Changes in a Restored Wetland during 18 Years of Management (Ohio)

In 1991, the Hamilton County Park District began restoration of a wetland area at Miami Whitewater Forest west of New Haven, where the Whitewater Shaker Community used to be. Land survey records indicate that the area in question once contained wetland and prairie habitat. After European settlement, the wetland was drained for agricultural use. In order to restore the area to wetland, the park district used a backhoe to locate and break drain tiles and a bulldozer to recontour the terrain, including construction of some dikes (Klein 1992). Thanks to water from natural springs and precipitation, the area became a 50-hectare ephemeral wetland. This area, which contains standing water during winter and spring, is known as the Shaker Trace Wetlands.

Around the same time as this restoration, the Hamilton County Park District established the Shaker Trace Seed Nursery from wild plants growing in relic prairie and wetland plant communities within 160 km of the nursery. Plants and seeds produced in the nursery were planted in parts of the Shaker Trace Wetlands and more than 120 hectares of planted prairie that surround the wetland area. Part of the wetlands was left unplanted to determine whether the wetland could become revegetated naturally without being planted. Here we share our observations of the plant community dynamics over two decades.

A vascular plant survey in the wetland/prairie complex was conducted from 1992 to 1996 via weekly visits during the growing season (early March through October) and monthly visits from November to February. Most species were identified in the field, but specimens of some plants were collected for closer examination with a dissecting microscope. Plants were identified mainly using Gleason and Cronquist (1991) and Holmgren (1998), and some specimens were deposited in the herbarium at the University of Cincinnati.

Figure 1.

Hydro-Axe operation to clear woody vegetation in Shaker Trace Wetlands in Ohio: a) resulting tire rut—such depressions hold water for longer periods into the dry season than do the surrounding areas; b) willows resprouting afterward, now being controlled by bush-hogging during the dry season. Photos by Denis Conover

During that survey, 527 species in 84 plant families were identified in the wetlands/prairie complex (Conover 1996). Approximately 23% of these species were planted. Species that were not planted presumably came from propagules in the soil seed bank and from natural vectors of seed dispersal. The wetlands attract large numbers of waterfowl and other wildlife such as turtles that may introduce plant propagules to the area. Some of the species that quickly appeared in wet areas without being planted were sedges (Carex spp.), spike rushes (Eleocharis spp.), rushes (Juncus spp.), water pimpernel (Samolus valerandi), clammy hedge hyssop (Gratiola neglecta), false pimpernel (Lindernia dubia), cattails (Typha spp.), arrowhead (Sagittaria latifolia), five-angled dodder (Cuscuta pentagona), and bulrushes (Schoenoplectus spp.), including the rare state-listed Pursh’s bulrush (S. purshianus), just one of several rare plant species that have spontaneously appeared in the wetlands. At the end of the 1992–1996 survey, we concluded that the wetland would become vegetated on its own, but that diversity could be increased by planting additional species (Conover and Klein 1994).

Figure 2.

State-endangered upright burhead (Echinodorus berteroi) appeared in tire rut depressions after the Hydro-Axe operation to control woody vegetation in Shaker Trace Wetlands in Ohio. Photo by Denis Conover

The prairie areas surrounding the wetlands have been maintained over the years by mowing and periodic prescribed burning to restrict tree growth. Mowing and burning of the wetlands was not always possible during extremely wet years. As a result, much of the wetland area had changed and become dominated by willows (Salix spp.) and cattails. In October 2006, the park district removed much of the woody vegetation from the wetlands by using a Hydro-Axe machine to cut down willows, other small trees, and cattails and thus opened extensive areas to more light. The large tires of the Hydro-Axe machine also churned up soil in the wetlands and left...