Demography and management of Willamette Daisy (Erigeron decumbens)
The goal of this project is to combine careful demographic studies with experimental habitat management treatments in order to provide information on effective management of the endangered Willamette daisy (Erigeron
The goal of this project is to combine careful demographic studies with experimental habitat management treatments in order to provide information on effective management of the endangered Willamette daisy (Erigeron decumbens ssp. decumbens). Specifically, we wish to assess the efficacy of various management techniques that will reduce the cover of invasive and woody plant species while maintaining or enhancing the cover of native species, including Willamette daisy.
We will test the effectiveness of mowing, prescribed fire + broad spectrum herbicide (glyphosate), glyphosate only, sheep grazing, grass-specific herbicide [Fusilade (Fluazifop)], and carbon addition as habitat management techniques in habitat occupied by Willamette daisy. We currently have little information on how Willamette daisy responds to these various management activities, however several of these management techniques have previously been found to be effective in enhancing cover of native prairies species in the Pacific Northwest. Treatments will occur within sites where Willamette daisy has be introduced. Conducting these experiments in natural populations of Willamette daisy would provide the best test of how Willamette daisy populations respond to management treatments. However, few populations are large enough to allow for a replicated study and agency regulations limit the scope of treatments that can be applied.
The Burn + Glyphosate treatment was the only treatment to have an effect on reproductive success of the Willamette Daisy. at Finely, Field 29, Burn + Glyphosate plots had significantly more flowers than the control plots.
Willamette daisy survivorship varied by site, however there were no significant treatment effects on the survivorship of Willamette daisy.The apparent lack of treatment effects on survival of Willamette daisy can be interpreted as an indication that though endangered, Willamette daisy can handle aggressive (but well-timed) management treatments without significant detrimental effects. Monitoring in 2014-2015 will track longer term treatment effects on the daisies that may not yet be evident.
Each treatment was also assessed for its overall effects on plant community. Listed below are each treatments effects on different plant species classes, both native and invasive.
- Mowing- Mowing did not have a significant effect on graminoid or forb cover (native or invasive) in either Recovery Zone. Shrub cover in the Eugene West Recovery Zone decreased with mowing.
- Grazing – Grazing by sheep in the Eugene West Recovery did not have a significant effect on graminoid or forb cover (native or invasive). Shrub cover decreased significantly in plots grazed by sheep.
- Grass-Specific Herbicide- The application of a grass specific herbicide decreased cover of invasive graminoid species in both Recovery Zones; native graminoid cover was not or increased. The application of grass- specific herbicide increased shrub cover in the Eugene West Recovery Zone.
- Burning + Glyphosate- The application of a broad-spectrum herbicide after the first flush of green-up post-burn decreased cover of invasive grasses and invasive forbs in the Corvallis West Recovery Zone; native graminoids and forbs were not affected. Burning occurred in the Fall of 2012 at Eugene West sites, and decreased invasive graminoids (but increased invasive forbs).
- Glyphosate – The application of glyphosate in the fall had no significant effect on the cover of native or invasive species.
- Carbon Addition- As of 2013, carbon addition had no significant effect on the cover of native or invasive forb species, however carbon addition did tend to decrease cover of native graminoids in the Corvallis West Recovery Zone.
The activities reported here are part of a 3-phase, 6-year project. In Phases 1 and 2, we have introduced populations of Willamette daisy, implemented 2 years of habitat treatments, and monitored the effects on Willamette daisy and surrounding vegetation. We are currently, in the process of completing Phase 3 which will include treatments and monitoring of plots outplanted in 2011 and 2013, as well as analysis of all data collected over the course of the study. We plan to use the information gained from all phases to inform management at both introduced and natural populations of Willamette daisy.