Emergent wetlands in eastern North America are being replaced by a non-native lineage of Phragmites australis. On the Ontario side of Lake Erie, the marsh communities most often replaced by P. australis are rare meadow marsh, a habitat type classified as Critically Imperiled/Imperiled (S1/S2) under the Ontario Provincial Ranking System, and cattail marsh, which is dominated by the non-native hybrid Typha x. glauca. My research focuses on how primary production and decomposition rates differ among invaded P. australis, emergent cattail, and meadow marshes. Changes to net primary production and decomposition rates could have implications for carbon cycling. Using a litter transplant experiment to measure decomposition rates, I assessed the relative importance of the change in litter source and the change in edaphic conditions caused by P. australis. To look at the effect of invasion on primary production, I examined above- and belowground standing crop biomass in invaded P. australis, meadow and cattail marshes.
Preliminary results from 2016 indicate that aboveground biomass is greater in invaded P. australis marsh (1714 g/m2 +/- 418 g) than meadow (779 g/m2 +/- 454 g) or cattail (1359 g/m2 +/- 340 g) marshes. Belowground biomass, however, was greatest in cattail marsh (262 g/m2 +/- 198 g), though still higher in P. australis invaded marsh (138 g/m2 +/- 69 g) than in meadow marsh (67 g/m2 +/- 56 g). In terms of decomposition, I observed that C. canadensis litter decomposes more rapidly than P. australis or Typha spp. litter. Conversely, the rate of decomposition was higher in invaded and cattail marshes than in meadow marsh. My results underscore that the effect of invasive P. australis on primary production and decomposition rates in marshes is dependent on which vegetation community is being replaced.