Concurrent Session: Wetland challenges
10:45 AM - 12:00 PM Wed
Title: After Phragmites: Testing the efficacy of multi-year herbicide treatment in Wisconsin's Lake Michigan Basin
Abstract: Non-native Phragmites australis is ubiquitous throughout eastern Wisconsin and, because of its negative effects on wetland function, has long been the focus of statewide management efforts. To control the spread of non-native Phragmites, the Wisconsin DNR conducted GLRI-funded herbicide treatment at thousands of sites across Wisconsin's Lake Michigan Basin from 2014 - 2020. In 2021, sites were monitored to test the efficacy of treatment and to observe plant community response, although no pre-treatment plant data had been collected. We hypothesized that differences in site accessibility (road, hydro, or wetland) and treatment sequence (which included total spray count, 0-6 years) would result in different species richness and floristic quality among sites. We developed a GIS model to randomly select 90 sites. We recorded observed species along transects and calculated Floristic Quality Indices (FQIs) for quality comparisons among sites. Wetland sites had a significantly greater species richness than road sites. Both wetland and hydro sites had significantly greater FQIs than road sites. Species richness and FQI were significantly higher in sites sprayed ≥4 times. Treatment sequence was not significant. Phragmites was unobserved or observed in small patches (<10 sq ft) at 45 sites, but half of these sites were dominated by a new invasive. Over 1/3 of species at road sites were invasive while about 1/4 of species were invasive in sites sprayed ≤3 times and when considering treatment sequence. Initial results support long-term commitments to Phragmites management and utilizing secondary techniques, such as post-treatment native plant reseeding, to counter the reestablishment of new invasive species.
Bio: Matt is WDNR's statewide wetland invasive plant specialist. He received a master's degree in conservation ecology from the University of Michigan, where he researched a restored wetland complex in the Shiawassee National Wildlife Refuge. Before arriving at WDNR, Matt worked with the USGS studying control methods for non-native Phragmites australis and writing protocols for the USFWS.