Long‐term suppression of wetland methane flux following a pulse of simulated acid rain

Wetlands are a potent source of the radiatively important gas methane (CH 4 ). Recent findings have demonstrated that sulfate (SO 4 2− ) deposition via acid rain suppresses CH 4 emissions by stimulating competitive exclusion of methanogens by sulfate‐reducing microbial populations. Here we report data from a field experiment showing that a finite pulse of simulated acid rain SO 4 2− deposition, as would be expected from a large Icelandic volcanic eruption, continues to suppress CH 4 emissions from wetlands long after the pollution event has ceased. Our analysis of the stoichiometries suggests that 5 years is a minimum CH 4 emission recovery period, with 10 years being a reasonable upper limit. Our findings highlight the long‐term impact of acid rain on biospheric output of CH 4 which, for discrete polluting events such as volcanic eruptions, outlives the relatively short‐term SO 4 2− aerosol radiative cooling effect.