Planting Vegetation for Fish and Wildlife
The Trinity River Restoration Program has been working to create quality fish and wildlife habitat at its channel rehabilitation sites by releasing the river from its straightened condition (confined by vegetation and historically high banks) and allowing it to create complex habitat within its floodplain. This is done by lowering the floodplains so they are inundated with water more often, opening up the river banks, and adding gravel in selected locations.
This rehab work requires removal of much of the riverine vegetation on the banks and floodplain, yet this vegetation (e.g., willows and cottonwoods) is integral to creation of good fish and wildlife habitat. So, we save the big trees where we can and replace the vegetation lost during construction. This is done using a combination of mechanical planting and by creating conditions that encourage natural recolonization. The replanting is a joint project between the Trinity County Resource Conservation District (RCD) and the TRRP and occurs in the wet months following the project construction.
To ensure a natural diversity of plants recolonizes the constructed channel rehab sites mature trees are preserved as seed sources. These preferred "save trees" are the relatively rare and tall “tree type” willows (e.g., red and shiny willow species) and cottonwoods. Additionally, cuttings from a diversity of native riverine trees are planted and natural seed beds (e.g., small depressions and logs left on the floodplain) are left to capture drifting seeds and encourage natural riparian regeneration. To enhance these sites even further, wetland plant species like sedges and rushes (and various willow species) are also being planted on the edge of side channels and wetlands. Altogether, these plants will provide important shelter and food for fish and wildlife, especially when the high flows wash bugs from these plants into the river and side channels.
While channel rehab sites are quick to construct, we are testing various techniques to efficiently and quickly restore disturbed areas for fish and wildlife use. In fall 2008, at the Forest Service’s Sven-Olberston Rehab site near Lewiston dam, a pond behind the weir was drained, the flood-plain lowered, and several side channels were created. Already in February 2009, spawning steelhead and chinook salmon juveniles were using the new side channels. The RCD has now planted sedges in the area. They used a backhoe to plant pole cuttings of relatively rare riverine species deep enough so they will remain in contact with wet soils. These plantings were placed on the edges of the side channel so they can soon provide cover for juvenile fish which are already using the area. The RCD also seeded the floodplain throughout the Lewiston project area, with inundation tolerant species of rye and barley that will grow to enhance wildlife habitat for years to come. If you start to visit the river near Lewiston now, you too may watch as these recently constructed channel rehab sites develop and grow to maturity.