Christine Rohal (2016)

“Thanks to the generous support from the Wetland Foundation, I was able to frequently visit my experimental Phragmites control plots in wetlands across the Great Salt Lake, Utah. I initiated this experiment in the summer of 2012 in order to assess multiple treatments for their ability to control the wetland invasive plant, Phragmites australis, and promote the reassembly of native species. The treatments are 1) summer glyphosate spray, followed by a winter mow; 2) summer imazapyr spray, followed by a winter mow; 3) fall glyphosate spray, followed by a winter mow; 4) summer mow, followed by a fall glyphosate spray; 5) summer mow then cover plots with heavy-duty black plastic (i.e., a solarization treatment); and 6) untreated control. Treatments were conducted for three consecutive years.

In the summer of 2016, I returned to the experiment for the fifth year to assess the long-term plant community response to our Phragmites control efforts. I found that summer herbicide treatments resulted in higher cover of Phragmites than fall herbicide treatments. Nevertheless, all treatments resulted in an average of 40-50% cover of Phragmites by year five, indicating the traditional three year management sequence we enacted may not be enough to see effective long-term results. Native species return was variable across sites, with some plots seeing high levels of recovery, and others with very little. This variability was driven primarily by hydrology: wetter sites saw a greater reduction in Phragmites cover, and a more vigorous native plant return. The establishment of important habitat-forming perennial bulrushes was minimal across all sites, indicating revegetation efforts might be needed to meet specific restoration targets.

The financial help from the Wetland Foundation was invaluable in allowing me to travel to sites to collect data for this experiment in its fifth year. Research funding is challenging to maintain for long-term experiments, but long-term monitoring is essential in understanding the effectiveness of management actions.”