Testing the efficacy of seed and plant transfer by topsoil augmentation on reclaimed phosphate-mined uplands

摘要

Topsoil was collected from a burned flatwoods and an unburned flatwoods and applied as a thick layer and a thin layer to a reclaimed overburden site and a reclaimed sand tailings site. One donor site was burned in the growing season to stimulate seed production of fire-dependent species such as wiregrass (Aristida beyrichiand). After seed had dispersed, topsoil was removed from both burned and unburned donor topsoil sites and transferred to a reclaimed overburden site and a nearby reclaimed sand tailings site and applied as 16 cm and 8 cm thick layers in a random split plot design that included untreated control plots at each site. Soil parameters were analyzed from topsoil, overburden, and sand tailings collected two months after addition of topsoil. The addition of topsoil to the overburden site decreased bulk density and C:N ratio, and increased total C, total N, Ca, Mg, K, Zn, Mn, and Na of the surface soil. The pH, C:N ratio, Ca, P, and Zn concentrations decreased while the total C and N increased in the surface soil at the sand tailings site. Vegetation was monitored at the end of the first and second growing seasons. Transfer of topsoil resulted in a high species richness of desirable species at both the overburden and sand tailings sitesat the end of the first growing season. A higher density and coverage of desirable species persisted through the end of the second growing season at the overburden site but not the sand tailings site. The sand tailings site contained a high weed cover of natalgrass (Rhynchelytrum repens) andtorpedograss (Panicum repens} in adjacent areas which presumably contributed to a heavy weed cover within the experimental plots during the second year. The effect of an extreme drought experienced in 1998 was alsomore pronounced on the droughty sand tailings soils. A more favorable moisture regime at the overburden site may have contributed to both greater reproduction rates and more successful establishment of mesic flatwoods species. Wiregrass was more frequently associated with topsoil from burned flatwoods whereas saw palmetto (Serenoa repens) was more frequently associated with topsoil from unburned flatwoods. Dichanthelium aciculare was also more prevalent in the burned plots while D. portoricense was morecommon at the unburned plots. Thickness of topsoil affected establishment of some species, however, this effect was not as pronounced as were burning, soil type, and year.