Tree Species Diversity in the Eastern Deciduous Forest with Particular Reference to North Central Florida

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Abstract
Tree species diversity in forests from north central Florida is partially a function of the successional status of the community, the portion of the environment occupied and the ecological amplitude of the species. Diversity is higher in climax communities where greater uniformity exists between tree, sapling, and seedling size classes. Mesic fertile sites support communities with higher diversities than wet or dry sterile sites. Successional species tend to have wide ecological amplitudes. They generally occupy extreme environments or areas under disturbance. They are not competitive in mixed populations, and as a consequence they are more successful in assembled populations with low diversities. As successional species ameliorate extreme environments followed by, the arrest of controlling variables such as fire, climax pioneer species may invade successional communities thereby increasing diversity. With continued arrest of controlling variables, successional features are lost. The climax pioneer group possess wide ecological amplitudes and are sufficiently competitive in mixed populations to permit their incorporation into the climax community. It is this group that lends floristic continuity to the climax. A 3rd group, the climax exclusives, invades the community following the acquisition of climax characteristics. The climax exclusives are adapted to specific environmental situations and, consequently, have narrow ecological amplitudes. The noted increase in diversity from successional to climax communities is related in part to the progressive addition of the climax pioneers and climax exclusives while maintaining a few successionals in the population. Diversity within the eastern deciduous forest exhibits 2 general trends: decrease with distance from the mixed mesophytic association and decrease with arid and colder climates. The former lends strong support to Dr. Braun''s contention that the mixed mesophytic association served as the ancestral form from which other members of the eastern deciduous forest arose in whole or in part.