Upland Prairie Restoration Research at Wild Iris Ridge
This project aims to identify and test best practices for upland prairie restoration in the Willamette Valley where management tools (such as prescribed burning) might be limited. Sites along Wild Iris Ridge were selected
This project aims to identify and test best practices for upland prairie restoration in the Willamette Valley where management tools (such as prescribed burning) might be limited. Sites along Wild Iris Ridge were selected to receive site preparation treatments followed by management treatments based on the methods of several long-term restoration projects in the Willamette Valley and Puget Trough.
In March 2010, we established four treatment macroplots at Wild Iris Ridge and prepared them for management by removing existing vegetation using either shade cloth or herbicide application. Plots were then seeded in the fall of 2010 with an array native grasses and forbs.
In 2011 plots were randomly assigned one of three invasive species management treatments, or no treatment. The three treatments were hand weeding, grass-specific herbicide, or forb-specific herbicide application. Analysis of pre-treatment preparation and treatment effects was conducted after a final monitoring event in spring 2012.
Pre-treatment shade cloth reduced plant cover greater than herbicide, and the ratio of native to invasive species tended to be greater for shade cloth site prep than for those prepped with herbicide. Species tended to respond differently to management treatments following site preparation, though these responses were not found to be statistically significant. Application of both types of herbicide led to an increase in non-native species which were not killed by the selective herbicide. Thus, with use of a grass specific herbicide, managers might be substituting a problem with introduced grasses with one of introduced forbs. Likewise, use of a forb-specific herbicide resulted in higher cover of invasive grasses, across both site preparation types. Though hand weeding enabled us to target non-native species, our results suggest that treatments did not result in a statistically different plant community.
Future studies are recommended to observed the effects of pre-treatment site preparation on a larger scale. This management method may be able to provide land managers a “blank slate” for native seeding. Additionally, continued studies investigating other management techniques, such as carbon addition following site preparation, might enable us to increase understanding of treatments that might affect plant community composition.