Seed persistence of three species, Carex stricta, Carex hystericina and Phalaris arundinacea, in a restored wetland

Seed persistence and longevity is poorly documented for wetland plants, despite the value of this knowledge for restoration. Seed persistence is particularly important information for sedge meadows (i.e., seasonally ponded freshwater wetlands dominated by Carex spp.), which often fail to recolonize without planting and are rapidly invaded by reed canary grass (Phalaris arundinacea L.). We conducted a 17-year seed burial study along a hydrological gradient in a Minnesota wetland to assess seed persistence of P. arundinacea and two common species of sedge meadows, bottlebrush sedge (Carex hystericina Muhl. ex Willd.) and upright sedge (Carex stricta Lam.). Seed samples were placed in capsules designed to prevent seed loss while allowing for environmental influences. Six boxes, each containing 126 seed capsules (3 species x 14 exhumation years x 3 replicates), were buried in wetland soils under three hydrological conditions (regularly, seasonally, or never inundated) along two transects. Seeds were exhumed 1-, 5-, 6-, 9-, and 17-years post-burial and tested for germinability and viability. For C. stricta and P. arundinacea, seed persistence (50% survival, P₅₀) was < 1 year under all hydrologic conditions, while for C. hystericina P₅₀ was 6 yrs where never inundated and > 17 years when seasonally or regularly inundated. Seed longevity was < 17 yrs for C. stricta and P. arundinacea in locations never inundated; for other hydrological conditions and for C. hystericina, seed longevity exceeded the duration of the burial experiment. If seed persistence is typically reduced where inundation is brief, sedge meadow wetlands drained and cultivated for many decades are unlikely to have long-buried seed banks to serve as propagule sources for revegetation.