Willamette Mission Floodplain Reforestation, Final Phase 7

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. This proposal is for the 7th and Final Phase of the Willamette Mission Floodplain Reforestation project. Restoration actions will focus on acres that are hydrologically connected to the Willamette River. This project will focus on removing invasive weeds that inhibit natural forest regeneration and re-establishing diverse, resilient floodplain plant communities to benefit diverse species of native fish and wildlife. This approach seeks to protect the best in the Willamette basin, preventing loss of this critical habitat. Native plants will be installed where needed; and trained, certified contract crews will control mow and spray invasive weeds as part of plant establishment treatments in riparian zones from this and previous phases of the project. This project will also engage local community members in on-site stewardship activities. Plant stewardship activities (reported as C.11 - Site Maintenance) will be conducted for up to four years after the plantings are completed. The stewardship activities will ensure the success of the project plantings by helping plants achieve free-to-grow status. Partners for this comprehensive project include Willamette Riverkeeper, Oregon State Parks, OWEB, Meyer Memorial Trust, Bonneville Power Administration, U.S. Fish and Wildlife Service, R. Franco Restoration, Integrated Resource Management, Ash Creek Forest Management, Cascade Environmental Group, One Tree Planted, Promise the Pod, U.S. Geological Survey, Portland State University, North Salem High School, DSL, and several private landowners and farmers.
Because the projects scheduled end date is after the PCSRF FFY 2020 award closes, no funds allocated for this project are reported as match to PCSRF funds.

Many of the benefits of floodplain reforestation can be visualized by picturing floodwaters spread across a farm field to floodwaters spread across a dense, native forested floodplain. Heterogeneity in floodplain vegetation communities provides a mosaic of food webs, which are utilized by anadromous salmonids and important to their recovery and persistence (Bellmore et al. 2013). Forested floodplains provide seasonal shallow-water refuge for juvenile fish, allowing them to rear and conserve energy (Hafs et al. 2014). Vegetated shallow-water habitat provides more complex and heterogeneous cover for small Chinook salmon and steelhead to hide from predators and a higher abundance of terrestrial and aquatic insects that form the bulk of their diet (Hafs et al. 2014). Dense, mature native forests contribute large wood to areas downstream, providing year round habitat complexity.

Native fish also benefit from floodplain forests via improved water quality. The maturing forest established through this project will improve water quality by trapping nutrients, sediment bound pollutants and fine sediments (Johnston 2009). Floodwaters entering the dense forest will slow and be captured onsite, allowing water to infiltrate into historic floodplain deposits (cobble, gravels, and clay soils) and may be available to return to the river as hyporheic flow in warmer months when high water temperature and low flow stress cold water fish (Williams 2005). Nutrient cycling is supported as the seasonally inundated forest receives and interacts with floodwaters, contributing fine organic matter to the main-stem Willamette.

Specifically for listed Chinook salmon and steelhead, the floodplain reforestation portion 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.
* 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. nutrient cycling and sources of insects]

The limiting factor identified in the Recovery Plan that applies to the mainstem Willamette, and that floodplain reforestation will help address, is: Physical habitat quality (impaired habitat complexity and diversity): land use practices including stream cleaning, straightening and channelization, revetments, riparian area degradation, lack of large wood recruitment, and/or loss of floodplain connectivity and access to off-channel habitat.

Some of the actions the Recovery Plan recommends for the mainstem Willamette, which would be accomplished by the floodplain reforestation portion of the project, are: restore priority non-functioning wetlands, restore natural riparian communities and their function, and restore structure and function to strategic natural riparian reaches in the mainstem Willamette River.

The goal of the Willamette FIP program is to sustain and enhance seasonally important resources for native fish. The primary benefit of floodplain reforestation is experienced by native fish when the floodplain is activated (flooded) in the winter and early spring. However, additional benefits during the summer include promotion of groundwater infiltration that may return to the river in summer as cold water hyporheic flow, through provision of large wood that benefits native fish year round, and through direct shading along riparian edges.