Four basic ecosystems make up the Big Darby Creek Watershed: Stream, Wetland/Riparian Forest, Oak Savanna, Tallgrass Prairie and Bluff Prairie.
The Stream Ecosystem
Most streams throughout Ohio and their fish fauna have been greatly modified since settlement times. These modifications include the removal of
trees and brush along stream banks, ditching and draining of marshes, increased erosion of land and sedimentation and impacts caused by pollutants. These drastic modifications have considerably modified the general composition of Ohio’s fish fauna, changing it from a species complex dominated by fishes requiring clear or vegetated water to one dominated by those species tolerant of turbid water and of bottoms composed of clayey silts.
The relative absence of these types of modifications is what makes the Big Darby Creek system so special. The myriad fish species, which call the Darby Creeks home, require clear waters with aquatic vegetation, clean bottoms of sand, gravel, boulders, and bedrock. While aquatic environmental conditions in the Darby have deteriorated in this regard over the years, the Darby remains an island of aquatic biodiversity in a sea of severely impacted Ohio and Midwestern streams. In many ways, the Darby is a window back into the time before European settlement.
The Wetland/Riparian Forest Ecosystem
Serving as transition zones between dry land and water, wetlands are unique environments that prove both ecologically and economically valuable.
Wetlands filter out sediments, nutrients, and pollutants from surface runoff. They are valuable habitats for terrestrial and aquatic organisms, and provide resting or breeding areas for migratory birds. Also, wetlands help prevent or moderate flooding.
The Darby watershed, much like all of Ohio, has suffered a 90% to 95% decline in wetland acres. Today, most of the wetlands have been drained, especially in the headwaters where the stream itself was channelized to facilitate drainage. The few remaining wetlands in the watershed play a significant role in maintaining water quality.
The riparian forests, which once covered the watershed, had a significant influence over the aquatic ecosystem. Forested corridors are important
because they intercept sediment, nutrients, pesticides, and other materials in surface runoff and reduce nutrients and other pollutants in shallow subsurface water flow. Woody vegetation in forest buffers provides food and cover for wildlife, helps lower water temperatures by shading the water, and slows out-of-bank flooding. In addition, the vegetation closest to the stream provides organic nutrients important to aquatic organisms. Today, the forest has largely been replaced by agricultural land uses.
The Oak Savanna Ecosystem
An intact oak savanna in Ohio is a community of oaks and other less common tree species forming an incomplete canopy over an understory of prairie species, typically grasses. These plant communities are characterized by sparse (10-50%) canopies of bur oak (Quercus macrocarpa) and white oak (Quercus alba) with an herbaceous layer which includes mesic prairie species such as big bluestem (Andropogon gerardii), little bluestem (Schizachyrium scoparium) purple coneflower (Echinacea purpurea), prairie dock (Silphium terebinthinaceum), stiff goldenrod (Solidago rigida), gray-headed coneflower (Ratibida pinnata)and Indian grass (Sorghastrum nutans). Generally, these are areas with isolated groves of trees found on gently sloping to nearly flat terrain. Soils are typically moderately drained to well drained and deep. Natural processes important in the formation of Midwest oak savanna include fire, climate, topography, soil, and grazing by large herbivores. Where this occurs, oak savanna is typically viewed as a transitional community between forest and grassland.
The oak savannas and open oak woodlands of the Midwest are among the world’s most threatened communities. At one time, oak savannas may have covered some 27 to 32 million acres in the Midwest. By 1985, the number of relatively high-quality stands had been reduced to about 0.02 percent of the original amount. Most are highly degraded as a result of timber harvesting, overgrazing, agricultural use, fragmentation, and fire suppression. Thousands of acres of this oak savanna ecological community originally existed in the Big Darby Creek watershed. As in other areas throughout the Midwest, oak savannas in the Darby watershed have undergone a massive decline.
Restoration of oak savanna has been successful in central Ohio and other regions. Restoration specialists have found that when savanna remnants are actively managed, dormant seed banks can assist in reestablishment of both the understory and canopy layers of this community. Management on the approximately 18 acre privately owned W. Pearl King Savanna in Madison County, has been successful in maintaining one of the few remaining natural occurrences of oak savanna in central Ohio.
The values of maintaining this ecological community in the Darby watershed are many. Most savannas are small relics and historical remnants of a once common community that evolved in association with fire and grazing in the Darby plains. As such they serve as a natural seed source and potential targets for restoration. Although each surviving grove is typically small, the total acreage in the Darby watershed, while unknown, could be considerable.
Sources: Faber-Langendoen, D. (ed.) 1999. International Classification of Ecological Communities: Terrestrial Vegetation of the Midwestern United States, Ohio Portion. The Nature Conservancy, Midwest Conservation Science Department, Minneapolis, Minnesota. 109 pp. and appendices.
The Tallgrass Prairie Ecosystem
At the beginning of the nineteenth century, the tallgrass prairie was a major ecosystem occupying 240 million acres of mid-continent North America. By the end of the century, it was almost gone. Most of the tallgrass prairie was converted to agricultural use during the last 60 to 70 years of the nineteenth century. The early settlers of west central Ohio found large prairie openings in the forest – islands of grassland scattered across a dozen or more counties. These prairies, dominated by big bluestem, Indian grass, and little bluestem, were outliers of the vast prairie farther west.
In Ohio, wet and mesic tallgrass prairies occurred primarily in four main prairie regions, including the Darby Plains, which extend into the western portion of the Big Darby watershed. In the Darby Plains, because of the flat terrain and slow drainage, most of the prairies were covered with water for extended periods each year. At other times the prairies became very dry, and wild fire was almost an annual event.
These prairies, and accompanying soils, had developed over thousands of years since the continental glaciers had retreated from the area. However, as settlers learned how to drain and cultivate the prairie lands, the face of the landscape became changed so thoroughly that within a century almost all vestiges of the original wet prairies were obliterated.
Dr. Jeremiah Converse, a physician of Plain City and an 1848 graduate of Starling Medical College in Columbus, Ohio, described the prairies of Madison County (Brown, 1883:341-342) in this way:
This whole country was a sea of wild grass, and flowering herbs …There were many other varieties that grew upon the prairie besides those that were found skirting, and in the oak-openings; such as the daisies, buttercups, wild pink, coxcomb, lilies and many others equally beautiful. It was, indeed, a grand sight to a nature-loving mind, to look over these extensive prairie fields and behold them mantled with so luxuriant a growth of vegetation and decorated so lavishly with an almost endless variety of flowers, variegated with all the colors of the rainbow…
Today, only remnants of these habitats remain in the Darby Creek watershed. These valuable remnants provide unique opportunities and genetic material not only for restoration of wet prairie communities and ecosystems in the area, but also for restoration of human awareness of the natural heritage of the Darby Plains. Prairie remnants in the Big Darby Creek watershed include the Bigelow Cemetery (Madison County), Smith Cemetery (Madison County) and Milford Center Prairie (Union County) State Nature Preserves.
Bluff Prairie Ecosystem
Typically, bluff prairie communities are found along bluff tops, hillcrests and moderate to steep eroding slopes along major streams or tributaries that have cut through till and continue to erode and undercut their slopes. Soils are generally shallow, well drained to excessively well drained and occur over glacial outwash or till. The vegetation is generally sparse and sites are typically very small (less than one acre). Herbaceous species composition is variable but trends toward dry-adapted prairie species. Woody canopy cover is generally less than 25-75% and represented by oak species, including black oak, with associated hickories and occasional red cedar.
Their location makes them inaccessible to mechanized agriculture and has been a factor in their survival into the 21st century and their significance as a source for native prairie seeds. Bluff prairies, sometimes called slump prairies because of the relation to rapidly eroding, high slope areas, are most commonly found along and near the mid to lower reaches of the Big Darby Creek mainstem, as in Battelle-Darby Metro Park and downstream.
Some indicative plant species of tallgrass and bluff prairies are:
Andropogon gerardii – (big bluestem)
Schizachryum scopariums – (little bluestem)
Sorghastrum nutans – (Indian grass)
Tradescantia ohiensis – (Ohio spiderwort)
Allium cernuum – (nodding wild onion)
Astragalus canadensis – (Canada milk vetch)
Cassia fasciculata – (partridge pea)
Euphorbia corollata – (flowering spurge)
Gentiana quinquefolia – (stiff gentian)
Lithospermum canescens – (hoary puccoon)
Castilleja coccinea – (Indian paintbrush)
Echinacea purpurea – (purple coneflower)
Helianthus grosseserratus – (sawtooth sunflower)
Liatris squarrosa – (scaly blazing star)
Ratibida pinnata – (gray-headed coneflower)
Silphium trifoliatum – (whorled rosinweed)
Sporobolus asper – (rough dropseed)
Aesclepias tuberosa – (butterfly weed)
Sabatia angularis – (rose pink)
Dasistoma microphylla – (mullein foxglove)
Swertia caroliniensis – (American columbo)