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The Oak Openings is a 130 square mile region (Moseley) located in Lucas, Henry and Fulton Counties of Ohio. The region sustains a mosaic of black oak savanna, oak woodland and wet prairie communities that persist on a series of post glacial beach ridges and swales. This area has long been recognized by naturalists as one of Ohio’s preeminent natural regions because of its rich diversity of vegetation. The region harbors more rare species than any other of a similar size in the state and sustains two globally rare communities, oak savanna and wet prairie.

Historically the Oak Openings Region may have covered over 300 square miles, extending as far as neighboring Wood county in Ohio and Monroe and Wayne counties of Michigan. Although remnants of habitat do still exist in these outlying areas, conservationists focus primarily on the “Moseley” region. This is a portion of the original area identified by Edwin L. Moseley in his classic 1928 publication, “Flora of the Oak Openings”. At that time, and still today, this area represented the best preserved remnant of Oak Openings habitat in Northwest Ohio and Southeast Michigan.

Previous to European settlement the Oak Openings was a pocket of prairie and oak savanna surrounded by the forests of the Great Black Swamp. Early settlers, many whom had just traveled through the dense forests of this swamp, called the area “Oak Openings” for its most obvious characteristics. Black and white oaks were the dominant trees and the landscape was very open and free of underbrush. Naturalist Lou Campbell describes what many settlers must have seen: “A short distance to the west (of Toledo) were hills of sand upon which only oak trees grew, and so sparse were the trees (that) a wagon could be driven in any direction through the patches of forest without the need of hewing a path.”

The Oak Openings is entirely confined to the physiographic region known as the lakeplain, a generally flat plain formed under the influence of post glacial lakes. The region is part of a sand belt that extends for approximately 120 miles from northeast of Napoleon, Ohio to west of Detroit, Michigan. The sand was deposited approximately 12,700 years ago as a series of beach ridges formed by post glacial Lakes Warren I, II, and III (Forsyth).

These ridges, in some areas 50 feet deep, were deposited over a surface of clay-rich glacial till. In the swales, or depressions between the beach ridges, the sand is thinnest and the till is close to the surface. The rapid permeability and instability of the sandy soils discouraged the development of natural surface drainage. This combined with the impermeability of the underlying glacial till maintained a high water table throughout the year. During late winter and spring, groundwater levels in the swales would often be above the surface, with depths of several feet not uncommon. In late summer and fall, levels would drop and the swales would dry. This extreme oscillation favored herbaceous vegetation, kept the growth of trees and shrubs in the swales to a minimum, and encouraged the establishment of the wet prairies.

Fire and the dry sandy soils of the ridges were the two primary process involved in maintaining the oak savannas. Savannas and woodlands experienced periodic fires that promoted a balance between the growth of trees and shrubs and herbaceous prairie/savanna vegetation. In general, the fire favored the growth of the herbaceous vegetation and inhibited the success of the woody plants. Trees remained part of the vegetative structure in these uplands not only because of the better drainage, but also likely as a result of a variable fire frequency, weather conditions and soils. The wet prairies, although primarily influenced by groundwater, were likely effected by fire as well.

Settlement of the region by Europeans in the early 1800’s, brought dramatic changes to the natural system. Logging removed the old growth trees and grazing impacted much of the herbaceous layer. Farming converted large areas of the land to agriculture. Ditches were installed to improve drainage and these lowered the groundwater in the wet prairies increasing the growth of woody vegetation. Fire suppression resulted in a rapid increase in woody growth within the savanna and very likely within the wet prairies as well.

Much of the oak savanna and oak woodland that has survived has become heavily shaded oak woods or maple/oak woods. These areas possess little of the herbaceous prairie understory they once had. Leaf litter and duff accumulation has increased significantly providing conditions suitable for more mesic, fire intolerant, species. What has survived of the wet prairie persists in relatively small pockets surrounded and fragmented by thickets of trees and shrubs.

Attempts to conserve habitat in the region have been ongoing since the 1930’s. The results of these efforts can be seen in a series of “core” conservation areas that occur sporadically throughout the region. The Toledo Metroparks maintain several areas with the largest and most significant being the 3600 acre Oak Openings Preserve Metropark. The Ohio Department of Natural Resources owns and manages three sites. Irwin Prairie (215 acres) and Lou Campbell (170 acres) State Nature Preserves and the 3100 acre Maumee State Forest. The Nature Conservancy owns and manages the 575 acre Kitty Todd Preserve. Some of these sites are being increased in size through the purchase of inholdings and small additions. The Nature Conservancy plans to enlarge its preserve, as tracts become available.

The stewardship, or management, of these protected lands is a critical component in efforts to preserve the biological significance of the area for the long term. Natural processes like fire and high groundwater must be reintroduced or supplemented with other techniques. Most areas are managed for the perpetuation of rare species and communities. Management efforts need to be expanded not only on protected sites but on private lands as well.

The Oak Openings Region, although modified and significantly reduced in size, persists as one of the few ecosystem scale oak savanna/prairie landscapes left in the midwest. High quality examples of black oak savanna and wet prairie exist on both public and private land throughout much of the region. Today however a new threat, urbanization from Toledo and its suburbs, threatens to ultimately destroy much of the habitat that remains.

Seven primary stresses have been identified for the Oak Openings Region. In order of significance they are loss of habitat, fragmentation of habitat, woody plant succession, groundwater lowering, exotic plant species and elimination of species.

The most significant of these stresses are the loss and fragmentation of habitat and several strategies have been developed to address them. Conservation efforts include land acquisition; increased community awareness concerning the significance and value of the area; compatible land use practices; promote the planting of native species available through local retailers; implement private and public land registry designed to encourage landowners to protect habitat on their own lands; encourage the formation of an Oak Openings grassroots organization that will promote conservation within the region.