Extirpating an Exotic Invasive from the Ecosystem Preserve

1
Extirpating an Exotic Invasive from the Ecosystem
Preserve

• Experimental Removal of Buckthorn by students in
  Biology 243 (Plant Biology)
• Poster prepared by Adam Derrickson, Alan Kalf,
  and
• Dr. David Warners

2
Exotic Invasive Species

• 22 of plant species in North America today are
  non-native, having originated on a different
  continent.
• 400 of these non-native species are considered
  invasive because they pose serious threats to
  native habitats.
• This biological pollution has already reduced
  the populations of 42 of our nations endangered
  plants.
• In 1998 an inventory of Calvins natural area
  turned up 307 plant species, 100 of which are
  non-native.
• The most threatening non-native plants at Calvin
  are garlic mustard (Alliaria petiolata), purple
  loosestrife (Lythrum salicaria), and two species
  of buckthorn (Rhamnus cathartica and R. frangula).

3
Buckthorn (Rhamnus cathartica and R. frangula)

• Buckthorn is native to Eurasia and first arrived
  in North America in the late 1800s.
• Its rapid growth and wide tolerance range make it
  highly valued by landscapers and homeowners.
• Both species of buckthorn are sold as ornamental
  shrubs in Grand Rapids and throughout Michigan..
• Buckthorn is rapidly spread by birds (starlings,
  robins, waxwings) who eat the fruit and disperse
  the seeds in their feces.
• In natural areas, buckthorn outcompetes and
  replaces native vegetation.

4
Experimental Design

• Four removal treatments were performed digging,
  cutting, cutting and applying herbicide, and
  injecting with herbicide.
• Each treatment was repeated by 4 groups (16
  groups total) during the week of September 20-24,
  1999.
• Each group (of 4-6 students) worked for one hour
  and recorded the number and diameter of every
  buckthorn they treated.
• Data were pooled and summarized to compare the
  efficiency of the different treatments.
• Next years class will evaluate the regrowth from
  treated shrubs and assess long-term effectiveness
  of each treatment

5
Four Treatments

• Digging - shovels were used to remove entire
  shrubs flags indicate where shrubs had been
• Cutting - loppers were used to cut shrubs
  approximately 10 cm above soil surface cut
  shrubs were removed.

6

• Cutting and Painting - shrubs were cut and
  Round-up herbicide was painted on the exposed
  stumps cut shrubs were removed.
• Injecting - an E-Z-Ject herbicide injector was
  used to shoot small shells of herbicide into
  the base of shrubs.

7
Results and Conclusions

• 615 shrubs were treated by 80 students in three
  days.
• The number of shrubs treated showed little
  variation between treatments, partially due to
  high variation among the groups who were
  performing the same treatment.
• The injection treatment appears to have treated
  the largest buckthorns, possibly because workers
  in the other treatments avoided the largest
  shrubs.
• Digging was the most disruptive treatment to the
  soil and nearby plants, and the least efficient,
  although long term success with digging is
  expected to be high.

8
Management Suggestions

• It will be important to monitor the test plots
  from this study to evaluate the regrowth success
  of the various treatments. After next years
  class evaluates regrowth, management guidelines
  can be developed.
• Based upon this years data, many students
  recommend a combination of the injection
  treatment for large buckthorns and either a cut
  and paint or digging treatment for the smaller
  buckthorns.
• 80 students each working one hour made a dent in
  the buckthorn population of the Ecosystem
  Preserve, but only a very small dent. More
  removal projects are needed. Buckthorn is
  everywhere!