PHENOLOGY IN FUNCTIONAL GROUPS OF CENTRAL AFRICAN RAINFOREST TREES

A good understanding of the phenology of rainforest trees would help in anticipating ecosystem response to future global climate change. Extensive and long-term phenological observations in the tropics are rare and difficult to realise but unpublished historical records have been preserved and are of high value. Phenological data gathered between 1948 and 1957 on 3642 trees of 158 species in the rainforest reserve of Luki, Democratic Republic of Congo were analysed. Patterns of leaf shedding, flowering, fruiting and fruit dispersal were presented for three major functional groups of trees and their relationships with rainfall investigated. Annual rhythms of leaf and reproductive phenology were observed with patterns ranging from synchronous annual peaks to continuity. Over the years, positive association was found between leaf shedding and annual rainfall for shade-tolerant canopy species as well as between reproductive phenology and annual rainfall for long-lived heliophilous and shade-tolerant understorey species. Direct and indirect associations with intra-annual and supra-annual climate variations suggest that changes in environmental conditions may affect phenological patterns of tropical trees thus species interactions and ecosystem dynamics. The different leaf and reproductive phenological patterns found in different functional groups of trees promote the coexistence of numerous tree species in tropical rainforest multispecies communities. The associations between tree phenology and rainfall also reinforce the evidence for potential effects of climate variations on the ecology of Central African forests.