Interspecific differences in dead plant buffering capacity alter the impact of acid rain on decomposition rates in tidal marshes

Simulated acid rain did not alter respiration rates of microbial associations on dead Spartina alterniora from Delaware salt marshes or on dead Carex lyngbyei from Oregon brackish marshes. Since these dead plant-microbe associations have a strong buffering capacity for acid rain, the microbial associations did not experience a low pH. In contrast, Phragmites australis has a low buffering capacity and microbial respiration was reduced at least 25 % by acid rain. When dead plant-microbe associations from freshwater marshes and various terrestrial plant populations were immersed in simulated acid rain, the rain water equilibrated at pH's from 3.9 to 5.0 and were characteristic of the various species. The different buffering capacities of such dead plant-microbe associations may explain the inconsistent results published from decomposition studies and may serve as a quick and easy method of assessing the probable impact of acidic deposition on decomposition processes.