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

Abstract

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.

Negative competitive effects of invasive plants change with time since invasion

“…In addition, subtle ecosystem-level impacts such as changes to soil characteristics may accrue over time, such that the extent of the impact may not be observed for decades; such long-term cumulative impacts are generally caused by ecosystem engineers (see Crooks 2002, Strayer et al 2006). Higher abundance levels may also contribute to higher impacts measured at more established sites; however, only two of the six correlative studies reported higher abundances with time since invasion (Mitchell et al 2011, Brandner et al 2013. Furthermore, high abundances of an invader can, in some cases, lead to reduced ecological impacts owing to interference competition (Kornis et al 2014).…”

Herbicide management of invasive cattail (Typha × glauca) increases porewater nutrient concentrations

“…It rapidly expands in response to nutrient enrichment (Woo and Zedler 2002) and hydrologic changes (Boers and Zedler 2008;Hall and Zedler 2010;Lishawa et al 2010), reducing waterfowl habitat (Leitch et al 1997) and plant diversity (Frieswyk and Zedler 2006;Tuchman et al 2009), as well as altering ecosystem functions such as methane emissions (Lawrence et al unpublished data) and denitrification potential (Lishawa et al 2014). Dense litter accumulates in Typha-invaded wetlands (Mitchell et al 2011;Vaccaro et al 2009), promoting positive feedbacks that sustain the invaded state (Zedler 2009). Typha litter reduces sunlight penetration, moderates soil temperatures, and reduces native seed germination (Farrer and Goldberg 2009;Larkin et al 2012a;Vaccaro et al 2009).…”

Hybrid Typha×glauca outperforms native T. latifolia under contrasting water depths in a common garden

“…Similarly, Mitchell et al (2011) have shown rapid declines in the diversity of native plants in a region where hybrids are likely to be the most common type of cattail. By contrast, in the eastern Great Lakes and St. Lawrence Seaway regions, which includes the area from which the material for this study was collected, T. latifolia outnumbers T. angustifolia S.…”

“…The dominance of Typha hybrids in wetlands is deleterious to biodiversity: hybrids are taller (Galatowitsch et al 1999) and more productive than T. latifolia, contributing large amounts of slowly decaying litter that cover the soil surface, altering temperature and soil nutrients, excluding light, and ultimately leading to the reduction of native plant diversity (Angeloni, Jankowski, Tuchman, & Kelly, 2006;Boers, Veltman, & Zedler, 2007;Farrer & Goldberg 2009;Tuchman et al, 2009;Travis et al, 2010;Mitchell et al, 2011;Larkin, Freyman, Lishawa, Geddes, & Tuchman, 2012). Ecological dominance of hybrids might arise via the segregation of novel recombinant genotypes that are better adapted than parental genotypes (Hochholdinger & Hoecker, 2007;Donovan, Rosenthal, Sanchez-Velenosi, Rieseberg, & Ludwig, 2010), and/or the masking of deleterious recessive alleles (Prentis, Wilson, Dormontt, Richardson, & Lowe, 2008).…”