Tall Oatgrass Ecological Impact Study

Early seed filling stage of Tall oatgrass

Tall oatgrass ( Arrhentherum elatius) is a non-native cool season bunchgrass from Europe that is found in many grassland systems across the United States. While the species is fairly sensitive to heavy grazing pressure, it can become invasive, replacing valuable native species and altering grassland habitat and heterogeniety.  In the grassland ecosystems surrounding the City of Boulder, tall oatgrass populations have expanded rapidly, creating monocultures that overtop and outcompete native tallgrass species, reducing habitat quality in an imperiled grassland type.

Dispersal Risk Map
Estimated risk of tall oatgrass expansion in Boulder over the next 10 years.

To address the issue, EnviroPlan Partners was contracted by the City of Boulder Open Space and Mountain Parks (OSMP) to  to develop a strategic and comprehensive approach for managing the species.  For this project, EPP worked with Boulder OSMP to study tall oatgrass and develop tools and strategies for controlling the species.  EPP prepared a literature review to look at population dynamics and biological attributes of tall oatgrass, along with background on potential treatment options and impacts to wildlife.  EPP also facilitated and organized one-on-one discussions and a webinar with natural resource experts, researchers, and land managers from across the country to get first hand information on the concerns and needs for managing tall oatgrass in different ecological systems.  EPP worked closely with the City of Boulder to develop a spread risk model to estimate potential habitat and spread rate based on ecological indicators.  The risk model estimates the potential rate of spread in areas with similar habitat to where tall oatgrass currently occurs in Boulder for the next 10 years.

Cattle used by the City of Boulder to control tall oatgrass

Based on the findings of the literature review and discussions with experienced natural resource professionals, EPP studied a variety of potential treatment methods for treating tall oatgrass.  This included an indepth feasibility study of each proposed method and the potential impacts to resources of concern, including grasslands, forests, recreation, wildlife, water, and occurrence of natural disturbance regimes.  EPP then developed a 10-year management plan with recommendations for the most effective treatment methods.  These methods include the use of cattle grazing, controlled herbicide applications, mechanical removal, and manual removal options.  The management plan serves as a starting point for more targeted action to reduce the spread and cover of tall oatgrass while continuing to enhance the valuable ecological processes of tallgrass communities in the Boulder area.  Together, the ecological study will be used by OSMP to develop an implementation plan to begin treating specific tall oatgrass populations as part of a concerted effort to reduce tall oatgrass cover on these valuable tallgrass prairies.  Use the link below to learn more about this project.

City of Boulder Tall Oatgrass Ecological Impact Study

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