Comparing Himalayan blackberry (Rubus armeniacus) management techniques in upland prairie communities of the W.L. Finley National Wildlife Refuge

Graduation date: 2015Dedicated to the preservation and promotion of many of the nation’s most threatened and endangered species, the W.L. Finley National Wildlife Refuge is highly invested in the management of some of the last remaining upland prairies once prevalent throughout Oregon's Willamette Valley. More than a century of land fragmentation, fire suppression, and cultivation has shifted species composition and physical structure of the native prairies toward woodland ecosystems, reducing habitat quality and quantity. This transition is greatly driven by the encroachment and introduction of the non-native, woody invader Himalayan blackberry (Rubus armeniacus).\ud This study focused on the three most common Himalayan blackberry management techniques used within the refuge's upland prairies: late summer mowing, late summer burning, and a combination of both. The goal was to analyze the efficacy of each technique in meeting the refuge objectives of controlling Himalayan blackberry populations and promoting native prairie physiognomy after one application using a complete random block design. Findings were presented to refuge managers to facilitate improved management of these fragile communities.\ud Mowing was found to have the greatest reduction in blackberry stem and plant density and resulted in the lowest resprout density post-treatment. This treatment also met the refuge objectives of reducing woody cover and increasing graminoid cover, but did little to increase herbaceous cover when compared to the control group. Burning produced no significant increase in herbaceous cover or reduction in woody cover and provided favorable conditions for Himalayan blackberry seedling germination, contributing to a larger blackberry problem in years to come. In promoting herbaceous habitat for upland-dependent species, mowing with subsequent burning was the most successful technique. Though not as effective in reducing blackberry vigor as mowing alone, this treatment showed the most potential of the three in managing for all objectives