Suppression of reed canarygrass for large-scale floodplain forest restoration across four sites in southeast Minnesota, USA
Kiser, William R.
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Experiments can provide insight on whether invasive plant dominance is caused by superior competitive ability (driver) or by environmental changes that facilitate plant invasion (passenger). Reed canarygrass (Phalaris arundinacea, hereafter RCG) displaces native plants and forms near-monocultures in North American wetlands. In the Upper Mississippi River (UMR) system, floodplain forests are negatively impacted by RCG invasion. We tested two RCG control techniques on a reforestation project at four sites in SE Minnesota. Treatments consisted of (1) applying glyphosate (Rodeo) herbicide and (2) mulching followed by applying sulfometuron methyl (Oust XP) herbicide. Treatments were applied in Fall 2016. We monitored herbaceous plant response and RCG performance over the 2017 and 2018 growing seasons. We also calculated the number of days flooded in each plot for the 2017 growing season using linear interpolation of river gauge data. Both treatment methods significantly reduced RCG performance relative to controls during the 2017 growing season; however, RCG performance in treatment plots was similar to control plots during the 2018 growing season. Herbaceous plants increased in species richness and cover relative to control plots, although volunteer plant diversity varied among sites. These results indicate that follow-up herbicide applications are necessary to control RCG to facilitate tree establishment. Further, flooding and lack of native propagules may be factors in RCG invasions. Our results indicate that RCG may behave as a driver in some parts of the UMR and as a passenger in parts of the UMR that are more affected by hydrologic alteration.
Restoration ecology -- Minnesota
Forest restoration -- Minnesota