Willamette Mission Floodplain Reforestation and Aquatic Invasive Control, Phase 6

Willamette Mission State Park (Marion County, near Salem-Keizer) forms the southern extent of what is currently the largest tract of intact, reproductive floodplain forest in the Willamette Valley. On acres that are hydrologically connected to the Willamette River, the project will remove invasive weeds that have replaced and now inhibit natural forest regeneration,and affected in-stream habitat conditions. Phase 6 funding will be used to treat aquatic invasive plant species in Windsor Slough (85 net acres) and also focus on treatments along the riparian zone adjacent to the mainstem Willamette River and Mission Lake (50 acres). Trained, certified contract crews will control both terrestrial and aquatic invasive weeds. Primary project partners include: Willamette Riverkeeper, Oregon State Parks, Department of State Lands, Windsor Rock Products, local farmers who are private landowners, Integrated Resource Management, Ash Creek Forest Management, Oregon Watershed Enhancement Board, Meyer Memorial Trust, Bonneville Power Administration, Marion Soil and Water Conservation District, and local community members.

Because the projects scheduled end date is after the PCSRF FFY 2019 award closes, no funds allocated for this project are reported as match to PCSRF funds.

In addition to benefiting many species of native fish and wildlife, the project will also benefit listed fish. The project is expected to improve overall water quality, which will benefit listed fish, in two ways: 1) through reforestation which increases shade, nutrient exchange, and groundwater infiltration of floodwaters; and 2) through aquatic invasives control which we expect will improve water quality conditions. Aquatic invasive species such as Ludwigia have been shown to impact water temperature, reduce dissolved oxygen, cause increased sulfide and phosphate, reduce pH, and produce allelopathic chemicals that can negatively affect fish and invertebrates (which form the food base for juveniles). Ludwigia displaces native riparian forest along slough margins, impacting shade and wood recruitment. The changes to water chemistry and native aquatic plants from Ludwigia dominance impact macroinvertebrate density and diversity, which directly impact listed fish by reducing food quality and quantity. Ludwigia accelerates sedimentation rates, creating shallower habitat over time, and in winter root masses underwater resist scour during floods. Invasive aquatics have even been shown to increase populations of non-native fish, which can impact listed fish through competition and predation. Ludwigia control at this site not only benefits the site, but reduces risk for high quality fish habitat downstream which can be infested with Ludwigia due to propagules moving downstream from Windsor Slough, including important cold water refuges at Spring Valley, Wheatland Bar and at the mouth of Lambert Slough. The Ludwigia and floodplain reforestation portions of the project addresses the following categories of threats, described in the Recovery Plan (ODFW/NMFS 2011) as follows: Other species: “Effects of other species include predation and competition effects by native and non-native fish, or other animals, and habitat degradation effects by non-native plants.”; Water quality: “Water characteristics including temperature, dissolved oxygen, suspended sediment, pH, toxics, etc.”; Physical habitat quality: “Habitat characteristics include floodplain connectivity and function, channel structure and complexity, channel morphology, riparian condition (including loss or alteration of stream habitat) and large wood recruitment, sediment routing (fine and coarse sediment), and upland processes.”; Food web: “Changes in the food web…”[e.g. macroinvertebrate and native plant fo