An In-Depth Look at Our Stewardship Activities at the Bear River Bottoms
by Chris Call & Mike Wolfe
Stewardship Committee members and volunteers have been actively treating invasive plant species at the Bear River Bottoms site since early March, as part of an ongoing weed management program. Of the 26 weed species identified and mapped on the 455 acre site, 7 were selected for treatment this year, based on their location and abundance, ecological impacts, and feasibility of control. Small, isolated patches are treated first, with the hope of eradicating them. For large infestations, efforts are directed at reducing plant abundance and limiting the rate of spread into uninfested areas. We use a combination of treatments, based on invasive plant life strategies and environmental concerns.
We only use chemical treatments with great care, and only when and where we feel it is absolutely necessary.
- Digging and hand-pulling (before seed set) are primarily used for biennial forbs, such as musk thistle and dyer’s woad, to prevent or drastically reduce seed production and dispersal. First-year rosettes of both species are sometimes sprayed with Escort herbicide in the spring and/or fall.
- Two perennial forbs, leafy spurge and perennial pepperweed, are extremely difficult to control due to expansive root systems with a high capacity for shoot regeneration from adventitious buds. Herbicides are applied when carbohydrate reserves in the roots are low: Plateau herbicide on fall regrowth for leafy spurge, and Escort herbicide at summer flowering for perennial pepperweed.
- Phragmites, a tall-statured, perennial grass in wetlands, is also difficult to control because it rapidly spreads by extensive horizontal stems aboveground (stolons) and belowground (rhizomes). We treated a few stands with Rodeo herbicide (approved for use in wetlands) in September, and will burn the standing dead material in late October to promote the emergence of resident native species. Surviving Phragmites stems will be treated with Rodeo herbicide in June and September in subsequent years.
- Two invasive woody species, tamarisk and Russian olive, are prolific seed producers, but they also resprout from adventitious buds on the roots and at the base of the trunk when cut or burned. We use the cut-stump method on mature trees, where the trunk is cut near the soil surface and a mixture of Garlon herbicide and methylated seed oil is immediately applied to the cut surface. When implemented in early fall, the herbicide mixture is readily transported with plant nutrients down to the roots, killing buds. After rainfall events, we use a hand tool (Uprooter) to remove saplings (including root systems) of both species.
We try to minimize disturbance as much as possible to promote the recovery of resident native species and reduce site availability for invasive species. We spread commercially available native seed on bare soil after treatment in fall/early spring.