Feral hog disturbance alters carbon dynamics in Southeastern US salt marshes

Disturbances that remove primary producers and alter substrate chemistry commonly influence ecosystem carbon dynamics. Because coastal wetlands are especially effective in sequestering carbon, quantifying how disturbances may alter their ability to perform this climate-regulating function is important for assessing their carbon storage potential. Here, we quantified soil respiration, litter decomposition, and soil organic carbon (SOC), as a proxy for carbon storage, in areas disturbed by invasive feral hogs Sus scrofa and in adjacent, undisturbed areas within 3 southeastern US salt marshes. Contrary to our hypothesis that hog overturning of soils would stimulate soil respiration, this metric was lower and both surface and subsurface litter decomposition rates were similar in disturbed relative to undisturbed areas across all sites. SOC was lower in disturbed versus undisturbed areas at 2 sites as hypothesized, but higher at 1 site. Surveys and analyses reveal that lower and less variable infauna, plant, and benthic algae densities likely suppressed soil respiration in hog-disturbed versus undisturbed areas, while the offsetting effects of lower invertebrate densities and higher soil temperature likely caused decomposition to be consistent within and outside of disturbed areas. Conversely, between-site variation in disturbance intensity, plant canopy structure, and burrowing crab densities mediated the SOC response. These findings suggest that hog removal of plants and disruption of soils can cause tracts of marsh to transition from carbon sinks to sources where these disturbances are intense enough to prohibit rapid plant recovery and promote the gradual respiration of carbon stocks from denuded soils.