DESCRIPTION
Asotin Cr supports wild summer steelhead and is the location of an Intensively Monitored Watershed (IMW). The IMW focuses on 3 tributaries in the upper portion of the watershed: Charley Cr, NF Asotin Cr, and SF Asotin Cr. The primary limiting factor identified in the IMW and other watershed assessments are associated with RIPARIAN FUNCTION (e.g., temperature, habitat quantity & quality). The goal of this project is to improve riparian function by weed control and planting native tree species. The focus areas will be the lower 8 km of Charley Cr, the lower 1-3 km of NF Asotin Cr, and km 5-6 of SF Asotin Cr. The direct benefits to steelhead and other species in Asotin Cr will be improved riparian function on a more sustainable basis than the direct instream actions conducted under the IMW, which were intended as a temporary habitat improvement. This project would promote long-term riparian function by speeding the recovery of a more natural and native dominated riparian and floodplain vegetation community. The restoration will especially lead to an increase in frequency of tree species such as Douglas-fir, ponderosa pine, and cottonwood that achieve a large enough size that when they fall into the stream or floodplain area have the ability to influence channel dynamics and will increase the diversity of habitats available for all freshwater life stages of steelhead and other fish species using Asotin Cr. This is the final phase of the IMW Restoration.
The Asotin Co Conservation District (ACCD) planted and maintained riparian vegetation along 1.16 miles of the highest priority areas of the Asotin Creek Intensively Monitored Watershed (IMW) in southeastern Washington. The primary limiting factor identified in the IMW is limited riparian function (e.g., temperature, habitat quantity and quality). The goal of other restoration work being conducted in the IMW is to improve riparian function by increasing channel-floodplain connectivity. This project supports that goal by speeding the recovery of a more natural and native vegetation community as riparian conditions improve. The project objectives were to improve riparian function and increase stream dynamics for fish habitat by providing vegetation that will eventually make its way into the stream as large woody debris.
In the spring of 2016, the ACCD planted nearly 4,000 native trees and shrubs in 12 sites containing 7.3 acres along the riparian corridor of the South Fork of Asotin Creek and Charlie Creek. Both streams are known to contain populations of threatened and endangered fish, including steelhead and Bull Trout. ACCD considered riparian restoration along the North Fork of Asotin Creek, but the riparian vegetation was in better condition than the other sites that were planted and, therefore, was a lower priority and not planted as a part of this project. Five of the 12 sites contained strips of landscape fabric, into which trees and shrubs were planted, to aid with weed control and moisture retention. Of the total number of stems planted, 30% were placed in landscape fabric strips and 70% were planted in open ground. Landscape fabric strips were placed in the fall of 2015. Prior to applying fabric, the area directly under the strips were rototilled to loosen soil and aid in moisture absorption and retention.
Sites locations were chosen based on areas within the riparian containing enough soil to support tree & shrub establishment. Trees and shrubs were planted throughout the riparian zones, beginning at the streambank toe and extending through the floodplain and into the lower upland zone in several sites. Trees were planted in dense spacings of approximately 9 X 9 square feet per tree. No protection nets or tubing were installed. Cottonwood cuttings were placed in the stream at water’s edge in places where soil was available.
The ACCD tracked tree survival by species and by site location for the 2016 and 2017 growing seasons. A complete site visit to collect mortality information was done at the end of each growing season before plants entered dormancy stage.
Trees and shrubs in 11 of the 12 planting sites were irrigated throughout the 2016 and 2017 growing seasons by means of a drip irrigation system connected to a water truck. Site # 10 on Charley Creek was excluded form watering due to lack of access to turn the water truck around. Each tree received a minimum of 1 gallon of water per watering to establish root systems and increase survival from May to September of the growing season. Trees were watered once per week in May to mid-June until weather conditions get hot and dry enough to warrant watering each tree one gallon twice per week.
After the first growing season, it bacame apparent that competing vegetation must be controlled in open ground planting areas without landscape fabric. Asotin County Noxious Weed Control Board, Washington Department of Fish and Wildlife, and the ACCD cooperatively developed a weed management plan for the planting sites. The plan contained detailed maps of site locations, an herbicide guide, a backpack calibration guide, a cheat sheet for herbicide mixtures, alternative control methods and information on individual weeds found in the survey area. All 12 sites and the perimeter around the planting areas were spot treated with herbicide 3 times, in the fall of 2016, spring of 2017 and again in the fall of 2017. Weed control will be performed by Washington Department of Fish & Wildlife in the spring of 2018 and thereafter.