Seed Bank—Vegetation Dynamics along a Restoration Management Gradient in Pine Flatwoods Ecosystems of the Florida Gulf Coast

Abstract

Pine flatwoods ecosystems of the Gulf Coastal Plains of the southeastern United States are known for their species richness, mainly contributed by herbaceous groundcover. However, intensive silvicultural operations and exclusion of fire over a large extent of these ecosystems in the past century has led to a serious depletion of groundcover diversity. Consequently, restoration of these ecosystems has become a high priority for ecological management of forests in the area. The present study was carried out at mesic-hydric flatwoods sites in northwest Florida to examine the effects of restoration activities, including varying intensities of thinning and prescribed burning, on the dynamics of the vegetation and the soil seed bank composition and structure. Three site conditions—degraded, partially restored, and restored—representing a restoration management gradient were sampled for aboveground vegetation and soil seed bank. Vegetation and seed bank composition changed following restoration activities. However, there was little effect on the seed bank structure across the site conditions. A total of 24, 59, and 124 species in the aboveground vegetation, and 26, 39, and 64 species in the seed bank were observed in degraded, partially restored, and restored site conditions, respectively. Most of the species in the seed bank were ruderal, although native. The effect of site conditions on seed density and seed species richness and diversity was not statistically significant. However, these characteristics did vary significantly with the soil depth (main effect) where the soil sample was taken. Higher seed densities were observed in top 0–5 and 5–10 cm than 10–15 cm soil depths across all sites. Seed banks tended to resemble each other more than the vegetation and the vegetation and seed bank across all sites. The presence of mostly ruderal species in seed bank in degraded site indicates that seed bank is not a good source of regeneration of typical flatwoods communities.