September 2014 ECOLOGICAL RESTORATION 32:3 • 249 Ecological Restoration Vol. 32, No. 3, 2014 ISSN 1522-4740 E-ISSN 1543-4079 ©2014 by the Board of Regents of the University of Wisconsin System. RESEARCH ARTICLE Intra-Floodplain Seed Dispersal Limitation and Wetland Community Restoration Scott H. Markwith, Garren Mezza, Stevee N. Kennard and Stephen G. Bousquin ABSTRACT The broadleaf marsh community in the post-restoration reaches of the Kissimmee River loodplain, 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 loodplain. 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 inluenced by backwater effects from a downstream water control structure and the substantially drier loodplain 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 conluence 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 loodplain. 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 loodplain wetlands such as the Kissimmee River. Active revegetation practices may be necessary for accelerating expansion of plant communities in large-scale river/loodplain restoration projects where local seed sources are spatially and hydrologically constrained. Keywords: anemochory, broadleaf marsh, hydrochory, Kissimmee River, macrophytes, passive restoration B y understanding the processes driving succession, scientists can suggest ways to increase rates at which desired states, i.e. reference conditions, are reached through the process of restoration (Temperton et al. 2004). In many communities, the availability of propagules is a limiting factor in reaching those desired states (Robin- son and Handel 1993, Guariguata et al. 1995, Lamb et al. 1997, as cited in Young et al. 2001). Increasingly, the assumption that propagules will be readily available for colonization of physically restored areas is being questioned (Galatowitsch and van der Valk 1996, Zobel et al. 2006, Trow- bridge 2007). Restoration of physi- cal processes may be a prerequisite to successful ecological restoration, but may not be suicient (Suding et al. 2004, Trowbridge 2007). Research in loodplain wetlands in Europe and the U.S. indicates that dispersal limitation may be a problem in these ecosystems (Bakker and Berendse 1999, Donath et al. 2003, Trowbridge 2007). Nar- rowing or elimination of the dispersal niche (i.e. the set of environmental conditions that determine where a seed arrives) with hydrologic altera- tion in loodplains may be respon- sible for some limitation, but Young et al. (2005) suggest the niche may be extended with restoration. Seeds of wetland plants can be efectively dispersed by water (hydro- chory), wind (anemochory), or ani- mals (zoochory). hese dispersal processes are inluential in ecologi- cal restoration, can be afected by low regulation and climate change (Nilsson et al. 2010), and can give advanced warning of invasive or exotic species colonization (Nef and Baldwin 2005). Wetland plant species can be dispersed by several diferent mechanisms, but hydrochory is typi- cally the primary vector in wetland systems (Nef and Baldwin 2005) and has a long scientiic pedigree recog- nizing its population and commu- nity level importance (Ridley 1930, Skoglund 1989, Boedeltje et al. 2003, Merritt et al. 2010, Markwith and Leigh 2008, Monette and Markwith 2012). Anemochory is often over- looked due to hydrochory’s preemi- nence in wetlands, but anemochory plays a key role in dispersing small, lightweight, speciically adapted seeds (Nef and Baldwin 2005, Soons 2006). Both anemochory and zooch- ory can transport seeds over long dis- tances (Ozinga et al. 2004), although in lower densities than hydrochory, and unlike water can disperse seeds in all directions, including areas of the wetland that are not connected by surface water lows (Soons 2006).