By Jennifer Lippert and Glenn Miller
The Willamette National Forest started tracking the grass species, false brome (Brachypodium sylvaticum) in the 1990s when populations started exponentially expanding in the forest understory. This grass of Eurasian origin was initially introduced to Oregon as an accidental escapee from agronomic research plots near Oregon State University in the early 1900s. There is anecdotal evidence that it was intentionally seeded on the Willamette National Forest as a component of a wildlife forage mix for skid roads in the 1970s.
False brome and its effects on the environment are dramatic, which is why managers are concerned about its spread. It can severely reduce understory plant and animal diversity in habitats ranging from prairies in full sun to shaded conifer forests to riparian streamside habitats. It successfully competes for soil moisture with tree seedlings in plantations. Additionally, false brome thatch creates a perfect cover for voles that readily girdle young trees. Palatability for wildlife is low since it has a toxic substance that browsers avoid. It may also alter fire regimes especially where it has a dense growth of thatch.
The Willamette National Forest and Oregon Department of Agriculture (ODA) have collaborated on weed inventory and control of false brome for over 30 years. ODA and FS staff noticed false brome was dispersing along road corridors and spreading into recently harvested stands in several areas on the forest, especially the Fall Creek corridor on Middle Fork District and the Foley Ridge corridor on McKenzie River District. Treatment of these stands is difficult and expensive, because it requires crews wearing backpack sprayers to walk in parallel across the unit to find all the plants.
In 2012, ODA staff member Glenn Miller suggested that we switch from our post-harvest method of treatment, which used funds generated from the timber sale, to an aggressive pre-treatment of road shoulders. This approach was aimed at reducing false brome along travel corridors by treating areas with false brome two years prior to harvest. This would prevent seed production, so there was a lower probability that false brome seed would be transported into the unit by equipment, people, or wildlife. Following treatment, we would seed skid roads and landings with native grasses to further inhibit movement of weeds onto disturbed areas.
This method has shown great success in keeping infestations confined to road shoulders and out of recently harvested units. We are now using Stewardship and Good Neighbor Authority funding to conduct pre-treatment of road shoulders for all high-priority invasive plant species. It is much more economical because it greatly reduces our need to treat post-harvest and allows the understory to recover much more rapidly so that it can function as habitat for the native plant and animal species.
Jennifer Lippert is a botanist for the Willamette National Forest. She can be reached at 541-225-6440 or Jennifer.firstname.lastname@example.org. Glenn Miller is the NW Oregon IWM Coordinator for the Oregon Department of Agriculture. He can be reached at 541-954-8293 or email@example.com