Wetland invasion by Typha × glauca increases soil methane emissions

Wetland invasion by monotypic dominant plants can alter the physicochemical and biological properties of soils that affect methane emissions, a potent greenhouse gas. We examined the effects of Typha × glauca invasion on soil methane using laboratory incubation and controlled mesocosm experiments. Typha-invaded soils collected from three Midwestern (USA) wetlands had greater methane production potential during laboratory incubation than soils dominated by native wet meadow vegetation. Ten years post-invasion of native plant-dominated mesocosms, Typha increased methane emissions at least three-fold (native: 15.0 ± 10.5 mg CH4-C m−2 h−1, median: 6.1 mg CH4-C m−2 h−1; Typha: mean: 45.9 ± 16.7 mg CH4-C m−2 h−1, median: 26.8 mg CH4-C m−2 h−1) under high (+10 cm) water levels, though methane emissions were negligible under low (-10 cm) water levels. Methane emissions were positively correlated with soil carbon, nitrogen, and aboveground biomass, all of which were greater in Typha-invaded mesocosms. Together, our data suggest that replacement of large tracts of native wetlands throughout eastern North America with monocultures of invasive Typha could alter regional methane emissions.