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A long-term evaluation of fruiting phenology: importance of climate change
- Colin A. Chapman, Lauren J. Chapman, Thomas T. Struhsaker, Amy E. Zanne, Connie J. Clark, John R. Poulsen
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- Journal:
- Journal of Tropical Ecology / Volume 21 / Issue 1 / January 2005
- Published online by Cambridge University Press:
- 10 January 2005, pp. 31-45
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Within the last decade the study of phenology has taken on new importance because of its contribution to climate-change research. However, phenology data sets spanning many years are rare in the tropics, making it difficult to evaluate possible responses of tropical communities to climate change. Here we use two data sets (1970–1983 and 1990–2002) to describe the fruiting patterns of the tropical tree community in Kibale National Park, Uganda. To address variation in spatial patterns, we describe fruiting over 2–3 y among four sites each separated by 12–15 km. Presently, the Kibale region is receiving c. 300 mm more rain than it did at the start of the century, droughts are less frequent, the onset of the rainy season is earlier, and the average maximum monthly temperature is 3.5 °C hotter than it was 25 y ago. The 1990–2002 phenology data illustrated high temporal variability in the proportion of the populations fruiting. Interannual variation in community-wide fruit availability was also high; however, the proportion of trees that fruited has increased over the past 12+y. At the species level a variety of patterns were exhibited; however, a number of the most common species currently rarely fruit, and when they do, typically <4% of the individuals take part in fruiting events. Combining the data set from 1990 to 2002 with that from 1970 to 1983 for specific species again reveals an increase in the proportion of trees fruiting between 1990 and 2002; however, the proportion of the populations fruiting decreased during the earlier period. When one examines particular species over this whole period a variety of patterns are evident. For example, Pouteria altissima exhibited a relatively regular pattern of fruiting during the 1970s; however, it rarely fruited in the 1990s. Contrasting phenological patterns at four sites revealed that at the community level the fruiting patterns of only one of the six pair-wise site combinations were correlated. Relationships between rainfall and fruiting were variable among sites. Contrasting changes in fruiting patterns over the 30 y with differences among the four sites varying in rainfall, suggests that the changes observed in fruiting may be due to climate change. Responses to this climate change are likely complex and will vary among species. However, for some species, current conditions appear unsuitable for fruiting.
Fruit and flower phenology at two sites in Kibale National Park, Uganda
- C. A. Chapman, R. W. Wrangham, L. J. Chapman, D. K. Kennard, A. E. Zanne
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- Journal:
- Journal of Tropical Ecology / Volume 15 / Issue 2 / March 1999
- Published online by Cambridge University Press:
- 01 March 1999, pp. 189-211
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Examination of phenological patterns of tropical trees at different temporal and spatial scales can elucidate biotic and abiotic factors that correlate with fruiting, flowering and/or leaf set patterns. In this study, 3793 trees from 104 species in Kibale National Park, Uganda were monitored. The trees were selected from two sites (Kanyawara and Ngogo) separated by 10 km. Trees were monitored monthly to document community-wide and population-level fruiting and flowering patterns for a maximum of 76 mo. Analysis of two sites over a number of years permitted examination of generalities of patterns found on smaller spatial and temporal scales. Spectral analysis indicated that community-level flowering and fruiting at Kanyawara exhibited regular annual peaks, although the flowering peaks were of shorter duration. At Ngogo, community-level flowering also displayed regular annual peaks, but fruiting had an irregular pattern with no distinct peaks. The abundance of fruiting 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 beginning, this suggests that the minimum temperature in the previous dry season is important in determining how many individuals fruit. Flowering at Kanyawara peaked immediately after the maximum annual period of high irradiance. Within-species synchronization was evident in the flowering for all species examined at Ngogo and for 64% of those at Kanyawara. Fruiting was synchronous 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 Kanyawara and Ngogo. For some species, trends that were suggested from one year of data were not supported when additional years were considered. Although these two sites are close together, share many of the same species, and experience similar climatic regimes, many phenological patterns were site-dependent.