This
scholarly article is a case study concerning the highly invasive common
buckthorn (Rhamnus Frangula) and its
current known impacts on forest anatomy in the northeast United States. The
common buckthorn is an invasive plant species that has been rapidly moving its
way through pine forests in the northeast USA for over 20 years now. The plant
is extremely shade tolerant and drought resistant, making it one of the most
likely plants to dominate a forest ecosystem. In the study, the survival and
growth of juvenile species of sugar maple, red maple, white ash and white pine
were monitored to determine if the shading caused by excess buckthorn was
causing the stunted growth or death of the seedlings. The ones performing the
study, M.E Fagan and D.R Peart of Dartmouth College, hypothesized that the
buckthorn would have the greatest negative effect on more shade intolerant
species due to the fact that the buckthorn reduces UV radiation reaching those
seedlings. By altering the production of seedlings due to buckthorn shading, it
was also hypothesized that the growth of seedlings into saplings would reduce
as well. This in turn causes less trees and diversity to grow full.
The study was performed on private
land of 2.5 hectares located in Signal Hill, New Hampshire for 9 years. More
than 75 percent of the mature trees were white pine with smaller densities of
the maple and ash seedlings. Buckthorn was seen to be at 100 percent coverage in
some spots. 30 random seedlings were chosen for measurement, all ranging in
shade tolerance gradient and each individual seedling was measured for annual
growth and extension and radial growth. The chosen seedlings were monitored and
observed as they did or did not morph into saplings.
After the study came to a
conclusion, the results were very vivid and clear. The first thing noted was
the saplings trying to grow under the buckthorn had lower mean extension growth
as well as lower radial growth. Although all the species differed in shade
tolerance, the decrease was still very similar across the board. Saplings
growing under just the pine canopy showed no significant effect on growth
change. It was also noted that most saplings that sprung growth under the
buckthorn showed stunted life spans by an average of 4 years. This showed the
studiers that it would take 22 years for a sapling to grow 1.3 meters in
height; very below the average growth rate for any of the seedlings.
The results of the study showed that
glosyy buckthorn has clearly reduced the growth of all seedlings and saplings
of the maple and ash species selected. It was proven that the saplings grew
much more rapidly in canopy openings away from the buckthorn where the limiting
resource, sunlight, was more prominent. Although the study was done with the
limiting resource as sunlight, the study claims that buckthorn is also rapidly
depleting nitrogen and minerals from the soil, decreasing pH, which in turn
causes diversity to slim and growth to slow. As a result, the professors drew
the conclusion that with the increasing dominance of the buckthrorn in pine
forests, changes in species diversity and composition rate of the forest are to
rapidly change as well. The buckthorn movement needs to be constantly monitored
in the pine forests of the northeast in order to plot the attack against it.
By: Matt Hollingsworth
Fagan, M.E, and D.R Peart. Impact of the Invasiveshrubglossybuckthorn (Rhamnus Frangula L.) on Juvenilerecruitment by Canopytrees. Dartmouth College, July-Aug. 2003. Web. <http://www.sciencedirect.com/science/article/pii/S0378112704001367>.
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