All data were collected in 2020 or 2021 from 27 tidal wetland sites located along the East, Gulf, and West coasts of the conterminous United States and Alaska. Twenty of the 27 sites were located within the National Estuarine Research Reserve System (NERRS). Porewater samples were collected at 367 locations (plots, 50x50cm) to measure the concentrations of porewater methane, sulfate, ammonium, total iron, and chloride. Within each plot, a survey of aboveground species richness was conducted and scored using the Braun-Blanquet scale. Each live species present in the plot was given a score based on the number of stems and/or the percent of coverage in the plot. Cover was also recorded for dead aboveground plant matter, bare ground, and open water. Optionally, a small section (10x10 cm or 25x25 cm) of the plot was clipped within 2 cm of the sediment surface to calculate a dried biomass weight. The latitude, longitude, and elevation of each plot was also optionally recorded, resulting in varying levels of precision. These data were collected in partnership with the NERRS system in support of the manuscript (in prep), “Controls on spatial variation in porewater methane concentrations across U.S. tidal wetlands”.

All data were collected in 2020 or 2021 from 27 tidal wetland sites located along the East, Gulf, and West coasts of the conterminous United States and Alaska. Twenty of the 27 sites were located within the National Estuarine Research Reserve System (NERRS). Porewater samples were collected at 367 locations (plots, 50x50cm) to measure the concentrations of porewater methane, sulfate, ammonium, total iron, and chloride. Within each plot, a survey of aboveground species richness was conducted and scored using the Braun-Blanquet scale. Each live species present in the plot was given a score based on the number of stems and/or the percent of coverage in the plot. Cover was also recorded for dead aboveground plant matter, bare ground, and open water. Optionally, a small section (10x10 cm or 25x25 cm) of the plot was clipped within 2 cm of the sediment surface to calculate a dried biomass weight. The latitude, longitude, and elevation of each plot was also optionally recorded, resulting in varying levels of precision. These data were collected in partnership with the NERRS system in support of the manuscript (in prep), “Controls on spatial variation in porewater methane concentrations across U.S. tidal wetlands”.