PARENT SESSION
Oral Session 133: Grasslands V: Grazing.
Presiding: E Fredrickson
Friday, August 6, 8:30 AM to 12:00 PM, Meeting Room B 117.
Using herbicides and native seeding to restore grasslands infested with the invasive plant Potentilla recta.
Endress, Bryan*,1, Parks, Catherine2, Read, Bridgett2, 1 Forest Science Department, Corvallis, OR, USA2 US Forest Service, La Grande, OR, USA
ABSTRACT- Invasive plants drastically impact grasslands and cause a loss of native plant communities, wildlife habitat, and productivity. For decades, herbicides have been integral to weed management, for example, in 1997, of the 988 million acres of U.S. grasslands, 25% were treated with herbicides. However, herbicides alone are rarely successful in controlling weeds over time. In the short term, herbicides may reduce invasive species abundance but without further restoration activities, areas are often colonized by other invasive species. Few studies explore the impact of herbicide application on native plants; thus, management guidelines that integrate invasive species control with habitat restoration are needed. We evaluate methods to restore grasslands dominated by the invasive perennial Potentilla recta. Our objectives were to identify which herbicides, at what rates and what time, are most effective in controlling P. recta, while having reduced impact on existing and planted native grasses. We used a randomized complete block split-plot design applying six herbicides at two rates and three application periods with two levels of post-application seeding of native grasses. Results after one year showed that herbicides were effective at reducing P. recta abundance. Control varied depending on the herbicide, rate, and timing. However, all herbicides reduced native species richness, while richness of non-native species was unchanged. Results show that while herbicides may succeed in controlling target species, use should be carefully planned as part of a broader strategy for controlling invasive species. Longer term monitoring will demonstrate the significance of herbicide and seeding treatments in restoring native grasslands.
Key words: rangelands, eastern oregon, sulfur cinquefoil, herbicide screening