Time-Dependent Impacts of Cattail Invasion in a Great Lakes Coastal Wetland Complex

The aggressive cattail species Typha X glauca and Typha angustifolia have established in wetlands across the Great Lakes region, decreasing native plant diversity and altering environmental conditions. We relied on a parallel study in which 80 years of historical aerial photographs from a large Lake Michigan wetland complex were used to map the spread and determine the age of invasive cattail stands. Floristic, edaphic, and environmental data were collected from plots across an invasion-age gradient. Compared with reference uninvaded sites, litter mass more than doubled within 10 years of invasion (P < 0.001), plant diversity declined by more than 50% within 25 years of invasion (P = 0.003), and soil organic depth was more than 29-cm deeper in areas invaded for more than 35 years compared with areas invaded for 10 years or less (P = 0.006). These time-dependent changes in plant communities, soil, and environmental conditions fundamentally alter the structure of invaded wetlands, likely influencing a range of ecosystem services.