Demography and Management of Willamette Daisy (Erigeron decumbens)

In 2011 and 2013 Institute for Applied Ecology outplanted at total of eight populations (4 in 2011 and 4 in 2013). In each year, two plots were outplanted in both the Eugene and Corvallis West Recovery Zones. Survivorship was measured for each population and plots then received a variety of management treatments to evaluate the response of both the daisy and the surrounding plant community to management treatments. Measurements of plant vigor, as well as the plant community were taken annually, and are reported here.
Willamette Daisy Response to Treatment:
Results indicate that treatments for plants outplanted in 2011 had no signifincant effect on survivorship; indicating that well timed (and even aggressive) management treatments may be an effective tool for managing Willamette daisy. There were however, significant effects on plant size, reproduction and recruitment which indicate that Burn + Glyphosate increased both plant size and reproductive effort. Additionally the highest number of recruits were found in the Burn + Glyphosate plots at Field 29, (Finley, Corvallis West Recovery Zone. )
In 2014, 25 of the 75 plants originally outplanted in the Burn + Glyphosate plots at Field 29, had produced recruits, and the number of recruits at this site (289) is as high (or greater) than the number of plants surviving in introductions included as a part of this study. Recruits were also noted in the Glyphosate only plots as well as in the mowed plots at Kirk East.
Plant Community Response to Treatment:
Despite the apparent lack of effect on Willamette daisy survivorship, the effects of management treatments on the plant community varied by site. While the response of plant community varied by site (and starting condition), the most successful treatments for decreasing invasive forb, invasive graminoid and woody/shrubby species cover was the Burn + Glyphosate treatment (followed by mowing, glyphosate only and carbon addition).
Plots that were dominated by invasive forbs (dominantly Hypochaeris) responded positively to carbon addition with significant decreases in invasive forb (and less so invasive graminoid) cover following treatment. This response was similar to that observed in the glyphosate only plots, where treatments also decreased cover of invasive forbs.