Multiple and interacting disturbances lead to Fagus grandifolia dominance in coastal New England

BUSBY, P. E., G. MOTZKIN, AND D. R. FOSTER (Harvard Forest, Harvard University, Petersham, MA 01366). Multiple and interacting disturbances lead to Fagus grandifolia dominance in coastal New England. J. Torrey Bot. Soc. 135: 000–000. 2008.—Recent studies have emphasized the importance of multiple and interacting disturbances in controlling plant community dynamics. However, detailed information on disturbance history and changes in species abundance are unavailable for many forest ecosystems. As a result, it is often difficult to evaluate the influence of disturbance interactions on changes in species composition over time. This study examines the history and dynamics of Fagus grandifolia-dominated forests in coastal New England to evaluate the role of multiple disturbances in the development of Fagus dominance. Detailed historical and dendroecological data were used to reconstruct disturbance history and compositional trends for the past . 300 years. At the time of European settlement, the study area supported mixed forests of Quercus, Fagus, Carya, and Pinus. Intensive harvesting in the early 19 century resulted in abundant Quercus alba, Q. velutina, and Fagus regeneration. Thereafter, harvesting and fire were limited, but repeated low-moderate intensity hurricanes allowed Fagus but not Quercus species to establish and persist in the forest understory. A severe hurricane in 1944, accompanied by intense herbivory from a high deer population, accelerated the development of Fagus dominance by releasing Fagus saplings, initiating Fagus establishment, and preventing Quercus establishment. The extreme shade tolerance of Fagus, in combination with its flexible regeneration strategy (i.e., the ability to regenerate from seed or from root sprouts), and low palatability to deer, contributed to the increase in abundance of Fagus in response to this complex disturbance history. Thus, long-term changes in forest composition and reduced species richness resulted from species-specific responses to multiple, interacting disturbances.