Phenology of floodplain forest trees in the Peruvian Amazon : choreographed by annual flooding ?

Speaker: Ruksan Bose (French Institute of Pondicherry (Previously master's degree student at : AgroParisTech-ENGREF, Montpellier)

Organiser : Department of Ecology, French Institute of Pondicherry.

Venue : Jawaharlal Nehru Conference Hall, French Institute of Pondicherry, 11, Saint Louis Street, Pondicherry - 605 001.

Abstract

Patterns of reproductive and vegetative phenology have been characterized for 13 commercially valuable floodplain forest tree species in the Peruvian Amazon. Apart from describing less-known phenomena and the interaction with environmental factors, the purpose was to examine the extent to which these species-level patterns are integrated into a framework determined by the annual inundation, a seasonal aspect in an otherwise relatively aseasonal forest.
The data consists of monthly observations of flowering, fruiting and leaf habits of 312 individuals over a period of 12 years. Circular vector statistics was used to study the periodicity and timing of phenological patterns for each species. Seasonality and relationships with climatic factors revealed by time series (cross correlation) analyses are discussed at both the community and population levels.
More 60% of the species presented annual and synchronous flowering which occurred just before the heavy wet season, somewhat later than dry season flowering found in other tropical forests. This adjustment in flowering time allowed all but 1 species to time their fruiting to fall in the aquatic phase just after.
Little evidence was found for flooding causing a 'physiological winter' or high stress for the species studied ; leaf flush (growth) and reproductive activity did not stagnate throughout the inundated period and leaf fall is not directly related to highest water levels. Rather, flooding appears to have an impact with regard to use for seed dispersal by fish and water for the zoochorous species and for all species as a strategy to time dispersal and germination in optimal conditions and ensure that vulnerable seedlings have time to grow before the onset of next flooded phase.

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