Date of Graduation

Spring 5-15-2020

Document Type

Project/Capstone

Degree Name

Master of Science in Environmental Management (MSEM)

College/School

College of Arts and Sciences

Department/Program

Environmental Management

First Advisor

Aviva Rossi

Abstract

California’s valley grasslands are one of the most invaded ecosystems in the state. It is estimated that valley grasslands contain between 90 to 99% cover of non-native plants. The most recent wave of invasive plants has included medusahead (Elymus caput-medusae L.). Medusahead is an annual grass that matures two to four weeks later than most other grasses. Management of medusahead includes the use of herbicides, targeted grazing, prescribed burns, and mechanical control. The primary focus of most studies on the use of these management methods is on the control of medusahead rather than the impacts on non-target plants. This study examines published research to determine what impact medusahead management has on the composition of plant communities within valley grasslands. Herbicides have mixed impacts on the percent cover of grasses and forbs. Targeted grazing resulted in decreased percent cover of non-native grasses and increased forb cover. Grazing results in neutral to increased percent cover of native plants. Prescribed burns decreased the percent cover of non-native grasses, increased forb cover, and had mixed impacts on native plant cover. Mechanical control shifted vegetative states towards forb or filaree (Erodium spp.) dominated communities. The non-target impacts of medusahead control were generally short-lived with differences in percent cover returning to baseline conditions within one to three years. To mitigate the non-target impacts of medusahead, revegetation efforts should be prioritized in sites with higher abundances of native plant species. The future success of controlling medusahead is dependent upon grassland restoration research, consistent funding for weed management areas to aid in managing invasive plants, and the implementation of monitoring after medusahead control treatments.

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