O'Hara Woods

Description

O'Hara Woods is a natural prairie grove containing undisturbed mesic upland forest and savanna once typical of the Northeastern Morainal Natural Division. Protected from prairie fires in presettlement times by wet soil and a steep ravine, the grove appeared as an island of trees in the midst of a vast prairie and marsh sea. Today, the woods is surrounded by crop fields. It is one of the last undisturbed maple prairie groves remaining in northeastern Illinois. The complex biological cycles of the forest soils are a key feature of the woods. The soil is rich in arthropods, earthworms, fungi and other decomposers which actively turn leaf litter into nutrients. These nutrients are then cycled upwards into nearby trees. The speed and vigor of this process are good indications of the overall health of the forest. A stand of bur oak, hawthorn, and white ash with a brushy understory is found southwest of the ravine and indicates that this area was previously a savanna. Northeast of the ravine and in the ravine itself a rich mesic forest can be found. Here the dominant species are sugar maple, basswood, red oak, blue ash, and walnut. And, a floodplain near the outer edge of the grove provides good conditions for bur oaks. Spring flora of the forest floor include species such as broad-leaved puccoon, squirrel corn, blue-eyed mary and bluebells. Fire pink is present in the summer. Seepage areas along the base of the slopes support skunk cabbage and marsh marigold, and a remnant of the once-vast Lily Cache Slough is present at the northern edge of the woods. Typical vertebrate species such as deer, raccoon, red fox, great horned owl, song birds, and migrant waterfowl may also be seen. O'Hara Woods has been lightly grazed and timbered since presettlement times and was used for storage of dynamite during World War II; twelve concrete foundations and several roads still remain.