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Reproductive success of tall boneset

Brett Bohlander, Debbie Jewell, Dan Zindrick, and Ryan Heffernan
Ecology class, BIO 342, Biology Department, DePauw University
Fall semester 2010

Tall boneset (Eupatorium altissimum) is a perennial wildflower in the family Asteraceae.  The plants grow up to 3 meters tall.  The plant produces conspicuous white flowers with flat tops. The plant tends to grow in sandy soils in open or recently disturbed areas.  In the quarry bottom of the Nature Park, we noticed that the plant is more common on rock mounds than on surrounding flat surfaces. 

We hypothesized that tall boneset would experience higher growth rates and higher reproductive success on rock mounds than on flat surfaces. 

We selected five mounds in the quarry bottom and set up 10 m transects, starting at the top of each mound and running downhill in a random direction.  At 1 m intervals along each transect, we recorded the number of plants, height of each plant, and number of flowers per plant.  We collected soil samples and measured soil moisture levels and soil texture. 

Plants were non-randomly distributed along each transect.  Higher proportions of plants were observed at the top of rock mounds with nearly uniform declines in numbers of plants as distance from the top of the mound increased.  Plants growing on top of rock mounds had longer roots, higher biomass, and higher numbers of flowers than plants growing farther away from rock mounds.  Soils were drier and were composed of more large rocks at the top of rock mounds. 

We conclude that tall boneset grows best in dry soils with rocky textures.  We are not sure why dry mounds provide more favorable growing conditions for tall boneset.  We recommend that future research on this plant be conducted to look at seasonal trends and soil pH.