• Maya Mountains;
  • permanent plot inventory;
  • tree diversity;
  • tropical rainforest

Most of the undisturbed forests of northern Central America remain undescribed. Some studies predict that tree species richness in lowland forests of northern Central America should be much lower than in similar forest types in southern Central America. This paper describes the physical and biological structure of two permanent, one-hectare plots on a valley floor in the Bladen Nature Reserve, Belize and compares these plots with other forests in the Neotropics. The plots have 91 and 89 species of trees ≥ 10 cm diameter (327 and 358 individuals, respectively) and comparable or higher measures of alpha-diversity than other such forests in Central America. The recorded tree species richness from other forests in northern Central America may be lower than those in southern Belize. The plots are dominated by Mortoniella pittieri Woodson (Apocynaceae), a disjunct from Costa Rica and Nicaragua. More than 50% of the tree species have distributions ranging into Bolivia or Peru, and >75% are wide-ranging species. The plots have a lower tree density and a higher proportion of large trees (>70 cm dbh) than other wet Neotropical forests. Like other Neotropical forests, tree species in the plots are generally aggregated and have a high proportion of vertebrate-dispersed fruits. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 138, 275–296.