When catastrophic windstorms remove forest canopy, the forest floor is disrupted by the uprooting of trees, leaving mounds, pits, and other microsites. These microsites are important for regeneration of many tree species. The objective of this suite of studies is to describe the different microsite environments and examine the physiological and demographic mechanisms by which trees respond to these environments. An integrative approach, combining descriptive community-level studies with experimental studies of individuals and populations will be used. This research is being conducted on the Harvard Forest Long-Term Ecological Research Sites, where hurricane blowdowns have been simulated by pulling down canopy trees. Five canopy tree species: red maple, red oak, black birch, white birch, and yellow birch will be studied. The central hypothesis is that forest regeneration can be explained in terms of species-specific responses to light, temperature, water, nitrogen, and carbon dioxide. Fluxes of these factors in the forest understory and on five microsites created by simulated hurricane blowdown will be examined. Patterns of environmental factors will be related to seed and seedling demography and to growth and physiology of individual seedlings. Changes in the understory community following disturbance will also be monitored to detect effects of understory vegetation on the forest floor environment and on tree regeneration.
