie had developed in the absence of coarse soil material (the rocky terrain found “out east”).– Plenty of tallgrass prairie is found on rough rocky

ground.• Some blame the bison for trampling and grazing.– Railroad promoters promised eastern farmers that

the grasslands we become “elysian” once the Indians and bison were gone.

A Puzzle

• “. . . into the late 1860s and early 1870s very large herds still roamed the northern plains. For example, in 1867, the Captain of the steamer Stockdale, on the upper Missouri River, reported that the progress of his boat was “ . . . held up while a herd of snorting and bellowing shaggies crossed the stream” (Gard 1956:35). The bison herd was so large that the Stockdale could not move for several hours. The Captain had to shut down the boat’s paddle wheel because bison were becoming entangled in it.”

A Puzzle

• Fire – the prairies are fire ecosystems, though how often did the fires happen naturally.

• There are no “pat” answers or at least we haven’t found one. – My personal feeling is that the endurance of the

tallgrass prairie is due to their deep an resilient root systems – grabbing the soil to a startling depth and then refusing to let go.

Born Out of Ice

• The heart of the tallgrass prairie’s territory was a product of ice.– Mile-thick rivers of ice flowed down from the north,

grinding and tearing the earth (producing fine soils from rock).

• There were four major ice sheets:– The Nebraskan, Kansan, Illinoisan, and Wisconsin. – They began less than a million years ago (recent in

geological time) and lasted up until 13,000 year ago (ebbing and flowing over the Midwest and plains).

Extents of Wisconsin and Illinoisan Glaciation

Born Out of Ice

• Approximately 70% of the original tallgrass prairie was formed on deposits created by glacial ice. – The ice seemed to create a soil, laden with

minerals, that was ideally suited to nurture the tallgrass prairie and its richness.

• However, there are/were plenty of tallgrass prairie lands that were never glaciated (ex. Flint Hills of Kansas).