In Sandy Substrates, Tidal Inundation Stimulates Plant Biomass Production Across Species: Implications for Wetland Restoration

Abstract Native wetland plantings are a critical part of tidal wetland restoration, serving common goals such as substrate stabilization and carbon storage, but there is insufficient guidance on selecting species based on site conditions (particularly tidal inundation and salinity). We used marsh organ elevation gradient platforms at mesohaline and oligohaline sites in a Chesapeake Bay (Maryland) subestuary to determine biomass and soil organic matter production of native clonal species Peltandra virginica , Panicum virgatum , Spartina cynosuroides , Spartina patens , Distichlis spicata , and, for comparative purposes, the invasive Phragmites australis grown in a sandy substrate. We expected that biomass would decrease with increasing flood frequency due to anaerobic stress on rhizomes and roots. Surprisingly, the aboveground and total biomass of all species increased with greater flood frequency. Belowground biomass varied less with elevation and was generally higher than aboveground biomass. We attribute these unexpected results to the sandy substrate used in the experiment (50% sand and 50% vermiculite). We hypothesize that the sandy substrate provided little carbon for microbial respiration and had high drainage, resulting in minimal anaerobic stress. Our results inform wetland restoration contexts with coarse-textured wetland substrates, such as wetlands created for erosion protection (e.g., living shorelines) or for stabilizing dredged material, demonstrating that native wetland clonal species and invasive Phragmites australis can thrive under high tidal flooding with sandy soils.