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

Published source details Lawrence B.A., Lishawa S.C., Rodriguez Y. & Tuchman N.C. (2016) Herbicide management of invasive cattail (Typha × glauca) increases porewater nutrient concentrations. Wetlands Ecology and Management, 24, 457-467.
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This study is summarised as evidence for the following.

	Action	Category
	Use cutting/mowing to control problematic herbaceous plants: freshwater marshes Action Link
	Use herbicide to control problematic plants: freshwater marshes Action Link

Use cutting/mowing to control problematic herbaceous plants: freshwater marshes

A replicated, controlled, before-and-after study in 2013–2014 in twelve artificial marshes invaded by hybrid cattail Typha x glauca in Michigan, USA (Lawrence et al. 2016) found that a single mow had no significant effect on native plant richness, density or biomass one year later. After one year, mown and unmown marshes had statistically similar native plant richness (mown: 1.8–4.5; not mown: 4–4.5 species/2 m²), density (mown: 190–560; not mown: 300 stems/m²) and above-ground biomass (mown: 160–180; not mown: 440 g/m²). The same was true for cattail density (mown: 17; not mown: 44 stems/m²) although above-ground cattail biomass was lower in mown plots (mown: 90; not mown: 750 g/m²). Most outcomes also did not significantly differ between treatments after one month, the exceptions being native plant biomass (mown: <10; not mown: 260 g/m²) and cattail density (mown: 5–6; not mown: 55 stems/m²). Before mowing, vegetation was statistically similar in marshes destined for each treatment (native richness: 2.7–4.3 species/2 m²; native density: 150–230 stems/m²; native biomass: 320–380 g/m²; cattail density: 63–69 stems/m²; cattail biomass: 1,080–1,130 g/m²). Methods: In July 2013, all vegetation was mown in eight experimental marshes (1 x 2 m area, 1 m soil depth). The marshes had been created in 2002 and planted (i.e. deliberately invaded) with hybrid cattail in 2004. Cuttings were left in four marshes but removed from the other four. Four additional marshes were not mown. Plant species, density and height were recorded in all marshes immediately before, one month after and one year after mowing. Above-ground dry biomass was calculated from height measurements.

(Summarised by: Nigel Taylor)
Use herbicide to control problematic plants: freshwater marshes

A replicated, controlled, before-and-after study in 2013–2014 in eight artificial marshes invaded by hybrid cattail Typha x glauca in Michigan, USA (Lawrence et al. 2016) found that applying herbicide to the vegetation reduced native plant richness, density and biomass. After one year, there were no living plants in marshes treated with herbicide: richness, density and biomass, of both native plants and hybrid cattail, were zero. All metrics were significantly lower than in untreated marshes (where native richness: 4.5 species/2 m²; native density: 300 stems/m²; native biomass: 440 g/m²; cattail density: 44 stems/m²; cattail biomass: 745 g/m²). Results were generally similar after one month, although native plant richness had not yet declined in treated marshes (see original paper). Before treatment, vegetation was statistically similar in all marshes (native plant richness: 3.5–4.3 species/2 m²; native plant density: 190–230 stems/m²; native plant biomass: 350–430 g/m²; cattail density: 66–69 stems/m²; cattail biomass: 1,080–1,130 g/m²). Methods: In July 2013, glyphosate-based herbicide was spread onto all plant stems in four experimental marshes (1 x 2 m area, 1 m soil depth). The marshes had been created in 2002 and planted with cattail (i.e. deliberately invaded) in 2004. Four additional marshes were left untreated. Plant species, density and height were recorded in all marshes immediately before, one month after and one year after treatment. Dry above-ground biomass was calculated from height measurements.

(Summarised by: Nigel Taylor)