Experimental
Management Practices

Disturbances and Science II Prairie

Fire is a natural disturbance process in a prairie ecosystem and helps to discourage woody plants and exotics. Burning helps to recycle nutrients and stimulate above ground biomass, and fire is needed for the germination of some prairie seeds. A two-year burn cycle was initially planned for the prairie, with burns occurring in April or early May each year on alternate sides of the walk that goes through the prairie. The burns were usually conducted on a Saturday when the parking lots on each sode of the prairie were vacated. Intake fans on air circulation systems in the surrounding buildings were shut off, and the Ames fire department and campus security were notified. A large crowd of students and a few faculty, equipped with portable water tanks, hoses, and rakes would surround the perimeter of the section to be burned and the fire was lit. The fire created its own windstorm and flames leaped as high as the second story windows of Science II. The fire was usually over in about 15 or 20 minutes.

After the first few years, burning became irregular due partly to students leaving campus earlier due to the change in the University calandar and the ending of spring term in early May rather than June. No records are available as to when the prairie was last burned before 1990.

Woody species have been controlled periodically over the years by cutting and applying a herbicide to the cut stems. A small cottonwood tree was removed from the east side of the prairie in the early 1980's.

For several years after the original planting of the prairie, the eastern half was infested with a large and dense stand of yellow sweet clover (Melilotus officinalis). This plant is a biannual and so only appeared every two years. It has not been a problem in recent years but still persists.

Soon after the prairie was planted, the soil was disturbed within a strip about 2-3 meters wide running next to the south and west walls of Science II. Giant ragweed quickly colonized this strip and shaded out the growth of other plants for several years thereafter. The ragweed, an anual, was eventually controlled by cutting the plants before they produced seed. Several attempts have been made to reseed this strip with native grasses but success has been limited. Presently, field bindweed is prevalent on parts of this formerly disturbed area.

Another serious disturbance occurred in the late 1980's when the University laid new telecommunications lines along the walk next to Science I. The vegetation was removed on a strip about 2 meters wide along the entire south edge of the prairie and a trench was dug to a depth of about 0.5 meter. The year after this disturbance reed canary grass appeared and it is suspected that the seed was planted by contractors.

Experimental Management Methods: 1995

According to the plant inventory, the Science II Prairie still retains many of the species that were originally planted, some species have disappeared, and new species have been introduced. In addition many alien species have invaded the prairie (Table 1). The restoration ecology class initiated several experimental management practices in the Fall of 1995. These practices will compare burning with mowing as a technique to recycle nutrients and restore plant vigor, control non-native invasive species, and increase species diversity.

An employee from the Department of Facilities Planning and Management mowed the Science II Prairie with a large flail mower on 20 October 1995. The prairie was mowed prior to an experimental burn to give the burn crew more control over the fire. No rain had fallen for several days and the prairie was in favorable dry condition. The mowing left a layer of dry mulched vegetation that was ideal for burning.

The prairie was then divided into 8x8 m or smaller quadrats and marked with 3/8 in steel rods. Fire breaks were created by saturating the ground and mulch with water along a 2 m wide strip on either side of two 8 m wide, north-south rows. These two strips were burned mid-morning on 21 October 1995 (Fig.6). It was a cold, morning with moderately strong winds between 15 and 20 mph. The experimental burn was conducted by the Restoration Ecology Class and other volunteers consisting of members of the Fish & Wildlife Biology Club and faculty.

Seed Source Part of the prairie was seeded on 18 November 1995 with a mixture of native prairie seeds purchased from Carl and Linda Kurtz, St. Anthony, Iowa. These seeds were harvested from a 7-year old restored prairie on their farm in October 1995. Seed was applied to three alternate 8-meter wide rows that were perpendicular to the burn treatment (Fig. 6). A fertilizer spreader was used as a seed dispenser and was followed by handseeding. The seed was lightly raked to ensure its contact with the soil surface. The burning and seeding of Science II prairie created a checkerboard design of blocks of varying size that received one of four different treatments: 1) no treatment (control), 2) burn, 3) seed, and 4) seed and burn.

Treatment effects will be determined by monitoring the appearance of new species on plots, changes in the distribution and dominance of selected species, and reduction in the number of alien species.

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