Distribution and Ecology of the Fungal
Pathogen of Dicranum fulvum
Edna Bailey Sussman Foundation
Brittany Cronk
December 2008
Summary of Proposed Work:
Mosses, while small in stature, play a large role in forested ecosystems by
providing habitat for other organisms and facilitating forest nutrient cycling. Mosses are
generally thought to be disease resistant, but four years ago, an outbreak of an unknown
pathogen began causing dieback in mosses at Cranberry Lake Biological station. The
disease symptoms were observed in the moss Dicranum fulvum on the glacial erratics
within the mixed hardwood forest. The boulders are a unique feature of the forest and
support a diverse community of bryophytes, ferns, wildflowers as well as associated
microbes and invertebrates.
The symptoms include circular areas of dieback, a blackened plaster like
appearance and a decrease in the overall height of the moss. The disease spread rapidly
into other nearby boulder fields. It created large areas of moribund moss that was once a
healthy green carpet. This moss is one of the most prevalent boulder top mosses in the
hardwood forests of the Adirondacks. Destruction of this microhabitat could cause
devastating effects on the ecology of microorganisms. The goal of my research is not
only to identify the causal agent, but also to study the environmental variables involved
and to learn about the spread of this devastating disease throughout the Adirondack park.
My proposed work was to further investigate the growth rate of the disease, the
interaction between the species as well as what environmental variables affect the spread
in the field. This past summer I did studies on the disease of this moss throughout the
Adirondack Park. The Wild Center, Natural History Museum of the Adirondacks had
agreed to sponsor my project. My proposed work for this internship was to create a
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brochure that could be distributed to the public about the mosses that could be seen at the
Wild Center.
Narrative of Actual Work:
I first began my fieldwork by creating a post card that I could leave at trail heads
and gas stations that included a photograph, description of the moss disease and details
on how the public could contact me if they happened upon the disease in their travels.
Since I was just planning on searching for the moss, I figured this would be a good place
to begin. Below is a photograph of the disease of Dicranum fulvum.
Figure 1: Photograph of
fungal disease of Dicranum
fulvum. Photo taken at
Cranberry Lake Biological
Station , Sucker Brooke
Trail, Summer 2007.
I then traveled through the majority of the main roads throughout the Adirondack park,
stopping at trail heads. My methods at each trailhead were as follows:
- Hiked about 0.5-1 mile.
- Looked for boulders that contained Dicranum fulvum.
- Searched for disease within the moss carpets.
- If I had found boulders that contained D. fulvum, I would create three
quadrats along a line that was 50 meters. The quadrats had the radius of
1.78 meters. I would walk in a circle, which had the area of 10 m2 and
measure all of the trees that fell within that area that were over 10 cm (4
in) diameter at breast height. This was performed at the 0 m, 25 m, and
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50 m marking along the 50 m line. This allowed me to get an idea of the
forest’s tree composition. I had hypothesized that forest canopy not only
affected the presence of D. fulvum growth on boulders, but that it could
also affect the presence of the disease.
- If there were symptoms or signs of disease I would sample all of the
boulders along the 50 m line that fell within one meter of each side of
the line. This gave a total sampling area of 100 m2. On each of the
boulders I would perform point intersect transects on the boulders them
selves. This involved using measuring tape to set up an X on the boulder
and take notes one what moss was present at each 10 cm marking along
the tape. This could give an idea what percentage of disease there was
on the boulder as well as what other mosses and lichens were present.
- At each site that I found D. fulvum (dead or healthy) I collected large
samples of moss, originally planned for a nitrogen analysis. There have
been studies that nitrogen can influence the virulence of a pathogen.
Because mosses typically live in areas that are low in essential nutrients,
an excess of nitrogen can stress the moss and make it more susceptible
to infection. Also in the mixed hard wood forests for the summers of
2005 and 2006 there was a heavy Forest Tent Caterpillar outbreak that
could have increased the amount of nitrogen (in the form of frass) on
these boulders within these forests.
I have not currently analyzed all of the data resulting from these studies but I had
found disease of D. fulvum throughout the entire Adirondack Park. It seemed that had
been spreading fast and the infections that I had observed were new. Boulders that were
isolated in the forest, away from any nearby boulder field had also been infected. The
disease did not seem to be impacted only in dense boulder fields close to nearby
inoculum sites.
I also recorded data on my existing sites that I had observed two years previously.
This involved photographing existing disease rings on boulders to record growth rate
changes. I am analyzing the photographs by using the program ImageJ. Images of a
established control were also photographs. The controls were created in areas on the
boulders that did not contain any disease symptoms. Throughout the three years many of
the controls have developed symptoms of the disease. Observations were also collected
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for a transition matrix. This allows us to understand how the disease is affecting the
ecology of the boulder tops. The transition matrix provides and idea on how the existing
conditions will change from one year to the next.
I am calling this fungal pathogen unknown because it is still in debate of what it
is. I had originally thought that it was a cup shaped ascomycete within the genus of
Bryoscyphus. I had isolated what I thought was this fungus in culture from the fruiting
bodies found on the moss. I had done a small practice test where I inoculated moss to see
if this fungus had produced any signs and symptoms against a control. This fungus had
produce symptoms very quickly in the containers that had the highest concentration of
inoculum. The control did not change. Then I isolated the DNA of this fungus and had it
analyzed. I did a blast search within GenBank and it came back with 99% accuracy of
being within the genus Fusarium. This all has to be repeated with a higher standard of
accuracy before any results can be completely determined.
For my internship I made a brochure on the mosses that can be found along the
nature trail of the Wild Center. The public could use this brochure to learn more about
different kinds of mosses and a bit about their ecology and roles in the ecosystem. The
brochure can be found in a separate attachment. I also gave a powerpoint presentation on
the ecology of mosses to a crowed of about 35 people. The lecture lasted about 1 hour,
and then we regrouped and went on a moss walk where I distributed the brochure so that
everyone could follow along. Within the group I had a mix of people with varying levels
of background knowledge in ecology. Below are a few photographs of the moss walk.
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Figure 2: Observing the differences in
characteristics of Polytrichum and
Pleurozium. Director of Programs for the
Wild Center, Jen Kretzer is in green.
Figure 3: Describing how to observe the
detail of the intricate architecture of moss
using a hand lens.
Discussion of Future Work:
This internship allowed me to finish up all the field work necessary for my
masters thesis research. In the near future I plan on analyzing the data using statitistcal
anlaysis software. I plan on using the large collections of moss to re-isolate the fungal
pathogen as well as using moss spores to grow D. fulvum in sterile culture. Then I can reinoculate the moss and with a more accurate and precise method, I could really prove
pathogenicity. I will also perform another round of DNA analysis and identify the fungus.
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Identification, proof of pathogenicity and an understanding of the ecology of the disease
would all be included in my masters thesis. Any published works that come from this
research will acknowledge the Edna Bailey Sussman Foundation for their outstanding
contribution to my research. Thank you for giving me this opportunity.
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