Journal of Tropical Ecology

An analysis of the floristic composition and diversity of Amazonian forests including those of the Guiana Shield

a1 Department of Plant Ecology, Utrecht University, PO Box 80084, 3504 TB Utrecht, The Netherlands (
a2 The Tropenbos Guyana Programme, 12E Garnett Street, Campbellville, Georgetown, Guyana
a3 ORSTOM, Laboratoire Botanique, 163 Rue A. Broussonet, 34000 Montpellier, France
a4 Universidad Nacional Experimental de Guayana, Calle Chile, Urbaniz Chilemex, Puerto Ordaz, Edo. Bolívar, Venezuela
a5 Hugo de Vries laboratory, University of Amsterdam, Kruislaan 318, 1098 SM Amsterdam, The Netherlands
a6 Universidade Paulista, Lab. Botânica, Av. Paulista 900 1° andar., São Paulo-SP, 01310-100, Brazil
a7 National Agricultural Research Institute, Mon Repos, ECD, Guyana
a8 Institute of Systematic Botany, The New York Botanical Garden, Bronx, New York 10458-5126 USA


A large number of newly published and unpublished hectare plots in Amazonia and the Guiana Shield area allow an analysis of family composition and testing of hypotheses concerning alpha-diversity in the south American rain forest. Using data from 94 plots the family-level floristic patterns in wet tropical South America are described. To test diversity patterns, 268 plots are used in this large area. Contrary to a widely held belief, western Amazonian plots are not necessarily the most diverse. Several central Amazonian plots have equal or even higher tree diversity. Annual rainfall is not a good estimator for tree diversity in the Amazonia area and Guiana shield. Plots in the Guiana Shield area (and eastern Amazonia) usually have lower diversity than those in central or western Amazonia. It is argued that this is not because of low rainfall or low nutrient status of the soil but because of the small area of the relatively isolated rain forest area in eastern Amazonia and the Guiana Shield. The low diversity on nutrient-poor white sand soils in the Amazon basin is not necessarily due to their low nutrient status but is, at least partly, caused by their small extent and fragmented nature.

(Accepted April 9 2000)

Key Words: Amazonia; floristic composition; Guiana Shield; rainfall; tree alpha diversity.