Project to Establish Growth & Mortality Rates of Three \u3ci\u3eCarex\u3c/i\u3e Species in Two Planting Types at Thomas Dairy Site, Tigard, Oregon

Clean Water Services (CWS) currently increases the diversity of their wetland restoration projects using a plug planting method utilizing juvenile herbaceous plants. They have planted most of their projects using this method and plan to continue until a better one is discovered. According to the literature reviewed in this paper, juvenile plants are smaller and weaker than more mature plants and therefore have higher mortality rates. This paper is the culmination of work completed of phase 1 of this two-phase project. The objective of this project (both phases) was to design and establish a study that would test, in the field, two common wetland planting methods: installation of plugs of juvenile plants at a relatively high density and installation of containerized, more mature plants at a lower density. This study will examine three species of Carex frequently used in wetland restoration (Carex stipata, C. obnupta, and C. unilateralis) and compare the growth and mortality of mature versus juveniles of these species within Thomas Dairy Site in the Tualatin River Watershed. For phase 2, at Thomas Dairy Site, 13 randomly selected plots will each contain six subplots including a subplot planted with monocultures of each of the three plants, and two sizes (i.e., mature C. stipata, juvenile C. stipata, mature C. obnupta, juvenile C. obnupta, mature C. unilateralis, and juvenile C. unilateralis). These will be monitored for five years, during which mortality rates will be recorded once a year and total percent cover recorded three times a year. I hypothesize that the mature plants will have a higher percent cover after five years because juvenile plants are more susceptible to die over that timeframe and may have slower growth rates overall. Answering these questions will allow CWS and other wetland restoration managers to achieve greater plant coverage, reduce waste, and reduce costs