Floristic composition and diversity of mixed primary and secondary forestsin northwest Guyana

The adequate protection and sustainable management of a tropical rain fores t requires a good knowledge of its biodiversity. Although considerable part s of Guyana's North-West District have been allocated as logging concession s, little has been published on the forest types present in this region. Th e present paper reviews the floristic composition, vegetation structure, an d diversity of well-drained mixed and secondary forests in northwest Guyana . Trees, shrubs, lianas, herbs and hemi-epiphytes were inventoried in four hectare plots: two in primary forests, one in a 20-year-old secondary fores t and one in a 60-year-old secondary forest. The primary forests largely co rresponded with the Eschweilera-Licania association described by Fanshawe, although there were substantial variations in the floristic composition and densities of dominant species. The late-succession forest contained the hi ghest number species and was not yet dominated by Lecythidaceae and Chrysob alanaceae. There is a need for updating the existing vegetation maps of nor thwest Guyana, as they were based on limited information. Large-scale fores t inventories may provide a fair indication of species dominance and forest composition, but do not give a reliable insight in floristic diversity. Al though previous reports predicted a general low diversity for the North-Wes t District, the forests plots of this research were among the most diverse studied in Guyana so far. These results will hopefully influence the planni ng of protected areas in Guyana.