Spatial Patterns of Trees in a Caribbean Semievergreen Forest

Spatial patterns of trees >10 cm dbh were studied in a 4—ha forest plot on St. John, United States Virgin Islands, by measuring nearest—neighbor distance for 28 tree species and mapping 5 uncommon species. Tree species diversity was high, with an even distribution of dominance (28 species out of 132 individuals, and H' = 4.37). A clumped distribution pattern with short intertree distances was prevalent. All but five species had average nearest neighbor distances of <25 m and most were <10 m. Indices of dispersion based on variance to mean rations for the 16 most abundant species suggested clumped distributions for 12 of the species, and only one regularly distributed species. Uncommon mapped species were located in distinct clumps of approximately 700—1300 m2, also with small average nearest—neighbor distances. The combination of high species diversity with many clumped distribution patterns and low interindividual distances for both common and uncommon species, suggests that mechanisms other than species—specific predators are important in understanding tree diversity differences between temperate and tropical forests. The importance of microhabitats is suggested. Available published evidences indicates a prevalence of clumped and a paucity of regular distribution patterns for tree species in tropical forests.