Phenology and production of litter in a Pterocarpus officinalis (Jacq.) swamp forest of Guadeloupe (Lesser Antilles)

The Pterocarpus officinalis swamp forest is the main type of forest in freshwater to slightly brackish wetlands in the Antilles. The objective of this study was to evaluate the impact of spatial variation in flooding on litterfall. Four plots of 400 m2 were staked out in three stands distributed along a flooding gradient in a 100-ha forest track located in Guadeloupe (Lesser Antilles). The structure of the vegetation was characterized in each plot (basal area, density, stand height). Fine litterfall was monitored fortnightly during 24 months using forty-eight 0.5-m2 litter traps. Water-table level, groundwater salinity and climatic conditions were measured at every collection. Coarse litterfall (fallen trunks and branches, Ø > 3 cm) was measured every six months on four 100-m2 subplots in each stand. Regarding fine litterfall (from 10.5 to 14.2 Mg ha−1 y−1 on the study site), the P. officinalis swamp forest appeared to be the most productive forest ecosystem in Guadeloupe and probably also in the whole of the Lesser Antilles. Coarse litterfall ranged from 12 to 20% of total litterfall. Litter production was highest in the most flooded stand which was a tall, almost pure P. officinalis stand. Despite episodic disturbances caused by violent climatic events such as hurricanes, the phenology of the canopy was characterized by the alternation of higher leaf fall during the dry season and massive blooming and fruiting during the rainy season. The phenology of the hemi-parasitic species Psittacanthus martinicensis contrasted with that of the canopy trees making the flowers of this species more visible to pollinators. The relative litter production and the fructification success rate of P. officinalis were lowest in the least flooded stand, suggesting a lower competitiveness of this species on higher grounds. Despite the presence of water at root level, P. officinalis seems to be very sensitive to parching atmospheric conditions. Conversely, its outstanding capacity to cope with high water levels and to store organic carbon in swamp sediments may lend these swamps a promising role in carbon sequestration.

► We evaluate litter production in a Pterocarpus officinalis swamp forest.
► Fine wood production is greater than in the other forests of the Lesser Antilles.
► Deep flooding conditions enhance P. officinalis’ production of leaves and fruits.
► Seasonal peaks of leaf litter are associated to high evapotranspiration conditions.