A palynological record of a secondary succession after fire in the Gran Sabana, Venezuela

Abstract

Fire has been considered one of the most important factors in the expansion of savannas in the Gran Sabana region. In Urué, an important fire event that occurred before 1.6 kyr BP led to the replacement of ‘primary’ forests by savannas and morichales (monospecific communities of the palm Mauritia). In the present work, the secondary succession after fire is reconstructed by palynological analysis of a previously dated clay core, and the results are compared with those from studies based on present-day ecosystems. Charcoal analysis is used to infer fire incidence and surface samples are used as modern analogues. The secondary succession is subdivided into seven seral stages: open secondary forests, helechal or dense fern community, transitional savanna, wet savanna with morichales, treeless savanna, wet savanna with morichales, and treeless savanna. Fires were common at the beginning, but climate constituted the main successional control from the transitional savanna stage onwards. The process is characterised by a continuous impoverishment of taxa, but there was a steady increase in Mauritia, due to its ability to colonise new habitats created by disturbances. The conclusions of this palynological reconstruction show good correspondence with present-day studies on fire ecology. Copyright © 1999 John Wiley & Sons, Ltd.