Establishment of Wildflower Islands to Enhance Roadside Health, Ecological Value, and Aesthetics

Authors

Jackson Ebbers, University of Nebraska-LincolnFollow

First Advisor

John Guretzky

Date of this Version

5-2024

Document Type

Thesis

Citation

A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Masters of Science

Major: Agronomy

Under the supervision of Professor John Guretzky

Lincoln, Nebraska, May 2024

Comments

Copyright 2024, Jackson Ebbers. Used by permission

Abstract

Roadsides provide an abundant opportunity to increase connectivity of fragmented landscapes with diminishing floral resources for pollinating insects. The ecological value of these sites is often overlooked as quality habitat for pollinators, particularly monarch butterflies, which have been experiencing severe declines due to loss of habitat and loss of milkweeds that provide food for their larvae. Land managers across the nation are realizing the potential of roadsides to provide high quality floral resources for the benefit of insects and other wildlife. Current wildflower seed mixes used by state transportation departments are often low diversity and may only be implemented following road construction with no follow-up management. Mowing is often used on roadsides to manage vegetation for safety and aesthetic reasons. The timing and frequency of mowing can impact the density and diversity of wildflowers present on a site. This research seeks to determine the efficacy of seeding a diverse, native wildflower seed mix into backslopes with well-established perennial grasses. We monitored two sites in southeast Nebraska in 2021 and 2022. Two mowing regimes: October pre-seeding mowing and July post-seeding mowing were studied to determine the effects that mowing may have on existing perennial grasses. Our results indicate that seeding wildflowers is effective at increasing wildflower density, diversity, and floristic quality of a site. Milkweed abundance also increased because of seeding. Mowing dormant vegetation in October before seeding appears to increase forb cover and floristic quality of one site, particularly in the first season after planting. This benefit of pre-seeding mowing appears to stem from a reduction in vegetative litter in the plots. Post-seeding mowing provided no benefit to wildflower density or diversity. Neither mowing treatment led to a reduction of perennial grass cover by the second season of the study, confirming that grasses can recover quickly following disturbance. The temporary reduction of litter following October mowing, however, may enable forbs to germinate in the spring following seeding.

Advisor: John Guretzky