Tree Phenology in a Tropical Montane Forest in Rwanda

Abstract

The phenology of 568 trees of 49 species producing fleshy fruits was studied in a montane forest in Rwanda between January 1991 and January 1993. Fruiting peaked during the major wet season in March-May, but remained high during the major dry season in July-August. A period of reduced fruiting occurred in the beginning of each calendar year during the minor dry period. Leaf flushing peaked during the major dry season in July-August, whereas flowering peaked in the beginning of each calendar year. These observations were inconsistent with the general pattern predicted by an insolation-limitation hypothesis that community-wide flowering and leaf flushing in tropical forests should be closely related in time and that both phenophases reach their peaks during the period of the most intense insolation. When species were grouped by seed size, the large-seeded group displayed a greater temporal variation in fruit abundance (greater fruiting seasonality) than the small-seeded group. When species were examined individually, however, seed size was not related to either fruiting duration or within-species fruiting synchrony, two attributes determining the degree of fruiting seasonality of a species. Fruiting patterns manifested by a group thus could not be explained by attributes from species constituting the group. Different degrees of fruiting seasonality displayed by different seed-sized groups may be due to different degrees of within-group interspecific fruiting synchrony.