Fruit and flower phenology at two sites in Kibale National Park, Uganda

Examination of phenological patterns of tropical trees at different tempora l and spatial scales can elucidate biotic and abiotic factors that correlat e with fruiting, flowering and/or leaf set patterns. In this study, 3793 tr ees from 104 species in Kibale National Park, Uganda were monitored. The tr ees were selected from two sites (Kanyawara and Ngogo) separated by 10 km. Trees were monitored monthly to document community-wide and population-leve l fruiting and flowering patterns for a maximum of 76 mo. Analysis of two s ites over a number of years permitted examination of generalities of patter ns found on smaller spatial and temporal scales. Spectral analysis indicate d that community-level flowering and fruiting at Kanyawara exhibited regula r annual peaks, although the flowering peaks were of shorter duration. At N gogo, community-level flowering also displayed regular annual peaks, but fr uiting had an irregular pattern with no distinct peaks. The abundance of fr uiting trees at Kanyawara was negatively related to the minimum temperature in the previous season (3-7 mo prior). Since fruiting tended to peak when the first wet season of the year was ending and the dry season was beginnin g, this suggests that the minimum temperature in the previous dry season is important in determining how many individuals fruit. Flowering at Kanyawar a peaked immediately after the maximum annual period of high irradiance. Wi thin-species synchronization was evident in the flowering for all species e xamined at Ngogo and for 64% of those at Kanyawara. Fruiting was synchronou s within species for 64% of the species at both sites. Despite this general community-level synchronization, the months of peak fruiting and flowering for some species varied markedly among years. Furthermore, for a number of species the timing of fruiting or flowering events differed between Kanyaw ara and Ngogo. For some species, trends that were suggested from one year o f data were not supported when additional years were considered. Although t hese two sites are close together, share many of the same species, and expe rience similar climatic regimes, many phenological patterns were site-depen dent.