Invasive Plant Species and Their Impact on Stream Health using Macroinvertebrates in the Willamette Valley, Oregon

Abstract

Oregon spends approximately $83 million annually to maintain invasive plant species, which decreases resource availability for the environment and humanity. Their continued spread affects riparian zones, one of the most biologically diverse ecosystems that supplement stream and upland habitats. Some of the energy flow in these systems circulates by macroinvertebrates that decompose leaf litter during their immature stage of life. Upon metamorphosis, they rely on plants in riparian zones for reproductive habitat, making them prey to predators in stream and upland food webs, referred to as a transformational link. This research examines how invasive plant species affect stream health in sites of different urbanization statuses. A biological assessment evaluates the conditions in our selected Willamette Basin streams: Johnson Creek, Carver Park, and Metzler Park. The macroinvertebrate Community Science- Indices of Biologic Integrity scoring system (CS-IBI) evaluates stream health impairment. Plant collection requires using a quadrat, transect tape, and various identification tools. Our results show impaired stream health in areas with higher invasive species coverage. A significant limitation of this research is the co-variance with urbanization. There is a need for better prevention methods and specific research on how invasive and noxious species impact biota.