Prescribed cattle grazing as a tool for native prairie management: Lessons from the Tualatin River basin, Oregon

Land managers of prairie and savanna sites in the Willamette-Puget Trough-Georgia Basin (WPG) ecoregion are tasked with reestablishing native species, managing the threat of invasive species, and encouraging or introducing regular disturbance regimes to maintain ecosystem function.  Historic disturbance regimes included anthropogenic burning and grazing by native ungulates. While fire remains critical from an ecological perspective, a number of climatic and logistical barriers exist in places like the urban-fringed and populated Tualatin basin.  Using cattle to manage native prairie is a growing tool and area of study in the WPG.  With cooperation and support from the Wildlife Conservation Society Climate Adaptation Fund, Tualatin Riverkeepers, landowners, and cattle operators, we grazed and seeded two Tualatin basin prairie sites during 2016 and 2017.  The goal of grazing was to create disturbance and improve diversity and composition of the native herbaceous plant community.  We captured baseline vegetation conditions before grazing and tracked change in height and percent cover of vegetation groups as a result of grazing.  Cattle provided the necessary disturbance to both prairies to facilitate a change in height of vegetation during the grazing period, however results in percent cover of bare ground and thatch/litter differed between sites.  After one year, native forb cover increased, as did non-native forb cover.  In addition to preliminary ecological data, we discuss challenges, successes, management implications, and the importance of partnerships in implementing this type of program.