Seed Rain of Restored and Natural Prairie Wetlands

Abstract

In prairie wetland restorations, seeds may be limiting plant recolonization but this has never been quantified in the field. We evaluated the seed rain in restored and natural wetlands to determine if seed limitation constrains plant recolonization. We were particularly interested in determining whether Carex species, dominant vegetation of seasonally flooded zones, are seed limited in restorations. We quantified seed rain over two years using seed traps and compared seed rain with on-site vegetation and seed banks. The seed rain, vegetation, and seed banks of restorations were dominated by annual species rather than the target non-invasive, native perennial vegetation. Invasive perennials were not dominant in the seed rain, vegetation, or seed banks of new restorations, despite the fact that they are abundant in many older restorations. The seed rain of natural wetlands was dominated by invasive perennials, which did not reflect the prevalence of native perennial vegetation onsite. Carex species were seed limited in both wetland types. Carex species need to be sown into prairie wetland restorations to overcome dispersal limitations and to pre-empt the perennial invasive species. In addition, landscape-scale perennial invasive species management is necessary to reduce the seed supply of undesirable species to all wetlands.

Carex Seedling Emergence in Restored and Natural Prairie Wetlands

“…At the beginning of the experiment, the plots in the restored sites had <5% vegetative cover but by the end of the first growing season were dominated by annual, agricultural weeds, while the plots in the natural wetlands were heavily vegetated from the start of the experiment through the end likely because they were dominated by perennial species (Table 2). The dominant species in all plots reflected the dominant vegetation described for restored and natural wetlands in a companion paper (Kettenring and Galatowitsch 2011).…”

“…To ensure that restoration sites had no existing Carex seed banks, they were selected in areas that had been under agricultural crop production for at least 50 years, which is consistent with most restorations in the region (Wienhold and van der Valk 1989). In addition, a seed bank assay confirmed a lack of a Carex seed bank (Kettenring and Galatowitsch 2011). Wetlands were reflooded in 2001, the year before they were included in this study.…”

“…In restored prairie pothole wetlands, for example, Aronson and Galatowitsch (2008) found that sites with the fewest native species were those isolated from natural wetlands and that were infrequently ponded. Propagule limitation has been well-documented in many restorations including redeveloping wetland plant communities following hydrologic restoration (Donath et al 2003;Xiong et al 2003;Neff and Baldwin 2005;Kettenring and Galatowitsch 2011). This suggests that active revegetation should be an important component of restoration practice.…”

“…In these systems, seed limitation restricts restoration success for Carex species (sedges) (Kettenring and Galatowitsch 2011), the characteristic vegetation of the seasonally flooded wet meadow zone found around the periphery of wetlands. To overcome seed limitation, practitioners may be able to accelerate succession through seeding or planting native species, a practice that could improve revegetation of the more than 60 prairie wetland Carex species (Barkley 1986), but has not been adequately evaluated.…”

The potential of soil seed banks of a eucalypt wetland forest to aid restoration

“…Nonetheless, studies that have considered the potential role of soil seed banks in wetland restoration have reached mixed conclusions. While some studies of wetlands have reported diverse seed bank floras appropriate for aiding restoration activities (Richter and Stromberg 2005;Nishihiro et al 2006;James et al 2007;Li et al 2008;Baldwin et al 2010;Tererai et al 2015), other studies have found seed banks lacking in target species for restoration (Middleton 2003;Lu et al 2010;Kettenring and Galatowitsch 2011). Conversely, other studies have suggested that the restoration of degraded environments, including wetlands, may be hampered by soil seed banks due to the prevalence of exotic plant propagules (Williams et al 2008;Eldridge and Lunt 2010).…”