Drift Creek Restoration Monitoring

Drift Creek Restoration Monitoring USFWS By Terra M. Hauser U.S. Fish and Wildlife Service Oregon Coast National Wildlife Refuge Complex 2127 SE Marine Science Drive Newport, Oregon 97365 September 2019 EXECUTIVE SUMMARY In March 2019, over 1,000 native trees and shrubs were planted in the Siletz Bay National Wildlife Refuge. The planting site, known as the Drift Creek Gorton Road Unit, is located between a privately-owned pasture and Drift Creek, with a levee separating the pasture from the creek. The goal is to create a riparian buffer zone along this levee and improve wildlife habitat. Establishing this riparian zone is only one component of a larger project to enhance and restore fish and wildlife habitat in and along Drift Creek. Other tasks to achieve this purpose include widening the historic wetland channels, strategically placing large woody debris along the banks to create log jams, and removing the levee to restore floodplain connectivity and the natural flow of the creek. When the levee is removed, the buffer can trap woody debris during flooding and prevent damage to the neighboring private land. The trees and shrubs in the buffer zone, as well as any woody debris that may get trapped among them, will provide habitat for fish, wildlife, and invertebrates in the process. In addition, the vegetation in the buffer zone will play an important role in improving water quality in Drift Creek, including by providing shade to decrease the water temperature, stabilizing the banks to reduce erosion, and catching agricultural runoff, preventing it from contaminating the creek. The riparian buffer will be completed in five phases, of which the 2019 planting was the first. To prepare the site for this task, an animal exclusion fence was built to reduce the risk of browsing; most trees and shrubs were planted inside this fenced area. In August 2019, a monitoring team revisited the planting site to evaluate first year survival, health, and growth of each species. The results indicated the survival rate of trees and shrubs inside the fence was higher than that in a control row planted outside the fence, where plants had been grazed and trampled. The lowest survival rate inside the fenced area was vine maple (Acer circinatum) at 4.0%, followed by red elderberry (Sambucus racemosa) at 42.1%. Two other species achieved 100% survival. On the other hand, outside the exclusion fence, the lowest survival rate was red-osier dogwood (Cornus stolonifera) at 25%, while three species, all of which had one individual planted, achieved 100% survival. Likely the most significant threat facing the plants inside the fenced area is competition, particularly from the invasive reed canarygrass (Phalaris arundinacea). Many trees and shrubs died among dense patches of reed canarygrass, and even more were not found at all. In the future, both mechanical and chemical means of controlling invasive species prior to and after planting will be employed. i BACKGROUND Estuaries are some of the most productive habitats in the world, hosting thousands of species of plants, animals, and insects (National Oceanic and Atmospheric Association 2019). They are known as nurseries due to their importance to many species at various periods of their life cycle; namely, juvenile Pacific salmon that spend more time in estuaries tend to have higher survival rates than those that do not (Bonneville Power Administration and US Army Corps of Engineers 2013). However, the quality of the estuary can have a significant impact on the survival rate of salmon, and some studies even suggest that salmon that develop in more natural or restored estuaries have up to three times the survival rate of those that develop in estuaries in poor condition (ibid.). Since the 19th century, development has contributed to the tidal marsh ecosystem in Siletz Bay declining by nearly half (USFWS 2013). In particular, agriculture, logging, and urban expansion have negatively impacted native salmon runs through habitat degradation including widening channels to allow large logs to travel downstream and destroy spawning grounds, and increasing runoff and erosion by removing buffer vegetation (Sedell et al. 1991). Meanwhile, Coho salmon (Oncorhynchus kisutch), an indicator species, had once experienced runs of up to 2 million along the Oregon Coast as recently as the early 1900s, but the numbers have since dropped to 57,000 in 2015 (National Marine Fisheries Service 2016). To combat the effects of habitat degradation, the Siletz Bay National Wildlife Refuge is beginning a restoration project that aims to restore and enhance historical salmon habitat (Spann 2018.). Ultimately, the goal of the restoration project is to remove the levees that are blocking historical salmon habitat, restore natural floodplains and tidal exchanges, and widen channels (ibid.). This project will take place on several parcels of refuge property, one of which is the Drift Creek Gorton Road Unit. The Gorton Road Unit is a parcel of the Siletz Bay National Wildlife Refuge located between Drift Creek and private farmland. A levee constructed between 1945 and 1952 separates the creek from the pasture used for cattle grazing. The first phase of the restoration project is to establish a riparian buffer between the private land and the creek. When the levee is eventually removed, the buffer will prevent erosion and block woody debris from entering and damaging private land (National Agroforestry Center 2012); this woody debris can also be beneficial to the creek and the buffer zone by providing shade and habitat for animals and insects (Hawkes and Smith 2005). Other benefits to creating a riparian buffer include higher water quality from vegetation soaking up harmful substances before they reach the creek, lower water temperatures from tree canopies providing shade, and bank stabilization from the roots (National Agroforestry Center 2012). The recent planting in March 2019 marks the first of five phases in creating a full riparian buffer. We hope to use lessons learned from monitoring this first section to improve subsequent sections of the buffer and ultimately contribute to a healthy ecosystem. METHODS On 27 and 28 March 2019, the Oregon Coast National Wildlife Refuge Complex staff, interns, and volunteers planted over 1,000 native plants in a pasture in the Siletz Bay National Wildlife Refuge along Drift Creek (Figure 1). Several species were planted at the site, including: western redcedar (Thuja plicata), Sitka spruce (Picea sitchensis), salmonberry (Rubus 1 spectabilis), cascara (Rhamnus purshiana), western hemlock (Tsuga heterophylla), Hooker’s willow (Salix hookeriana) and unknown willow cuttings (Salix spp.), twinberry honeysuckle (Lonicera involucrata), red elderberry (Sambucus racemosa), red alder (Alnus rubra), Oregon crabapple (Malus fusca), vine maple (Acer circinatum), and red-osier dogwood (Cornus stolonifera). Salmonberry, Hooker’s willow, twinberry honeysuckle, red elderberry, red alder, Oregon crabapple, and vine maple were bare root plants. Western redcedar, Sitka spruce, and western hemlock were planted from containers. Red-osier dogwood and the unknown willow species were cuttings obtained by a volunteer. Several measures were taken to aid the plants in getting established. Despite the small size of the site (Figure 1), there are several vegetation profiles and different elevations that affect water levels. Therefore, each species was planted strategically based on flood and drought tolerance. Another challenge of this site is that it is located within a cow pasture where elk are also known to graze, so to protect plants from damage from browsing, an animal exclusion fence was built. The majority of trees and shrubs were planted within this fence, but to test whether an exclusion fence is necessary for future phases of the project, a control row was planted along the outside of the fence (Figure 1, Figure 2). There are also several species of both native and invasive grasses, rushes, and other low-elevation plants that grow very tall and fast, so new plants would face significant competition. Rather than planting each tree or shrub randomly, we planted in rows so that refuge maintenance staff could mow the site to remove competitor species. To control the competition and give new plants a chance to grow, refuge maintenance staff used herbicide to kill existing competitor species along these rows. They also periodically visited the site to mow between the rows. In addition, staff, interns, and volunteers visited the site to identify and control invasive species. After the planting was completed, a map was created to show where each individual plant was located to assist in the monitoring effort. The map divided the area inside the exclusion fence into ten grids in equal distance from each other (Figure 2). In August 2019, a monitoring team visited the site to evaluate the plant growth and health. Using the maps, they were able to find the majority of the plants within the rows. They classified each plant as alive, alive but stressed, or dead (Table 1, Appendix 2). Plants were marked as alive when they showed obvious signs of life such as new growth, or when the stems were still pliable rather than stiff and brittle (Cook-Patton et al. 2014). The height of each plant was also measured and recorded in the reference sheet in Appendix 1 to establish a baseline to track growth in the future. Finally, photos were taken of each grid from the northwest corner of the grid facing the southeast corner (Appendix 3-12). To analyze the data, the survival rate of each species was calculated with the following equation. = × 100 The survival rate equation assumes that the plants the monitoring team could not locate had died. However, without observing a plant, the monitoring team could not determine if it was alive or dead. Since there were several plants that were simply not found through dense vegetation, the actual survival rate could be higher.

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