Intra-Floodplain Seed Dispersal Limitation and Wetland Community Restoration

Abstract

The broadleaf marsh community in the post-restoration reaches of the Kissimmee River floodplain, Florida, US, has failed to achieve the expected dominance based on pre-disturbance conditions. We examined the hypothesis that seed dispersal is a limiting factor delaying the expansion of characteristic taxa of a dominant wetland plant community, broadleaf marsh, from remnant populations into a partially restored river floodplain. Hydrochory and anemochory seed traps were deployed in the Kissimmee River for two week periods during four sampling periods over the course of a year. Study plots were divided among an area influenced by backwater effects from a downstream water control structure and the substantially drier floodplain with more fragmented and degraded broadleaf marsh communities to the north. Seed trapping showed that seeds of characteristic broadleaf marsh taxa, e.g., bulltongue arrowhead (Sagittaria lancifolia), pickerelweed (Pontederia cordata), and common buttonbush (Cephalanthus occidentalis), were only rarely dispersed and in small volumes north of the confluence of Oak Creek. Seed limitation due to a partially restored physical environment may be one of the factors contributing to minimal recovery of wetland communities in the Kissimmee River floodplain. As with fragmented regional scale landscapes with substantial distances among patches and an inhospitable matrix ecosystem, our research indicates that seed limitation may also be an issue for wetland restoration at local scales in contiguous floodplain wetlands such as the Kissimmee River. Active revegetation practices may be necessary for accelerating expansion of plant communities in large-scale river/floodplain restoration projects where local seed sources are spatially and hydrologically constrained.