LAUSR

Foundation plant species play an important functional role in modifying microenvironment through vegetation structure and by influencing soil properties. Mangroves and salt marsh differ in vegetation structure, yet offer similar ecosystem services. This work aimed to understand how different vegetation classes and abiotic factors along a latitudinal gradient of spatial and temporal complexity affect soil CO2 efflux. Soil CO2 efflux, biomass, soil properties, and soil and air temperature were measured in July 2015 and January 2016 in situ at 10 sites along a 342-km latitudinal gradient on the Atlantic coast of Florida. Mean CO2 flux values ranged from 0.41 ± 0.19 to 2.03 ± 0.19 μmol m−2 s−1 across vegetation classes, and efflux values in mangrove plots were not significantly different between sampling dates, whereas ecotone and salt marsh efflux values were. On average, CO2 flux was 1.11 ± 0.18 μmol m−2 s−1 greater in July than in January across plots. There was no significant trend between efflux and aboveground biomass and a positive trend between belowground biomass and CO2 efflux. Edaphic parameters (organic matter content (%), soil N, organic C, and pH) were comparable across all vegetation class soils and there was a positive trend between soil temperature and flux. Soil efflux had an inverse relationship with latitude; in January, there is an increase in efflux with a decrease in latitude, while in July, efflux increases with an increase in latitude. Consequently, we assert that differences in CO2 efflux were due to soil temperature and species productivity along the latitudinal gradient studied.