Vegetation and seedbank composition of temporarily flooded Carex meadows and implications for restoration

Seedbanks are likely an important source of propagules for the revegetation of many kinds of restored wetlands. Seedbank composition and extant vegetation was described for 12 temporarily-flooded meadows dominated by Carex spp. in east central Minnesota (USA) to determine if they contain abundant seed reserves typical of emergent and littoral marshes. Seedbank densities and species composition were estimated from both seedling emergence assays and seed separation to minimize the likelihood of underestimation. In addition, seedling emergence assays were conducted on soil that was cold stratified for 4 mo and on soil taken directly from the field. An average of 28 species were found in the vegetation and 26 species in the seedbank of each wet meadow. Of the three seedbank assays, the fewest species were detected from stratified seedling emergence samples (x=7) and the most from separated seed (x=18). On the average, 12 species were found in unstratified seedling emergence samples. Similarly, the highest seed densities were estimated by seed separation (x=2140 m^-2), followed by unstratified emergence (x=916 m^-2), and stratified emergence (x=328 m^-2). Carex stricta/haydenii, a dominant wet meadow species, was not detected by emergence assays. Emergence assays were reliable for most other species. Regardless of the seedbank method used, the seed densities of the wet meadows in this study are comparable to those reported previously for Carex-dominated wetlands; that is, lower than those of emergent and littoral wetlands. Minimal seed reserves and disproportionately high abundance's of invasives (Typha spp., Phalaris arundinacea) may limit the ability of natural wetlands to act as effective propagule sources for revegetation during restoration.