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Non-arborescent vegetation trajectories following repeated hurricane disturbance: ephemeral versus enduring responses

Royo,A.A., Heartsill Scalley, T., Moya, S., Scatena, F.N.
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Hurricanes strongly influence short-term patterns of plant community structure, composition, and abundance and are a major contributor to the maintenance of plant diversity in many forests. Although much research has focused on the immediate and long-term effects of hurricane disturbance on tree diversity, far less attention has been devoted to the non-arborescent understory community that often account for the vast majority of the vascular species. Using a unique 20 year dataset, we tracked changes in richness, cover, biomass, and diversity (H') of non-arborescent species following Hurricane Hugo (1989) and Hurricane Georges (1998) in a mature secondary subtropical wet forest of Puerto Rico. Hurricanes caused an immediate, albeit transient, increase in overall species richness, cover, and diversity. Over a twenty year period, the non-arborescent community exhibited pronounced and persistent changes in composition, including a dramatic increase in abundance and richness of ferns and vines and a concomitant decrease in forbs and shrubs. By 2010, understory composition and relative abundance hierarchies were significantly altered; ferns and vines combined comprised 75 and 90% of total understory cover and biomass, respectively. Our results for this community contrast sharply with prior studies on similar temporal and spatial scales that demonstrate hurricanes rarely alter dominant tree species composition over the long-term. These results suggest that the role of hurricane disturbance in structuring plant diversity may be even more important than previously thought.

Department of Earth and Environmental Science / University of Pennsylvania, 251 Hayden Hall, 240 South 33rd Street, Philadelphia, PA 19104-6316