The Soil Seed Pool of Huffman Prairie, a Degraded Ohio Prairie, and its Potential in Restoration

The germinable seeds in the soil of a relict Ohio prairie were investigated to determine the composition and density of dicots of potential value in restoration. Soil samples were collected from three areas of the prairie with distinctive species compositions: swale, north upland, and south upland. Seed density and species composition were based on seedling emergence over 90 days. North upland and south upland samples yielded similar total seedling densities (5,902 and 5,109 m·) while that of the swale was greater ( 15,262 m·). Thirteen introduced and 18 native dicot species were present; seven of the latter were common in pre-settlement prairies. Sixty percent of the dicot seedlings were of native species. Swale samples contained fewer prairie species and were less diverse than those from the upland areas. Six species common in pre-settlement prairies had greater frequencies of germinable seeds than the vegetation; however, no seeds of prairie species were found that were not in the vegetation. This indicates that the seed pool may be useful in increasing densities of species already present but not in reestablishing species absent in the above-ground vegetation. INTRODUCTION Before European settlement, tallgrass prairie occupied a small but significant portion of the Ohio landscape (Nolin and Mutter 19HH). Although some prairies were plowed after settlers realized the high fertility of the soil, unplowed prairies were often used for pasture, leading to the disappearance of many prairie species and to the introduction of invasive species (Gordon 1969). Some species of prairie plants have become common in successional habitats (i.e., Oenothcra hicnnis) while others remain only in former prairie sites [i.e., Liatris .~picata (Gordon 1969)). Little remains of the original tallgrass prairie in the U.S. (Klopatek et a!. 1979), and very few prairies remain in Ohio (Gordon 1969). Restoration of prairies, begun by Greene and Curtis at the University of Wisconsin Arboretum in 1936 (Anderson 1973), has been adopted by many conservation organizations and private landowners (Burton et a!. 19HH). While some of these restoration projects are initiated on unvegetated areas, others begin with degraded prairie (Green et al. 1981, Conover and Geiger 19H9). The species composition and abundance of seeds within the soil "seed pool" and on the soil surface may be quite different from that of the vegetation (Thompson and Grime 1979, Johnson and Anderson 19H6). These seeds can yield information about the past and potential vegetation of an area. The presence of germinable seeds of a species not in the vegetation indicates that conditions have not been suitable for germination; a change in conditions could result in re-establishment of that species. Most prairie species will not have germinable seeds present in the soil (Rabinowitz 19H1, Johnson and Anderson 19H6). However, those germinable seeds which are present are generally located near the surface and in Manuscript received 2'5 May 1994 and in revised form B August 199A (#94-12). 'Present Address: Ndson Biological Laboratories. Rutgers University. Piscataway, NJ OtlWiS-10'59 OHIOJ. SCI. 94 (4): 82-86, 1994 small numbers (Rabinowitz 1981, Johnson and Anderson 1986). The seeds of most prairie species do not remain viable in the soil for long periods of time, however the seeds of forb species tend to be longer lived than those of grass species (Rabinowitz 1981, Thompson 1992). As Hutfman Prairie has never been greatly altered by agriculture or other development (Nolin and Mutter 1988), the seeds of many forb species may remain dormant within the soil. If the seeds of prairie forbs are present, restoration of their populations by manipulation of germination conditions may be worthwhile. The present study focuses on the species composition and abundance of clicot germinable seeds in the soil of a relict Ohio prairie. The objective of this study was to characterize the species composition of germinable seeds in three different areas of a degraded prairie and to assess the potential of manipulating germination conditions in prairie restoration. MATERIALS AND METHODS Study Site The Huffman prairie (~32 ha) is one of the largest remaining tallgrass prairies in Ohio. It is contained within the Wright-Patterson Air Force Base, approximately 8 k northeast of Dayton (36° 45' N, 84° 15 W). The degenerate condition of the prairie is the result of a long history of human use. It was grazed for many years and a portion has been drained. Following drainage, the prairie was regularly mowed by the Air Force until 19H4 (Nolin and Mutter 19HH). Since then, portions of the prairie have been burned as part of the management program, and it bas been designated a state natural landmark. The Ohio Chapter of The Nature Conservancy is now the steward of the prairie. Three ditferent areas of the prairie were recognized: "north upland," "south upland,'' and "swale'' (Fig. 1). The north upland area was dominated by native prairie grasses (Andropogon gerardii and Sorghastrum nutans) with little forb cover. The south upland area was also dominated by grasses, but had more forbs than the north 01110 .JOURNAL OF SCIENCE S . .f. MFINFI{S AND D. L. (;ORCIIOV