Post-Treatment Monitoring of Typha Management

Abstract

Typha angustifolia L. and Typha × glauca Godr. (Typha) are aggressive non-native invaders of wetlands in the Midwestern United States. Typha forms dense stands through rhizomatous expansion, resulting in prolific biomass and litter production that have a mulching effect on competing vegetation. Typha invasions reduce species richness, diversity, and floristic quality in wetlands. Typha is widely distributed throughout southeastern Wisconsin’s Mukwonago River watershed, where it has invaded species-rich wetlands owned and managed by The Nature Conservancy’s Mukwonago River Watershed Project. The Nature Conservancy initiated active Typha management in these wetlands beginning in 2015. The ecological restoration goals were to reverse the Typha invasions and restore wetland plant communities to their pre-invasion condition. Typha management consisted of coupling periodic prescribed burning (for litter removal) with selectively targeted applications of imazapyr herbicide. In 2020, we surveyed plant species composition in three managed, two unmanaged, one transitional, and two reference wetland stands, then subjected the species composition data to classification and ordination. Our monitoring data showed that plant species assemblages in managed stands were compositionally more closely aligned with the target communities represented by reference stands than they were to unmanaged stands. We conclude that Typha management in these wetlands was accomplishing restoration goals and has led to improvements in species richness and floristic quality in fen wetlands.