Date of Award

January 2017

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Susan N. Ellis-Felege

Second Advisor

Daniel Svedarsky

Abstract

Wetlands in the United States have been considered both an impediment to progress and a valuable asset for ecosystem services. As a result, rapid loss and degradation of wetlands has occurred and many attempts to protect and restore wetlands are now occurring. However, invasive species continue to challenge wetland management efforts. Cattails (Typha spp.) are invasive plants that can dominate a wetland once they become established. There are two species of cattails in the Northern Great Plains, broad-leaf (Typha latifolia) and narrow-leaf (Typha angustifolia) cattail. These two species can cross to produce a robust, hybrid cattail (Typha x glauca) that has become an increasing problem in wetlands. Over time, they can make the wetland become “cattail-choked”, excluding many native plant and wildlife species. Therefore, we sought to answer the question of what management techniques used to control cattails not only reduce them, but also which methods benefit both native plants and wildlife. Our study focused on 23 shallow wetlands at Glacial Ridge National Wildlife Refuge in northwestern Minnesota. We explored the effects of the treatments mowing, fire, chemicals, and the combination of chemical x fire on reducing cattails and promoting native flora and fauna. We collected baseline information in the summer of 2014 followed by management applications in the fall of 2014 and then two years of post-treatment data were collected in 2015 and 2016. We found that the use of chemicals (glyphosate) reduced the percentage of live cattail, while fire increased the percentage of live cattail. All other species of vegetation were impacted negatively by chemical x fire and little by the other treatments. Overall bird species richness was not influenced by the treatments, likely due to some species benefiting from the treatments, while others did not. We analyzed the response to treatments of five individual bird species, marsh wren (Cistothorus palustris), sedge wren (Cistothorus platensis), swamp sparrow (Melospiza georgiana), red-winged blackbird (Agelaius phoeniceus), and common yellowthroat (Geothlypis trichas). Marsh wren abundance decreased following the use of chemical and fire. Sedge wrens increased after fire. Swamp sparrows generally benefited from all of the treatments. Red-winged blackbird abundance decreased after the use of chemical, but increased after chemical x fire was applied. Common yellowthroats decreased one-year post-treatment followed by an increase two- years post-treatment. Amphibian species richness was not impacted by the treatments. Boreal chorus frog (Pseudacris maculata) abundance did not change relative to treatments; however, we did observe an increase from mowing. Dragonfly and damselfly abundance was not impacted by the treatments statistically. We did, however, observe a percent decrease after fire and chemical x fire for dragonflies. Our results show the best control method for reducing cattails is a combination of fire and chemical; however, the wetland system is complex with members of the community impacted differently by different treatments.

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