Soil seed stocks of tropical hardwood hammocks in southern Florida : implications for restoration

Tropical hardwood hammocks are evergreen, broad-leaved forests occurring in southern Florida and throughout the Caribbean basin. 1 examined the soil seed stocks of hardwood hammocks in six south Florida sites. Three sites represent urban, fragmented forests situated along coastal uplands of mainland Florida and three sites are located in relatively undisturbed forests in northern Key Largo. The purpose of my research was to determine the species composition and abundance of seeds in the soil, and to determine the abundance and distribution of exotic seeds in this community. Seed bank characteristics were determined by collecting soil samples every 5 m along two 50 m transects at each site. A total of 1970 seedlings, representing 64 species emerged from all combined soil samples. Approximately, 4% of the seedlings were exotic. Sites differed in total seed density and in species composition of the seed bank. Detrended Correspondence Analysis showed distinct species composition patterns from mainland and Keys seed banks. Based on seed bank patterns and phenological data, I classified seed bank strategies for hardwood hammock species. To understand the potential role of a soil seed bank in restoration of hardwood hammocks, I examined how buried seeds corresponded to the vegetation. Importance values, based on relative basal area, relative frequency, and relative cover were calculated for trees and shrubs. I compared these importance values with species percentages of seeds recovered in the soil. Similarity of buried seeds to the vegetation was low, using Jaccard\u27s coefficient. Detrended Correspondence Analysis showed distinct seed bank and vegetation associations. A comparison of successional stages represented in the vegetation and the seed bank shows that there are consistent ratios between early, mid and late successional species among the sites. Based on these results, I recommend that the seed bank be considered when restoring tropical hardwood forests