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Prairie Creek Savanna

Location: Will County
Size of area affected by MSCSF-funded work: 43 acres
Owner: Midewin National Tallgrass Prairie, U.S. Department of Agriculture Forest Service
Partners: U.S. Department of Agriculture Forest Service, USACE, CorLands

Action: Cutting and removing trees and brush, follow-up treatment of woody resprouts and seedlings, control of invasive herbaceous plants, and hydrologic monitoring both before and after the removal of woody invasives.

Summary: Awe-inspiring oaks and soaring hickories are found at the Prairie Creek Savanna. But buckthorn, honeysuckle, and back locust had choked out almost all attempts of oak or hickory seedlings to find the sun, and there was little regeneration of these characteristic trees of the savanna. Also, the dense cover of woody invasives was preventing the growth of the native herbaceous species you would expect to find in a healthy savanna system.

Extensive cutting, hydro-axing, and select girdling of the locusts, buckthorn, honeysuckle, and other younger weedy trees has dramatically opened up Prairie Creek savanna. In addition, an aggressive scouting and treatment program for garlic mustard, buckthorn, honeysuckle, and multiflora rose was implemented. Wild geranium, mayapple and tall bellflower now bloom in the under story. A local nursery specializing in native trees supplied seven-foot tall young bur oak and shagbark hickory so there will be some intermediate growth in the savanna rather than just ancient trees and baby ones. They were planted sparingly, only one or two per acre. In addition, select herbaceous species were dormant seeded where groundcover recovery was slow. Midewin staff is now confident that there is adequate fuel for fire and the restoration’s first prescribed burn is scheduled for the spring of 2006.

An interesting component of work at this site is the hydrologic monitoring to measure the effect of woody invasives on soil moisture and water table levels. There's been a theory that one way to restore wetter conditions to a grassland or savanna is to remove the invasive woody vegetation. The idea behind it is that trees are much more efficient about the process of taking water from the soil through the roots, utilizing the water and then releasing it as vapor from the above-ground parts of the plant. If trees are taking large amounts of water from the soil, removing them could result in increased soil moisture.

Two weather stations were installed here to measure precise rainfall and other weather conditions existing on site that would affect the soil's water content. The site’s soils were mapped and classified to confirm if the site’s subsurface conditions were uniform. Soil moisture sensors and pedometers with data loggers were set out in transects. Data has been collected from areas for the season before cutting began. The removal of the woody invasives was then implemented in two phases (one monitoring transect in each phase) over successive winters, so that there was a summer where there was one transect in an area that had been cleared and one transect in an adjacent area that was uncut. Processing of the data indicated that the area where the woody invasives had been removed had statistically significant higher soil moisture and shallow water table levels than the area that had not yet been cleared of buckthorn, honeysuckle, black locust, and other weedy species.