Control of reed canarygrass promotes wetland herb and tree seedling establishment in an Upper Mississippi River floodplain forest

Published source details Thomsen M., Brownell K., Groshek M. & Kirsch E. (2012) Control of reed canarygrass promotes wetland herb and tree seedling establishment in an Upper Mississippi River floodplain forest. Wetlands, 32, 543-555.
Share Tweet Email

Actions

This study is summarised as evidence for the following.

	Action	Category
	Introduce fragments of trees/shrubs: freshwater wetlands Action Link
	Use cutting/mowing to control problematic herbaceous plants: freshwater swamps Action Link
	Use herbicide to control problematic plants: freshwater swamps Action Link
	Introduce tree/shrub seeds or propagules: freshwater wetlands Action Link
	Physically damage problematic plants: freshwater swamps Action Link
	Use fences or barriers to protect freshwater wetlands planted with trees/shrubs Action Link

Introduce fragments of trees/shrubs: freshwater wetlands

A study in 2007–2009 in a floodplain swamp restoration site in Wisconsin, USA (Thomsen et al. 2012) reported 12% survival of planted tree cuttings over two years. All surviving individuals were willows Salix spp. No cottonwood Populus deltoides or red osier dogwood Cornus stolonifera cuttings survived at monitored points – although some surviving cottonwood cuttings were noted elsewhere in the site (not quantified). Methods: Fresh (<2-week-old), unrooted tree cuttings were planted into 16 plots in a floodplain swamp restoration site (a clearing created by a storm). Cottonwood cuttings were planted in May 2007. Black willow Salix nigra, sandbar willow Salix exigua and dogwood cuttings were planted in April 2008. All plots had been cleared of invasive reed canarygrass Phalaris arundinacea and disked in November 2006. Herbicide was then applied regularly through to November 2008). Survival was monitored for 28 cuttings situated at survey points.

(Summarised by: Nigel Taylor)
Use cutting/mowing to control problematic herbaceous plants: freshwater swamps

A replicated, controlled study in 2006–2009 in a floodplain swamp clearing invaded by reed canarygrass Phalaris arundinacea in Wisconsin, USA (Thomsen et al. 2012) found that cutting, disking and applying herbicide to invaded plots increased tree seedling abundance after 1–3 years, and increased cover of herbs other than canarygrass after three years. In three of three years following intervention, treated plots contained more tree seedlings (4–44 seedlings/m²) than untreated plots (0–5 seedlings/m²). At the same time, treated plots had lower reed canarygrass cover (7–31%) than untreated plots (83–92%). Cover of herbs other than reed canarygrass did not significantly differ between treated and untreated plots in the first two years after intervention (treated: 15–47%; untreated: 16–22%), but was higher in treated than untreated plots in the third year (treated: 35–58%; untreated: 12%). Methods: In November 2006, twenty plots (roughly 810 m²) were established in a storm-created clearing within a floodplain swamp. Sixteen canarygrass-dominated plots were treated by cutting the vegetation (with a mechanical mulcher), disking the soil, and applying herbicide (four combinations of herbicide type and dose; repeated applications in summer and autumn until November 2008). The other four plots received none of these interventions. The study does not distinguish between the effects of cutting, disking and applying herbicide. Some tree species were planted and/or sown across the whole clearing. Vegetation (excluding planted trees) was surveyed in August 2007–2009, in four 2.25-m² quadrats/plot.

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

A replicated, controlled study in 2006–2009 in a floodplain swamp clearing invaded by reed canarygrass Phalaris arundinacea in Wisconsin, USA (Thomsen et al. 2012) found that cutting, disking and applying herbicide to invaded plots increased tree seedling abundance after 1–3 years, and increased cover of herbs other than canarygrass after three years. In three of three years following intervention, treated plots contained more tree seedlings (4–44 seedlings/m²) than untreated plots (0–5 seedlings/m²). At the same time, treated plots had lower reed canarygrass cover (7–31%) than untreated plots (83–92%). Cover of herbs other than reed canarygrass did not significantly differ between treated and untreated plots in the first two years after intervention (treated: 15–47%; untreated: 16–22%), but was higher in treated than untreated plots in the third year (treated: 35–58%; untreated: 12%). Methods: In November 2006, twenty plots (roughly 810 m²) were established in a storm-created clearing within a floodplain swamp. Sixteen canarygrass-dominated plots were treated by cutting the vegetation (with a mechanical mulcher), disking the soil, and applying herbicide (four combinations of herbicide type and dose; repeated applications in summer and autumn until November 2008). The other four plots received none of these interventions. The study does not distinguish between the effects of cutting, disking and applying herbicide. Some tree species were planted and/or sown across the whole clearing. Vegetation (excluding planted trees) was surveyed in August 2007–2009, in four 2.25-m² quadrats/plot.

(Summarised by: Nigel Taylor)
Introduce tree/shrub seeds or propagules: freshwater wetlands

A study in 2006–2009 in a floodplain swamp restoration site in Wisconsin, USA (Thomsen et al. 2012) reported that seedlings of only three of five sown tree species were present. Neither black ash Fraxinus nigra nor river birch Betula nigra seedlings were present in the site within three years of sowing seeds. Seedlings of the other three sown species were present (green ash Fraxinus pennsylvanica, American elm Ulmus americana and silver maple Acer saccharinum; abundance data reported graphically) but the study does not distinguish seedlings originating from sown vs naturally arriving seeds. Methods: Between November 2006 and May 2009, seeds of five tree species (numbers not clearly reported) were broadcast across 16 plots in a floodplain swamp restoration site (a clearing created by a storm). All plots had been cleared of invasive reed canarygrass Phalaris arundinacea and disked in November 2006 (before first sowing). Herbicide was then applied regularly through to November 2008). Tree seedlings were counted in August 2007–2009.

(Summarised by: Nigel Taylor)
Physically damage problematic plants: freshwater swamps

A replicated, controlled study in 2006–2009 in a floodplain swamp clearing invaded by reed canarygrass Phalaris arundinacea in Wisconsin, USA (Thomsen et al. 2012) found that cutting, disking and applying herbicide to invaded plots increased tree seedling abundance after 1–3 years, and increased cover of herbs other than canarygrass after three years. In three of three years following intervention, treated plots contained more tree seedlings (4–44 seedlings/m²) than untreated plots (0–5 seedlings/m²). At the same time, treated plots had lower reed canarygrass cover (7–31%) than untreated plots (83–92%). Cover of herbs other than reed canarygrass did not significantly differ between treated and untreated plots in the first two years after intervention (treated: 15–47%; untreated: 16–22%), but was higher in treated than untreated plots in the third year (treated: 35–58%; untreated: 12%). Methods: In November 2006, twenty plots (roughly 810 m²) were established in a storm-created clearing within a floodplain swamp. Sixteen canarygrass-dominated plots were treated by cutting the vegetation (with a mechanical mulcher), disking the soil, and applying herbicide (four combinations of herbicide type and dose; repeated applications in summer and autumn until November 2008). The other four plots received none of these interventions. The study does not distinguish between the effects of cutting, disking and applying herbicide. Some tree species were planted and/or sown across the whole clearing. Vegetation (excluding planted trees) was surveyed in August 2007–2009, in four 2.25-m² quadrats/plot.

(Summarised by: Nigel Taylor)
Use fences or barriers to protect freshwater wetlands planted with trees/shrubs

A replicated, paired, controlled study in 2006–2009 in a floodplain swamp clearing in Wisconsin, USA (Thomsen et al. 2012) found that fencing to exclude deer before sowing tree seeds had no significant effect on tree seedling abundance but increased seedling height. After roughly three years, fenced plots contained a statistically similar number of tree seedlings (40 seedlings/m²) to open plots (28 seedlings/m²). However, seedlings in fenced plots were significantly taller (73 cm) than those in open plots (46 cm). Methods: In November 2006, sixteen pairs of 2.25-m² plots were established in a floodplain swamp restoration site (clearing created by a storm; invasive vegetation recently removed and ground disked). In each pair, one plot was fenced to exclude white-tailed deer Odocoileus virginianus (plastic mesh fence, 2 m tall) whilst the other was left open. Seeds of five tree species were sown in and around all plots between 2006 and 2009. The plots were also treated regularly with herbicide, to control an invasive grass, between 2006 and 2008). Seedlings were counted and measured in August 2009.

(Summarised by: Nigel Taylor)