The Adirondack Mountains of New York State hold the southernmost communities of alpine vegetation in the eastern United States.  Containing the greatest concentration of rare and endangered species found in New York State, this ~12,000-year-old ecosystem is important in the ecological history of northeastern North America and in its biodiversity.  Unfortunately, this alpine ecosystem is increasingly subject to anthropogenic disturbance from hiker traffic and atmospheric pollutants.  In order to obtain a better understanding of species diversity and to document changes in vegetation composition, a 300 ft permanent transect was established on the summit of Mt. Marcy in 1957.  In 1984, an additional 11 permanent transects, each 30 m long, were established in the McIntyre range on the summits of Algonquin, Wright, Boundary, and Iroquois. In addition to assessing species diversity and vegetation change, these transects were established to evaluate the degree of vegetation re-colonization on sites freed of hiker impact.  Based on data collected from the Marcy transect in 1957 and 1981, I predicted that current sampling data would show that while there may be little overall change in vegetation, there would be measurable changes in species composition.  Using the point-intercept method, the 11 McIntyre transects were sampled in 1984 and 1994.  Species occurring every 5 cm along each 30 m transect provided 600 data points for each transect. I re-sampled these same transects in 2002 and 2007.  I then compiled and compared all data collected between 1984 and 2007 in order to analyze vegetation change over this 23-year period.

Results/Conclusions

Results revealed that vegetation composition changed significantly, with an overall decrease in bryophytes/lichen and an increase in vascular plants, indicating that a successional change involving vascular plants replacing bryophytes is occurring in areas lacking anthropogenic disturbance.  While these results show that vegetation re-colonization and succession is occurring in areas freed of hiker traffic, results may also indicate expansion of sub-alpine forest vegetation, in line with predictions about the effects of global warming on alpine plant communities.