The structure and diversity of rain forests at Bajo Calima, Choco Region, western Colombia

The rain forests at Bajo Calima, Colombia are described for woody plant composition. Two upland plots, 1.0 and 0.5 ha in size, were selected and all trees $\geq$ 10 cm dbh were measured and identified. Trees $\geq$ 2.5 cm and $\leq$ 9.9 cm dbh were sampled in 0.1 ha subplots. Biomass was estimated using allometric equations. Biomass levels are low, at 210 tons/ha, and tree canopy heights rarely exceed 30-35 m. Few trees over 100 cm dbh were found. Forests at Bajo Calima are among the most species-rich in the world, with over 250 tree species $\geq$ 10 cm dbh per ha. Palms are numerically abundant in the overstory, with Jessenia bataua being most common. Free-climbing lianas are uncommon. Only 11 species had more than 8 individuals $\geq$ 10 cm dbh per ha. Measures of soil nutrients indicate low fertility and possible aluminum toxicity The pluvial rain forests at Bajo Calima lend support to previous findings that high diversity is correlated with both high rainfall and low nutrient levels.