Loess Hills State Forest

Interest in forming a Loess Hills State Forest had been expressed for some time prior to its being recommended in the Iowa Conservation Commission’s 1985 Forest Resources Plan. When the State Lottery became a reality, acquisition of the forest became possible. First lands were acquired in June, 1986 with purchase of the Bothwell and Hrabik properties. Prior to the start of acquisition, the area was a mixture of private ownership. Mid America Council of the Boy Scouts of America was one of the largest land holders in the area with 1840 acres. Average size of acquisitions through June of 2007 was 143 acres and they ranged from 3 to 1037 acres.

The first acquisition was made in 1986 using LAWCON and Lottery funds. Since Resource Enhancement and Protection, (REAP) funds became available in 1987, approximately $400,000 of the annual land acquisition account for IDNR has been used for the forest. As of July 2007, 7.8 million dollars have been used for acquisition from REAP, Lawcon and Legacy monies.

Land is acquired only from willing sellers. An average of 563 acres has been purchased each year. The largest acquisition was the Rice property, 1037 acres in the Preparation Canyon Unit, purchased in May 1993.

In September 1989, the city of Pisgah donated a 3 acre lot to be used as the site of the forest headquarters. A combination office/equipment storage building was completed in July, 1993, at which time Governor Branstad, other officials and local citizens held an open house to observe completion of the building. A visitors center was completed in October 1999 at which time Governor Vilsack, other officials and local citizens held an open house. The center is open on the weekends from 1-4pm by local volunteers from April thru October. The center is also used throughout the year for meetings and travelers visiting and learning about the Loess Hills from the displays.

The Loess Hills of western Iowa were formed from 20,000 to 10,000 years ago of finely ground windblown silt from the glacial deposits. As the Pleistocene glaciers melted, the Missouri Valley became a major channel for tremendous amounts of water. Each winter season, as the quantity of melt water was reduced, large areas of flood-deposited sediments were left exposed to the wind. Silt, clay and fine sand were lifted by the wind, carried to the east and deposited. The bedrock of Harrison and Monona Counties is limestone upon which lies a mantle of drift, sand, gravel, loess, and alluvium. It determines most of the surface features in the counties today.

Three layers of loess have been deposited in the Loess Hills--Loveland, Post-Kansan and Post-Iowan. The Loveland Loess is a water deposit formed during the melting of the Kansan Glacier. It is a compact, heavy, reddish clay which is very sticky when wet. It is highly valuable in the dry hills because of its ability to retain moisture.

The Post-Kansan Loess is fine and compact and light blue in color. It takes up moisture slowly when wet but retains it relatively well.

The Post-Iowan Loess is the immediate subsoil of the upland regions of the hills. It can occur up to 90 feet in depth, deeper closer to the Missouri River. It breaks vertically into irregular columns causing frequent slippage and faulting at the surface.

The thickness of the loess and differences between the soils formed in the loess are related to the distance from the source of the loess. The loess is the thickest in the bluffs, reaching more than 200 feet deep in some areas. In places, mainly on steep hillsides adjacent to stream valleys, the Wisconsin loess has been removed by geologic erosion. Here, glacial till, or in a few places the Loveland Loess deposit is exposed on the surface.

The Loess Hills are an outstanding example of two basic geologic processes the strong influence of past eolian or wind deposition as well as erosional sculpture of the land. These origins contribute to potential environmental hazards of slope failure and collapse. In addition, the association of the loess, the topography, and the vegetation combine for a classic display of the interdependence between geology and ecology. In this high relief area, the terrain supports a mosaic of unique ecological niches.

The soils of the Loess Hills State Forest were formed in loess, alluvium, and glacial till; most soil series formed in a loess parent material . Loess is yellowish-brown, wind-deposited material consisting largely of silt particles. This specific soil forming factor is what gives Iowa's Western Loess Hills their name as well as their peculiar form. The steep bluffs, comprised solely of loess soil, rise to between 150 and 250 feet above the Missouri River bottom land. The native vegetation of these soils was almost exclusively prairie grasses, with some timber along streams and drainage ways.

The steep, ridged topography, combined with the special physical properties of loess, create some problems in the Loess Hills. The angles of the slopes often range from 50 to 75 degrees; this is due to the geo-technical or engineering properties of the soil. The loess, composed primarily of coarse silt particles, has a very low shear strength when water-saturated, so that often it cannot bear its own weight. However, when relatively dry, the loess develops a greater apparent cohesion; this allows the loess to maintain the spectacularly bold bluffs and ridges-forms along the Missouri River valley. These special soil properties impose some serious limitations on any development involving roads and buildings.

Loess is easily eroded by running water. This factor, combined with its collapsibility, contributes to another major problem -- soil erosion and resultant gullying. Some of the highest soil erosion rates in the nation, averaging about 40 tons per acre per year, have been documented in this region. The resulting high sediment loads in local streams necessitates continual maintenance of drainage ditches and stream channels and results in detrimental conditions for many aquatic species.

The Loess Hills State Forest is made up of six general soil associations that are located in Harrison County and five general soil associations that are in Monona County. The Nine different soil associations of the two counties are the Sarpy-Albaton-Carr, Albaton-Haynie-Onawa, Luton-Keg, Kennebec-McPaul-Nodaway, Hamburg-Ida-Monona, Monona-Ida-Napier, Luton-Salix-Blencoe-McPual, Kennebec-Zook-Mcpaul, and the Hamburg-Ida-Castana-Napier.

The climate in the Loess Hills is of the continental type, characterized by wide variations and rapid changes in temperature. Snow cover of nearly an inch is common for about 47 days per winter. Winter conditions are often mild with temperatures ranging from 20 to 25 degrees Fahrenheit, with occasional sub zero temperatures. During the spring, average temperatures range from 45 to 75 degrees Fahrenheit. The average monthly rainfall during the spring reaches nearly 4.6 inches. The extent of precipitation is enough to cause erosion in the loess as well as damage to facilities. The last spring freeze usually occurs about May 1, and the first fall freeze occurs about September 6.

The growing season is about 160 days. Summer temperatures average between 71 and 76 degrees Fahrenheit with some high-temperature extremes above 100 degrees Fahrenheit. These high temperatures along the ridges and south facing slopes create an environment which is dry enough that only adapted vegetation can survive and grow.

The average total precipitation for the entire year is about 31 inches.

The predominant plant communities on the forest are prairie, savannas, and hardwood stands that contain species like bur oak, red oak, black walnut, hickories, basswood, elms, ashes, Kentucky coffee tree, cottonwood, ironwood, and red cedar. If one species was to be singled out as typical it would be bur oak due to its ability to grow on dry sites and withstand fire. Black walnut is the most important and valuable commercial species. The forest contains many areas of natural prairie comprised of big and little bluestem, Indiangrass, sideoats grama, and forbs such as yucca, pasque flower, and lead plant. Some prairie ridges are very diverse with 100-350 different species. 

About 800 acres have been planted to red oak, black walnut, bur oak, green ash, white ash, poplar, shrubs, and pine.

About 400 acres of native grasses and local ecotype seed have been planted.

The Loess Hills of western Iowa exhibit a unique diversity and abundance of wildlife species. The Hills, once home to black bear, elk, buffalo, antelope, and wolves now support populations of smaller animals. This change which occurred with the change in land cover since settlement when the Loess Hills were transformed into a diversity of vegetative cover and wildlife. Both fire control and agriculture have played important roles in this transformation.

The advance of woodlands and agriculture have confined prairie communities to narrow ridges and steep hillsides. On the other hand, forests and agriculture brought with them new and varied species of wildlife. Species such as prairie chicken, prairie rattlesnake, and plains pocket mouse have decreased while white-tail deer, raccoon, quail, pheasant, and wild turkey have flourished. This trend has led to a concern for the protection of endangered and/or rare species and their associated habitats.

The forest is named after the geological formation that reaches its fullest development only in western Iowa and in China. The Loess Hills are a unique formation and their existence and the fact that they have become vegetated with forest species in recent years played a role in the decision to develop a state forest in this area.

Three of the Units, Mondamin, Pisgah and Little Sioux are named for towns in the vicinity. The Preparation Canyon Unit is named after a small settlement, no longer in existence, of Mormon travelers who split off of the Salt Lake City migration.

The Gifford Unit, located near Council Bluffs, is a forty acre tract of timber on the Missouri River flood plain given to the state by the late Dr. Gifford. The Gifford unit is not properly a part of Loess Hills Forest, but is managed as an administrative unit of the forest.

The Loess Hills State Forest is managed in accordance with the IDNR Forest Ecosystem Management Guide. The woodlands are managed for several benefits including production of wood products, wildlife, quality water, recreation, and protection of plant and animal communities.

Each of the units also have areas of savanna where trees and prairies are managed together. These have been demonstration areas featuring fire and other management tools. Savannas occurred in the area in pre-European settlement times.

Prairies were common components in the Loess Hills landscape in pre-European settlement. About 2,200 acres of prairie ridges and seedings are being managed with fire on 2-5 year burn rotations. There are over 2,500 acres of prairie, woodlands and savannas burned annually on the forest throughout the four seasons. Additional work is also done to remove and manage red cedar and other woody vegetation from the prairies.