Floristic zonation, vegetation structure, and plant diversity patterns within a Caribbean mangrove and swamp forest on the bay island of Utila (Honduras).

摘要

Utila is a small island off the north coast of Honduras. More than two-thirds of its surface are covered by swamp forests and mangroves, since large areas of the topographically flat island are frequently inundated, favoring vegetation tolerant to the influence of brackish and/or salt water. These wetlands provide important ecosystem services and are the habitat of some endangered and well-studied narrow endemic reptiles. From a botanical point of view, however, the swamp forests of Utila have not received much scientific attention. Using quantitative data along a line-transect, we try to provide insight into the vegetation zonation and intrazonal structures, as well as into the diversity patterns and ecotonal complexity of the swamp forests on Utila. We found an apparent zonation pattern, but edges between units differ in terms of statistically significant distinctiveness and depth, resulting in either sharp boundaries between rather discrete communities or broad ecotonal transitions affecting whole sequences along the transect. While zonation is controlled by a factorial complex of physiochemical gradients, topography, and species competition, structural features seem to be related to large-scale disturbances. The variety of functional types, structural characteristics, and evenness patterns found in Utila's coastal forests far exceed species richness in terms of diversity.