Nebraska Center for Writers

fromTHIS FRAGILE LAND
by Paul A Johnsgard

THE SOILS OF NEBRASKA are foreign. They came originally from silty sediments of rivers draining the eastward-facing ranges of the ancestral Rocky Mountains. These sediments were later extracted from the surface layers of Tertiary and Pleistocene deposits and wind-carried up to several hundred kilometers, probably during dry and windy interglacial periods. They drifted mostly eastward and southward, to be deposited blanketlike over much of southeastern nebrsaska and parts of northern Kansas and extreme western Iowa. They are now mainly to be found between the Sandhills and the lower lands lying somewhat farther east toward the Missouri Valley, where later glacial till subsequently covered or variably replaced them, obscuring their windy origins. In some places in eastern Nebraska and in the loess hills of extreme western Iowa, this silty blanket extends to a depth of as much as 50 meters. Water is readily able to penetrate such uniformly sized substrate materials, and the calcium-rich soils that have developed above them are not only very uniform in texture but also relatively low in organic matter.
Over time, wind and water erosion in the loess hills region have produced a pattern of gently undulating valleys, hills, and small bluffs. The steeper slopes of the hills and bluffs often take the form of small but nearly vertical-walled canyons, with many vertical cleavage fissures in the soft loess substrate. Along these cleavages the loess tends to break and slide doward repeatedly, eventually producing a distinctive "cat-step" erosion pattern that resembles a series of natural, nearly hoizonatal terraces or steps. Overgrazing by large mammals can easily aggravate these erosive effects.
This region, traditionally described geographically as the Loess Hills and Plains (or Rolling Hills and Dissected Plains) of Nebraska, covers several thousand square kilometers of the state and is roughly bisected by the Platte River. A general geographic transition area between the shortgrass plains and sandhills to the west and the Missouri Valley to the east, it is also a botanical transition area. Although the native vegetation of the loess hills is largely mixed-grass prairie, some local areas are dominated by short grasses, and others — usually on north-facing slopes and on lowlands — approach typical tallgrass prairie. These more mesic sites, like the tallgrass prairies to the east, were among the first to be plowed and converted to dry-land farming. Many of the other areas of the Loess Hills are still only marginal for nonirrigated crop growing but provide important rangeland resources for regional farmers and ranchers.

Reprinted with permission
from This Fragile Land
Copyright © 19
by Paul A Johnsgard


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