Nutrient cycling and biomass characteristics of a tropical palm forest dominated by Orbignya cohune were found to be different from those of hardwood dominated forests. The cohune palm forest had a high proportion of biomass in leaves (5 per cent), a reduced sapling layer, a large amount of standing forest litter and an exceptionally low decomposition rate factor (0.1 year-1). Mineral concentrarions in palm leaves were generally lower than in hardwood species with the exception of Na, which was exceptionally high in Orbignya cohune. Biomass was estimated at 226 tons ha-1 containing 1173 kg ha-1 N; 126 kg ha-1 P; 437 kg ha-1 K; 1869 kg ha-1 Mg; 125 kg ha-1 Ca, and 2177 kg ha-1 Na. Soils of cohune association did not differ significantly from those of neighbouring hardwood dominated associations with the exception of Na which occurred in higher concentration because of bioaccumulation in the dominant. The results suggest that the growth habits and physiology of a dominant can strongly influence some of the ecological parameters used to describe a forest association